LLVM-DEBUGINFO-ANALYZER(1)
💅 llvm-debuginfo-analyzer — the LLVM man page, but make it make sense
okay bestie, welcome to the llvm-debuginfo-analyzer(1) page 💖 this is the LLVM tool that prints a logical representation of low-level debug information, and yes she is a lot, but she's also iconic. grab a snack, we're doing this together 🍓
🎀 WHAT'S INSIDE (table of contents, fr)
- SYNOPSIS
- DESCRIPTION
- OPTIONS
- GENERAL
- ATTRIBUTES
- OUTPUT
- REPORT
- SELECTION
- ELEMENTS
- LINES
- SCOPES
- SYMBOLS
- TYPES
- COMPARE
- WARNING
- INTERNAL
- EXAMPLES
- TEST CASE 1 - GENERAL OPTIONS
- PRINTING MODE
- BASIC DETAILS
- SELECT LOGICAL ELEMENTS
- COMPARISON MODE
- LOGICAL VIEW
- LOGICAL ELEMENTS
- PRINTING MODE
- TEST CASE 2 - ASSEMBLER INSTRUCTIONS
- CodeView - Clang (Windows)
- CodeView - MSVC (Windows)
- DWARF - Clang (Linux)
- DWARF - GCC (Linux)
- TEST CASE 3 - INCORRECT LEXICAL SCOPE FOR TYPEDEF
- CodeView - Clang (Windows)
- CodeView - MSVC (Windows)
- DWARF - Clang (Linux)
- DWARF - GCC (Linux)
- TEST CASE 4 - MISSING NESTED ENUMERATIONS
- CodeView - Clang (Windows)
- CodeView - MSVC (Windows)
- DWARF - Clang (Linux)
- DWARF - GCC (Linux)
- TEST CASE 5 - INCORRECT LEXICAL SCOPE FOR VARIABLE
- CODEVIEW - Clang (Windows)
- CODEVIEW - MSVC (Windows)
- DWARF - Clang (Linux)
- DWARF - GCC (Linux)
- TEST CASE 6 - FULL LOGICAL VIEW
- WEBASSEMBLY SUPPORT
- PRINT BASIC DETAILS
- SELECT LOGICAL ELEMENTS
- LLVM IR (textual / bitcode representation) SUPPORT
- PRINT BASIC DETAILS
- TEST CASE 1 - GENERAL OPTIONS
- EXIT STATUS
- LIMITATIONS AND KNOWN ISSUES
- SEE ALSO
✨ SYNOPSIS ✨
like, the whole vibe in one line:
llvm-debuginfo-analyzer [options] [filename ...]🦋 DESCRIPTION
so. llvm-debuginfo-analyzer parses debug and text sections in binary object files or in LLVM IR textual / bitcode representation, and then prints their contents in a logical view — which is a human readable representation that closely matches the structure of the original user source code. no cap. Supported object file formats include ELF, Mach-O, WebAssembly, PDB, COFF and IR (textual representation and bitcode) 👑
The logical view abstracts the complexity associated with the different low-level representations of the debugging information that is embedded in the object file. llvm-debuginfo-analyzer produces a canonical view of the debug information regardless of how it is formatted. The same logical view will be seen regardless of object file format, assuming the debug information correctly represents the same original source code. it's giving consistency 💅
The logical view includes the following logical elements: type, scope, symbol and line — which are the basic software elements used in the C/C++ programming language. Each logical element has a set of attributes, such as types, classes, functions, variables, parameters, etc. The --attribute option can be used to specify which attributes to include when printing a logical element. A logical element may have a kind that describes specific types of elements. For instance, a scope could have a kind value of function, class, namespace. yep, she has range 🌈
llvm-debuginfo-analyzer defaults to printing a pre-defined layout of logical elements and attributes. The command line options can be used to control the printed elements (--print), using a specific layout (--report), matching a given pattern (--select, --select-offsets). Also, the output can be limited to specified logical elements using (--select-lines, --select-scopes, --select-symbols, --select-types).
llvm-debuginfo-analyzer can also compare a set of logical views (--compare), to find differences and identify possible debug information syntax issues (--warning) in any object file. detective mode fr 🔍
💖 OPTIONS 💖
llvm-debuginfo-analyzer options are separated into several categories, each tailored to a different purpose:
- GENERAL — Standard LLVM options to display help, version, etc.
- ATTRIBUTES — Describe how to include different details when printing an element.
- PRINT — Specify which elements will be included when printing the view.
- OUTPUT — Describe the supported formats when printing the view.
- REPORT — Describe the format layouts for view printing.
- SELECTION — Allows to use specific criteria or conditions to select which elements to print.
- COMPARE — Compare logical views and print missing and/or added elements.
- WARNING — Print the warnings detected during the creation of the view.
- INTERNAL — Internal analysis of the logical view.
🌸 GENERAL
This section describes the standard help options, used to display the usage, version, response files, etc. the boring-but-essential starter pack 🫶
-h,--help— Show help and usage for this command. (--help-hiddenfor more).--help-list— Show help and usage for this command without grouping the options into categories (--help-list-hiddenfor more).--help-hidden— Display all available options.--print-all-options— Print all option values after command line parsing.--print-options— Print non-default options after command line parsing--version— Display the version of the tool.@<FILE>— Read command-line options from<FILE>.
If no input file is specified, llvm-debuginfo-analyzer defaults to read a.out and return an error when no input file is found. she assumes, and she will let you know 😭
If - is used as the input file, llvm-debuginfo-analyzer reads the input from its standard input stream. slay, pipe it straight in 💜
🧚 ATTRIBUTES
The following options enable attributes given for the printed elements. The attributes are divided in categories based on the type of data being added, such as: internal offsets in the binary file, location descriptors, register names, user source filenames, additional element transformations, toolchain name, binary file format, etc.
--attribute=<value[,value,...]>— Withvaluebeing one of the options in the following lists.
=all: Include all the below attributes.
=extended: Add low-level attributes.
=standard: Add standard high-level attributes.The following attributes describe the most common information for a logical element. They help to identify the lexical scope level; the element visibility across modules (global, local); the toolchain name and source language that produced the binary file.
=global— Element referenced across Compile Units.=format— Object file format name.=language— Source language name.=level— Lexical scope level (File=0, Compile Unit=1).=local— Element referenced only in the Compile Unit.=producer— Toolchain identification name.
The following attributes describe files and directory names from the user source code, where the elements are declared or defined; functions with public visibility across modules. These options allow to map the elements to their user code location, for cross references purposes. iykyk 🔥
=directories— Directories referenced in the debug information.=filename— Filename where the element is defined.=files— Files referenced in the debug information.=pathname— Pathname where the object is defined.=publics— Function names that are public.
The following attributes describe additional logical element source transformations, in order to display built-in types (int, bool, etc.); parameters and arguments used during template instantiation; parent name hierarchy; array dimensions information; compiler generated elements; type sizes and the underlying types associated with the types aliases.
=argument— Template parameters replaced by its arguments.=base— Base types (int,bool, etc.).=generated— Compiler generated elements.=encoded— Template arguments encoded in the template name.=qualified— The element type include parents in its name.=reference— Element declaration and definition references.=size— Sizes for compound and base types.=subrange— Subrange encoding information for arrays.=typename— Template parameters.=underlying— Underlying type for type definitions.
The following attributes describe the debug location information for a symbol or scope. It includes the symbol percentage coverage and any gaps within the location layout; ranges determining the code sections attached to a function. When descriptors are used, the target processor registers are displayed.
=coverage— Symbol location coverage.=gaps— Missing debug location (gaps).=location— Symbol debug location.=range— Debug location ranges.=register— Processor register names.
The following attributes are associated with low level details, such as: offsets in the binary file; discriminators added to the lines of inlined functions in order to distinguish specific instances; debug lines state machine registers; elements discarded by the compiler (inlining) or by the linker optimizations (dead-stripping); system compile units generated by the MS toolchain in PDBs. deep lore 🕵️♀️
=discarded— Discarded elements by the linker.=discriminator— Discriminators for inlined function instances.=inserted— Generated inlined abstract references.=linkage— Object file linkage name.=offset— Debug information offset.=qualifier— Line qualifiers (Newstatement,BasicBlock, etc).=zero— Zero line numbers.
The following attribute described specific information for the PE/COFF file format. It includes MS runtime types.
=system— Display PDB's MS system elements.
The above attributes are grouped into standard and extended categories that can be enabled.
The standard group, contains those attributes that add sufficient information to describe a logical element and that can cover the normal situations while dealing with debug information.
=base
=coverage
=directories
=discriminator
=filename
=files
=format
=language
=level
=producer
=publics
=range
=reference
=zeroThe extended group is for the attributes that need a whole extra layer of debug-info knowledge to even make sense — reach for these when you want a lower level of detail. Here's the whole squad:
=argument=discarded=encoded=gaps=generated=global=inserted=linkage=local=location=offset=operation=pathname=qualified=qualifier=register=size=subrange=system=typename
🌸 PRINT 🌸
These options are all about which elements get printed. The layout you get is decided by --report — and heads up bestie, in the tree layout, every element gets its enclosing lexical scopes printed too, even the ones you didn't explicitly ask for. Surprise bonus content, iykyk 💅
--print=<value[,value,...]>— where value is one of the goodies in the lists right below 👇=all: Include all the below attributes.
Okay so the next batch prints the elements you actually asked for — and if you gave any select conditions (--select), only the elements that match them get printed. The elements value is the lazy-girl shortcut that grabs instructions, lines, scopes, symbols and types all at once. Slay.
=elements: Instructions, lines, scopes, symbols and types.=instructions: Assembler instructions for code sections.=lines: Source lines referenced in the debug information.=scopes: Lexical blocks (function, class, namespace, etc).=symbols: Symbols (variable, member, parameter, etc).=types: Types (pointer, reference, type alias, etc).
Then these ones print the meta info — the stuff collected while the elements were being created. Think: scope contributions to the debug information, a summary of elements created / printed / matched (--select), and any warnings that popped up during view creation.
=sizes: Debug Information scopes contributions.=summary: Summary of elements allocated, selected or printed.=warnings: Warnings detected.
Heads up 🫶 — the --print=sizes option is ELF specific. Don't come for me if it ghosts you on other formats.
🎀 OUTPUT 🎀
Now we're talking about how to control the output generated when printing the logical elements. Vibe curation, essentially ✨
--output-file=<path>— Redirect the output to a file specified by<path>, where-is the standard output stream.
Okay so llvm-debuginfo-analyzer has this whole concept of a split view. When you redirect the output from a complex binary format, it gets divided into individual files, and each one holds the logical view output for a single compilation unit. One file per CU, very organized, very main-character 💅
--output-folder=<name>— The folder to write a file per compilation unit when--output=splitis specified.--output-level=<level>— Only print elements up to the given lexical level value. The input file is at lexical level zero and a compilation unit is at lexical level one. (so yes, the binary is level 0, the CU is level 1, keep counting from there 🪜)--output=<value[,value,...]>— where value is one of these:=all: Include all the below outputs.=json: Use JSON as the output format (Not implemented). 😭 yeah it's not a thing yet, don't @ me=split: Split the output by Compile Units.=text: Use a free form text output.
--output-sort=<key>— Primary key when ordering the elements in the output (default:line). Sorting by logical element kind requires be familiarity with the element kind selection options (--select-lines,--select-scopes,--select-symbols,--select-types), because those options describe the different logical element kinds. (yes, "requires be familiarity" — the manpage said it, I'm just the messenger 🙈)=none: Unsorted output (i.e. as read from input).=id: Sort by unique element ID.=kind: Sort by element kind.=line: Sort by element line number.=name: Sort by element name.=offset: Sort by element offset.
🦋 REPORT 🦋
Depending on the task being executed (print, compare, select), several layouts are supported to display the elements in a more suitable way — all to make the output easier to understand. Aesthetic and functional, we love to see it 💖
--report=<value[,value,...]>— where value is one of these:=all: Include all the below reports.=children: Elements and children are displayed in a tree format.=list: Elements are displayed in a tabular format.=parents: Elements and parents are displayed in a tree format.=view: Elements, parents and children are displayed in a tree format.
So, the list layout presents the logical elements in a tabular form without any parent-child relationship. Ngl this might be the preferred way to display elements that match specific conditions when you're comparing logical views — it makes differences way easier to spot. Very "where's waldo" but efficient 🕵️♀️
The children, parents and view layouts display elements in a tree format, with the scopes representing their nodes, and types, symbols, lines and other scopes representing the children. The layout shows the lexical scoping relationship between elements, with the binary file being the tree root (level 0) and each compilation unit being a child (level 1). It's giving family tree, but for debug info 🌳
- The children layout includes the elements that match any given criteria (
--select) or (--compare) and its children. - The parents layout includes the elements that match any given criteria (
--select) or (--compare) and its parents. - The combined view layout includes the elements that match any given criteria (
--select) or (--compare), its parents and children. The whole friend group, basically 👑
Notes, bestie, take notes 📝:
- When a selection criteria (
--select) is specified with no report option, the list layout is selected. - The comparison mode always uses the view layout.
💜 SELECTION 💜
When printing an element, different data can be included and it varies (--attribute) — from data directly associated with the binary file (offset) all the way to high level details like coverage, lexical scope level, location. And because the printed output can reach a considerable size, there are several selection options that enable printing of specific elements. Filtering is self-care, periodt ✨
The pattern matching can ignore the case (--select-nocase) and be extended to use regular expressions (--select-regex). Fancy.
🌈 ELEMENTS 🌈
These options allow printing of elements that match the given <pattern>, offset <value> or an element <condition>.
--select=<pattern>— Print all elements whose name or line number matches the given<pattern>.--select-offsets=<value[,value,...]>— Print all elements whose offset matches the given values. See--attributeoption.--select-elements=<condition[,condition,...]>— Print all elements that satisfy the given<condition>. With condition being one of these:=discarded: Discarded elements by the linker.=global: Element referenced across Compile Units.=optimized: Optimized inlined abstract references.
--select-nocase— Pattern matching is case-insensitive when using--select.--select-regex— Treat any<pattern>strings as regular expressions when selecting with--selectoption. If--select-nocaseis specified, the regular expression becomes case-insensitive.
If the <pattern> criteria is too general, a more selective option can be specified to target a particular category of elements: lines (‐ --select-lines), scopes (--select-scopes), symbols (--select-symbols) and types (--select-types).
Okay important caveat 🚨 — these options require knowledge of the debug information format (DWARF, CodeView), because the given kind describes a very specific type of element. Like, you gotta know your lore.
⭐ LINES ⭐
These options allow printing of lines that match the given <kind>. The given criteria describes the debug line state machine registers. Whole lotta machinery going on down there 🔧
--select-lines=<kind[,kind,...]>— with kind being one of:=AlwaysStepInto: marks an always step into.=BasicBlock: Marks a new basic block.=Discriminator: Line that has a discriminator.=EndSequence: Marks the end in the sequence of lines.=EpilogueBegin: Marks the start of a function epilogue.=LineAssembler: Lines that correspond to disassembly text.=LineDebug: Lines that correspond to debug lines.=NeverStepInto: marks a never step into.=NewStatement: Marks a new statement.=PrologueEnd: Marks the end of a function prologue.
🧚 SCOPES 🧚
These options allow printing of scopes that match the given <kind>. Buckle up, the list is long but she's worth it 💅
--select-scopes=<kind[,kind,...]>— with kind being one of:=Aggregate: A class, structure or union.=Array: An array.=Block: A generic block (lexical block or exception block).=CallSite: A call site.=CatchBlock: An exception block.=Class: A class.=CompileUnit: A compile unit.=EntryPoint: A subroutine entry point.=Enumeration: An enumeration.=Function: A function.=FunctionType: A function pointer.=InlinedFunction: An inlined function.=Label: A label.=LexicalBlock: A lexical block.=Module: A module.=Namespace: A namespace.=Root: The element representing the main scope.=Structure: A structure.=Subprogram: A subprogram.=Template: A template definition.=TemplateAlias: A template alias.=TemplatePack: A template pack.=TryBlock: An exception try block.=Union: A union.
🍓 SYMBOLS 🍓
These options allow printing of symbols that match the given <kind>.
--select-symbols=<kind[,kind,...]>— with kind being one of:=CallSiteParameter: A call site parameter.=Constant: A constant symbol.=Inheritance: A base class.=Member: A member class.=Parameter: A parameter to function.=Unspecified: Unspecified parameters to function.=Variable: A variable.
👑 TYPES 👑
These options allow printing of types that match the given <kind>.
--select-types=<kind[,kind,...]>— With kind being one of the options in the following list.
…and the class list wraps up with these, bestie — every single kind the analyzer knows about:
=Base— base type (integer, boolean, etc).=Const— constant specifier.=Enumerator— enumerator.=Import— import declaration.=ImportDeclaration— import declaration.=ImportModule— import module.=Pointer— pointer type.=PointerMember— pointer to member function.=Reference— reference type.=Restrict— restrict specifier.=RvalueReference— R-value reference.=Subrange— array subrange.=TemplateParam— template parameter.=TemplateTemplateParam— template template parameter.=TemplateTypeParam— template type parameter.=TemplateValueParam— template value parameter.=Typedef— type definition.=Unspecified— unspecified type.=Volatile— volatile specifier.
💅 COMPARE (yes, we're literally comparing, but make it semantic)
Okay so here's the situation. Sometimes printing out the elements is not the move. That's the case when what you actually care about is the fallout from different versions of the same toolchain, or what a specific compiler optimization did. Effects, not dumps.
In those moments, what we're looking for is which elements got added and which got removed. And because the debug information format is genuinely complicated, using a regular diff tool to find those elements is very difficult — impossible, even, when you're dealing with different debug formats. 💀
llvm-debuginfo-analyzer supports a logical element comparison, so you can find semantic differences between logical views — the kind produced by different toolchain versions or even different debug information formats. Slay.
One little honesty moment 🫶: when you compare logical views created from different debug formats, the accuracy depends on how closely the debug information represents the user code. For instance, a logical view created from a binary file with DWARF debug information may include more detailed data than a logical view created from a binary file with CodeView debug information.
The following options describe the elements to compare.
--compare=<value[,value,...]>— with value being one of the options in the list below:=all— include all the below elements.=lines— include lines.=scopes— include scopes.=symbols— include symbols.=types— include types.
So here's the cute part: llvm-debuginfo-analyzer takes the first binary file on the command line as the reference and the second one as the target. And to get a more descriptive report, the comparison is done twice — the reference and target views get swapped, so the report can show you those missing elements from the target view and those added elements to the reference view. Main character energy, honestly. ✨
See --report options on how to describe the comparison reports.
⚠️ WARNING (no like seriously, read this one)
When reading the input object files, llvm-debuginfo-analyzer can detect issues in the raw debug information. Now — these may not be considered fatal to the purpose of printing a logical view, but they can give you an indication about the quality and potentially expose issues with the generated debug information. 🫶
The following options describe the warnings to be recorded for later printing, if they are requested by --print.
--warning=<value[,value,...]>— with value being one of the options in the list below:=all— include all the below warnings.
The following options collect additional information during the creation of the logical view, to include invalid coverage values and locations for symbols; invalid code ranges; lines that are zero.
=coverages— invalid symbol coverages values.=lines— debug lines that are zero.=locations— invalid symbol locations.=ranges— invalid code ranges.
🔍 INTERNAL (peek behind the curtain, iykyk)
For a better understanding of the logical view, access to more detailed internal information could be needed. That kind of data would help you identify debug information processed, or spot incorrect logical element management. Typically these kinds of options are only available in debug builds — but llvm-debuginfo-analyzer supports these advanced options in both release and debug builds. Iconic. 👑
--internal=<value[,value,...]>— with value being one of the options in the list below:=all— include all the below options.
The following options allow you to check the integrity of the logical view; collect the debug tags that are processed or not implemented; ignore the logical element line number (to facilitate the logical view comparison when using external comparison tools); and print the command line options used to invoke llvm-debuginfo-analyzer.
=id— print unique element ID.=cmdline— print command line.=integrity— check elements integrity.=none— ignore element line number.=tag— debug information tags.
Note: for ELF format, the collected tags represent the debug tags that are not processed. For PE/COFF format, they represent the tags that are processed. 🧚
🌈 EXAMPLES (real files, real vibes)
This section includes some real binary files to show how to use llvm-debuginfo-analyzer to print a logical view and to diagnose possible debug information issues.
🧪 TEST CASE 1 - GENERAL OPTIONS
The below example is used to show different output generated by llvm-debuginfo-analyzer. We compiled the example for an X86 ELF target with Clang (-O0 -g):
1 using INTPTR = const int *;
2 int foo(INTPTR ParamPtr, unsigned ParamUnsigned, bool ParamBool) {
3 if (ParamBool) {
4 typedef int INTEGER;
5 const INTEGER CONSTANT = 7;
6 return CONSTANT;
7 }
8 return ParamUnsigned;
9 }🖨️ PRINTING MODE
In this mode llvm-debuginfo-analyzer prints the logical view — or portions of it — based on criteria patterns (including regular expressions) to select the kind of logical elements to be included in the output. ✨
🎀 BASIC DETAILS
The following command prints basic details for all the logical elements sorted by the debug information internal offset; it includes its lexical level and debug info format.
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=offset
--print=scopes,symbols,types,lines,instructions
test-dwarf-clang.oor
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=offset
--print=elements
test-dwarf-clang.oEach row represents an element that is present within the debug information. The first column represents the scope level, followed by the associated line number (if any), and finally the description of the element.
Logical View:
[000] {File} 'test-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'test.cpp'
[002] 2 {Function} extern not_inlined 'foo' -> 'int'
[003] 2 {Parameter} 'ParamPtr' -> 'INTPTR'
[003] 2 {Parameter} 'ParamUnsigned' -> 'unsigned int'
[003] 2 {Parameter} 'ParamBool' -> 'bool'
[003] {Block}
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'
[004] 5 {Line}
[004] {Code} 'movl $0x7, -0x1c(%rbp)'
[004] 6 {Line}
[004] {Code} 'movl $0x7, -0x4(%rbp)'
[004] {Code} 'jmp 0x6'
[004] 8 {Line}
[004] {Code} 'movl -0x14(%rbp), %eax'
[003] 4 {TypeAlias} 'INTEGER' -> 'int'
[003] 2 {Line}
[003] {Code} 'pushq %rbp'
[003] {Code} 'movq %rsp, %rbp'
[003] {Code} 'movb %dl, %al'
[003] {Code} 'movq %rdi, -0x10(%rbp)'
[003] {Code} 'movl %esi, -0x14(%rbp)'
[003] {Code} 'andb $0x1, %al'
[003] {Code} 'movb %al, -0x15(%rbp)'
[003] 3 {Line}
[003] {Code} 'testb $0x1, -0x15(%rbp)'
[003] {Code} 'je 0x13'
[003] 8 {Line}
[003] {Code} 'movl %eax, -0x4(%rbp)'
[003] 9 {Line}
[003] {Code} 'movl -0x4(%rbp), %eax'
[003] {Code} 'popq %rbp'
[003] {Code} 'retq'
[003] 9 {Line}
[002] 1 {TypeAlias} 'INTPTR' -> '* const int'On closer inspection, we can see what could be a potential debug issue:
[003] {Block}
[003] 4 {TypeAlias} 'INTEGER' -> 'int'The 'INTEGER' definition is at level [003], the same lexical scope as the anonymous {Block} ('true' branch for the 'if' statement) — whereas in the original source code the typedef statement is clearly inside that block, so the 'INTEGER' definition should also be at level [004] inside the block. 😭 (caught in 4K, fr fr)
🔎 SELECT LOGICAL ELEMENTS
The following prints all instructions, symbols and types that contain 'inte' or 'movl' in their names or types, using a tab layout and given the number of matches.
llvm-debuginfo-analyzer --attribute=level
--select-nocase --select-regex
--select=INTe --select=movl
--report=list
--print=symbols,types,instructions,summary
test-dwarf-clang.oLogical View:
[000] {File} 'test-dwarf-clang.o'
[001] {CompileUnit} 'test.cpp'
[003] {Code} 'movl $0x7, -0x1c(%rbp)'
[003] {Code} 'movl $0x7, -0x4(%rbp)'
[003] {Code} 'movl %eax, -0x4(%rbp)'
[003] {Code} 'movl %esi, -0x14(%rbp)'
[003] {Code} 'movl -0x14(%rbp), %eax'
[003] {Code} 'movl -0x4(%rbp), %eax'
[003] 4 {TypeAlias} 'INTEGER' -> 'int'
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'
-----------------------------
Element Total Found
-----------------------------
Scopes 3 0
Symbols 4 1
Types 2 1
Lines 17 6
-----------------------------
Total 26 8COMPARISON MODE 💖
In this mode llvm-debuginfo-analyzer compares logical views to produce a report with the logical elements that are missing or added. This is a very powerful aid in finding semantic differences in the debug information produced by different toolchain versions or even completely different toolchains altogether (for example a compiler producing DWARF can be directly compared against a completely different compiler that produces CodeView).
Given the previous example, we found the above debug information issue (related to the previous invalid scope location for the 'typedef int INTEGER') by comparing against another compiler.
Using GCC to generate test-dwarf-gcc.o, we can apply a selection pattern with the printing mode to obtain the following logical view output.
llvm-debuginfo-analyzer --attribute=level
--select-regex --select-nocase --select=INTe
--report=list
--print=symbols,types
test-dwarf-clang.o test-dwarf-gcc.oLogical View:
[000] {File} 'test-dwarf-clang.o'
[001] {CompileUnit} 'test.cpp'
[003] 4 {TypeAlias} 'INTEGER' -> 'int'
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'
Logical View:
[000] {File} 'test-dwarf-gcc.o'
[001] {CompileUnit} 'test.cpp'
[004] 4 {TypeAlias} 'INTEGER' -> 'int'
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'The output shows that both objects contain the same elements. But the 'typedef INTEGER' is located at different scope level. The GCC generated object, shows '4', which is the correct value.
Note that there is no requirement that GCC must produce identical or similar DWARF to Clang to allow the comparison. We're only comparing the semantics. The same case when comparing CodeView debug information generated by MSVC and Clang.
There are 2 comparison methods: logical view and logical elements.
LOGICAL VIEW 🦋
It compares the logical view as a whole unit; for a match, each compared logical element must have the same parents and children.
Using the llvm-debuginfo-analyzer comparison functionality, that issue can be seen in a more global context, that can include the logical view.
The output shows in view form the missing (-), added (+) elements, giving more context by swapping the reference and target object files.
llvm-debuginfo-analyzer --attribute=level
--compare=types
--report=view
--print=symbols,types
test-dwarf-clang.o test-dwarf-gcc.oReference: 'test-dwarf-clang.o'
Target: 'test-dwarf-gcc.o'
Logical View:
[000] {File} 'test-dwarf-clang.o'
[001] {CompileUnit} 'test.cpp'
[002] 1 {TypeAlias} 'INTPTR' -> '* const int'
[002] 2 {Function} extern not_inlined 'foo' -> 'int'
[003] {Block}
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'
+[004] 4 {TypeAlias} 'INTEGER' -> 'int'
[003] 2 {Parameter} 'ParamBool' -> 'bool'
[003] 2 {Parameter} 'ParamPtr' -> 'INTPTR'
[003] 2 {Parameter} 'ParamUnsigned' -> 'unsigned int'
-[003] 4 {TypeAlias} 'INTEGER' -> 'int'The output shows the merging view path (reference and target) with the missing and added elements.
LOGICAL ELEMENTS ✨
It compares individual logical elements without considering if their parents are the same. For both comparison methods, the equal criteria includes the name, source code location, type, lexical scope level.
llvm-debuginfo-analyzer --attribute=level
--compare=types
--report=list
--print=symbols,types,summary
test-dwarf-clang.o test-dwarf-gcc.oReference: 'test-dwarf-clang.o'
Target: 'test-dwarf-gcc.o'
(1) Missing Types:
-[003] 4 {TypeAlias} 'INTEGER' -> 'int'
(1) Added Types:
+[004] 4 {TypeAlias} 'INTEGER' -> 'int'
----------------------------------------
Element Expected Missing Added
----------------------------------------
Scopes 4 0 0
Symbols 0 0 0
Types 2 1 1
Lines 0 0 0
----------------------------------------
Total 6 1 1Changing the Reference and Target order:
llvm-debuginfo-analyzer --attribute=level
--compare=types
--report=list
--print=symbols,types,summary
test-dwarf-gcc.o test-dwarf-clang.oReference: 'test-dwarf-gcc.o'
Target: 'test-dwarf-clang.o'
(1) Missing Types:
-[004] 4 {TypeAlias} 'INTEGER' -> 'int'
(1) Added Types:
+[003] 4 {TypeAlias} 'INTEGER' -> 'int'
----------------------------------------
Element Expected Missing Added
----------------------------------------
Scopes 4 0 0
Symbols 0 0 0
Types 2 1 1
Lines 0 0 0
----------------------------------------
Total 6 1 1As the Reference and Target are switched, the Added Types from the first case now are listed as Missing Types.
TEST CASE 2 - ASSEMBLER INSTRUCTIONS 🧚
The below example is used to show different output generated by llvm-debuginfo-analyzer. We compiled the example for an X86 Codeview and ELF targets with recent versions of Clang, GCC and MSVC (-O0 -g) for Windows and Linux.
1 extern int printf(const char * format, ... );
2
3 int main()
4 {
5 printf("Hello, World\n");
6 return 0;
7 }These are the logical views that llvm-debuginfo-analyzer generates for 3 different compilers (MSVC, Clang and GCC), emitting different debug information formats (CodeView, DWARF) on Windows and Linux.
llvm-debuginfo-analyzer --attribute=level,format,producer
--print=lines,instructions
hello-world-codeview-clang.o
hello-world-codeview-msvc.o
hello-world-dwarf-clang.o
hello-world-dwarf-gcc.oCodeView - Clang (Windows) 🦋
Logical View:
[000] {File} 'hello-world-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'hello-world.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] {Function} extern not_inlined 'main' -> 'int'
[003] 4 {Line}
[003] {Code} 'subq $0x28, %rsp'
[003] {Code} 'movl $0x0, 0x24(%rsp)'
[003] 5 {Line}
[003] {Code} 'leaq (%rip), %rcx'
[003] {Code} 'callq 0x0'
[003] 6 {Line}
[003] {Code} 'xorl %eax, %eax'
[003] {Code} 'addq $0x28, %rsp'
[003] {Code} 'retq'CodeView - MSVC (Windows) 🎀
Logical View:
[000] {File} 'hello-world-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'hello-world.cpp'
[002] {Producer} 'Microsoft (R) Optimizing Compiler'
[002] {Function} extern not_inlined 'main' -> 'int'
[003] 4 {Line}
[003] {Code} 'pushl %ebp'
[003] {Code} 'movl %esp, %ebp'
[003] 5 {Line}
[003] {Code} 'pushl $0x0'
[003] {Code} 'calll 0x0'
[003] {Code} 'addl $0x4, %esp'
[003] 6 {Line}
[003] {Code} 'xorl %eax, %eax'
[003] 7 {Line}
[003] {Code} 'popl %ebp'
[003] {Code} 'retl'DWARF - Clang (Linux) 🌸
Logical View:
[000] {File} 'hello-world-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'hello-world.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] 3 {Function} extern not_inlined 'main' -> 'int'
[003] 4 {Line}
[003] {Code} 'pushq %rbp'
[003] {Code} 'movq %rsp, %rbp'
[003] {Code} 'subq $0x10, %rsp'
[003] {Code} 'movl $0x0, -0x4(%rbp)'
[003] 5 {Line}
[003] {Code} 'movabsq $0x0, %rdi'
[003] {Code} 'movb $0x0, %al'
[003] {Code} 'callq 0x0'
[003] 6 {Line}
[003] {Code} 'xorl %eax, %eax'
[003] {Code} 'addq $0x10, %rsp'
[003] {Code} 'popq %rbp'
[003] {Code} 'retq'
[003] 6 {Line}DWARF - GCC (Linux) 🍓
Logical View:
[000] {File} 'hello-world-dwarf-gcc.o' -> elf64-x86-64
[001] {CompileUnit} 'hello-world.cpp'
[002] {Producer} 'GNU C++14 9.3.0'
[002] 3 {Function} extern not_inlined 'main' -> 'int'
[003] 4 {Line}
[003] {Code} 'endbr64'
[003] {Code} 'pushq %rbp'
[003] {Code} 'movq %rsp, %rbp'
[003] 5 {Line}
[003] {Code} 'leaq (%rip), %rdi'
[003] {Code} 'movl $0x0, %eax'
[003] {Code} 'callq 0x0'
[003] 6 {Line}
[003] {Code} 'movl $0x0, %eax'
[003] 7 {Line}
[003] {Code} 'popq %rbp'
[003] {Code} 'retq'
[003] 7 {Line}The logical views shows the intermixed lines and assembler instructions, allowing to compare the code generated by the different toolchains.
TEST CASE 3 - INCORRECT LEXICAL SCOPE FOR TYPEDEF 🔥
The below example is used to show different output generated by llvm-debuginfo-analyzer. We compiled the example for an X86 Codeview and ELF targets with recent versions of Clang, GCC and MSVC (-O0 -g).
1 int bar(float Input) { return (int)Input; }
2
3 unsigned foo(char Param) {
4 typedef int INT; // ** Definition for INT **
5 INT Value = Param;
6 {
7 typedef float FLOAT; // ** Definition for FLOAT **
8 {
9 FLOAT Added = Value + Param;
10 Value = bar(Added);
11 }
12 }
13 return Value + Param;
14 }okay so this little snippet is the whole vibe behind a Clang scope issue, bestie: PR44884 (Bugs LLVM) / PR44229 (GitHub LLVM). no cap, it’s giving compiler detective work.
Lines 4 and 7 contain 2 typedefs, defined at different lexical scopes:
4 typedef int INT;
7 typedef float FLOAT;These are the logical views that llvm-debuginfo-analyzer generates for 3 different compilers (MSVC, Clang and GCC), emitting different debug information formats (CodeView, DWARF) on different platforms. the way this tool just spills the tea across formats is iconic 💅
llvm-debuginfo-analyzer --attribute=level,format,producer
--print=symbols,types,lines
--output-sort=kind
pr-44884-codeview-clang.o
pr-44884-codeview-msvc.o
pr-44884-dwarf-clang.o
pr-44884-dwarf-gcc.oCodeView - Clang (Windows) 🌸
Logical View:
[000] {File} 'pr-44884-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr-44884.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] {Function} extern not_inlined 'bar' -> 'int'
[003] {Parameter} 'Input' -> 'float'
[003] 1 {Line}
[002] {Function} extern not_inlined 'foo' -> 'unsigned'
[003] {Block}
[004] {Variable} 'Added' -> 'float'
[004] 9 {Line}
[004] 10 {Line}
[003] {Parameter} 'Param' -> 'char'
[003] {TypeAlias} 'FLOAT' -> 'float'
[003] {TypeAlias} 'INT' -> 'int'
[003] {Variable} 'Value' -> 'int'
[003] 3 {Line}
[003] 5 {Line}
[003] 13 {Line}CodeView - MSVC (Windows) 🎀
Logical View:
[000] {File} 'pr-44884-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr-44884.cpp'
[002] {Producer} 'Microsoft (R) Optimizing Compiler'
[002] {Function} extern not_inlined 'bar' -> 'int'
[003] {Variable} 'Input' -> 'float'
[003] 1 {Line}
[002] {Function} extern not_inlined 'foo' -> 'unsigned'
[003] {Block}
[004] {Block}
[005] {Variable} 'Added' -> 'float'
[004] {TypeAlias} 'FLOAT' -> 'float'
[004] 9 {Line}
[004] 10 {Line}
[003] {TypeAlias} 'INT' -> 'int'
[003] {Variable} 'Param' -> 'char'
[003] {Variable} 'Value' -> 'int'
[003] 3 {Line}
[003] 5 {Line}
[003] 13 {Line}
[003] 14 {Line}DWARF - Clang (Linux) 🦋
Logical View:
[000] {File} 'pr-44884-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-44884.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] 1 {Function} extern not_inlined 'bar' -> 'int'
[003] 1 {Parameter} 'Input' -> 'float'
[003] 1 {Line}
[003] 1 {Line}
[003] 1 {Line}
[002] 3 {Function} extern not_inlined 'foo' -> 'unsigned int'
[003] {Block}
[004] 9 {Variable} 'Added' -> 'FLOAT'
[004] 9 {Line}
[004] 9 {Line}
[004] 9 {Line}
[004] 9 {Line}
[004] 9 {Line}
[004] 10 {Line}
[004] 10 {Line}
[004] 10 {Line}
[004] 13 {Line}
[003] 3 {Parameter} 'Param' -> 'char'
[003] 7 {TypeAlias} 'FLOAT' -> 'float'
[003] 4 {TypeAlias} 'INT' -> 'int'
[003] 5 {Variable} 'Value' -> 'INT'
[003] 3 {Line}
[003] 5 {Line}
[003] 5 {Line}
[003] 13 {Line}
[003] 13 {Line}
[003] 13 {Line}
[003] 13 {Line}DWARF - GCC (Linux) 🌈
Logical View:
[000] {File} 'pr-44884-dwarf-gcc.o' -> elf32-littlearm
[001] {CompileUnit} 'pr-44884.cpp'
[002] {Producer} 'GNU C++14 10.2.1 20201103'
[002] 1 {Function} extern not_inlined 'bar' -> 'int'
[003] 1 {Parameter} 'Input' -> 'float'
[003] 1 {Line}
[003] 1 {Line}
[003] 1 {Line}
[002] 3 {Function} extern not_inlined 'foo' -> 'unsigned int'
[003] {Block}
[004] {Block}
[005] 9 {Variable} 'Added' -> 'FLOAT'
[005] 9 {Line}
[005] 9 {Line}
[005] 9 {Line}
[005] 10 {Line}
[005] 13 {Line}
[004] 7 {TypeAlias} 'FLOAT' -> 'float'
[003] 3 {Parameter} 'Param' -> 'char'
[003] 4 {TypeAlias} 'INT' -> 'int'
[003] 5 {Variable} 'Value' -> 'INT'
[003] 3 {Line}
[003] 5 {Line}
[003] 13 {Line}
[003] 14 {Line}
[003] 14 {Line}From the previous logical views, we can see that the Clang compiler emits both typedefs at the same lexical scope (3), which is wrong. GCC and MSVC emit correct lexical scope for both typedefs. Clang bestie, what is this behavior 😭
Using the llvm-debuginfo-analyzer selection facilities, we can produce a simple tabular output showing just the logical types that are Typedef. filtering era ✨
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=name
--select-types=Typedef
--report=list
--print=types
pr-44884-*.o Logical View:
[000] {File} 'pr-44884-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr_44884.cpp'
[003] {TypeAlias} 'FLOAT' -> 'float'
[003] {TypeAlias} 'INT' -> 'int' Logical View:
[000] {File} 'pr-44884-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr_44884.cpp'
[004] {TypeAlias} 'FLOAT' -> 'float'
[003] {TypeAlias} 'INT' -> 'int' Logical View:
[000] {File} 'pr-44884-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr_44884.cpp'
[003] 7 {TypeAlias} 'FLOAT' -> 'float'
[003] 4 {TypeAlias} 'INT' -> 'int' Logical View:
[000] {File} 'pr-44884-dwarf-gcc.o' -> elf32-littlearm
[001] {CompileUnit} 'pr_44884.cpp'
[004] 7 {TypeAlias} 'FLOAT' -> 'float'
[003] 4 {TypeAlias} 'INT' -> 'int'It also shows that the CodeView debug information does not generate source code line numbers for the those logical types. The logical view is sorted by the types name. iykyk, the sorting is doing its little moment 💫
TEST CASE 4 - MISSING NESTED ENUMERATIONS 💀
The below example is used to show different output generated by llvm-debuginfo-analyzer. We compiled the example for an X86 Codeview and ELF targets with recent versions of Clang, GCC and MSVC (-O0 -g). compiler sampling, but make it fashion 🧚
1 struct Struct {
2 union Union {
3 enum NestedEnum { RED, BLUE };
4 };
5 Union U;
6 };
7
8 Struct S;
9 int test() {
10 return S.U.BLUE;
11 }The above test is used to illustrate a scope issue found in the Clang compiler: PR46466 (Bugs LLVM) / PR45811 (GitHub LLVM). another Clang bug walk, let’s gooo 🔥
These are the logical views that llvm-debuginfo-analyzer generates for 3 different compilers (MSVC, Clang and GCC), emitting different debug information formats (CodeView, DWARF) on different platforms.
llvm-debuginfo-analyzer --attribute=level,format,producer
--output-sort=name
--print=symbols,types
pr-46466-codeview-clang.o
pr-46466-codeview-msvc.o
pr-46466-dwarf-clang.o
pr-46466-dwarf-gcc.oCodeView - Clang (Windows) 🌟
Logical View:
[000] {File} 'pr-46466-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] {Variable} extern 'S' -> 'Struct'
[002] 1 {Struct} 'Struct'
[003] {Member} public 'U' -> 'Union'
[003] 2 {Union} 'Union'
[004] 3 {Enumeration} 'NestedEnum' -> 'int'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'CodeView - MSVC (Windows) 🍓
Logical View:
[000] {File} 'pr-46466-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr-46466.cpp'
[002] {Producer} 'Microsoft (R) Optimizing Compiler'
[002] {Variable} extern 'S' -> 'Struct'
[002] 1 {Struct} 'Struct'
[003] {Member} public 'U' -> 'Union'
[003] 2 {Union} 'Union'
[004] 3 {Enumeration} 'NestedEnum' -> 'int'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'DWARF - Clang (Linux) 💜
Logical View:
[000] {File} 'pr-46466-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] 8 {Variable} extern 'S' -> 'Struct'
[002] 1 {Struct} 'Struct'
[003] 5 {Member} public 'U' -> 'Union'DWARF - GCC (Linux) 🫶
Logical View:
[000] {File} 'pr-46466-dwarf-gcc.o' -> elf64-x86-64
and the rest of that logical view is literally this, bestie:
[001] {CompileUnit} 'pr-46466.cpp'
[002] {Producer} 'GNU C++14 9.3.0'
[002] 8 {Variable} extern 'S' -> 'Struct'
[002] 1 {Struct} 'Struct'
[003] 5 {Member} public 'U' -> 'Union'
[003] 2 {Union} 'Union'
[004] 3 {Enumeration} 'NestedEnum' -> 'unsigned int'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'okay so from those previous logical views you can lowkey see the tea: the DWARF debug info generated by the Clang compiler does not include any references to the enumerators RED and BLUE. But the DWARF generated by GCC, plus the CodeView generated by Clang and MSVC? They do include those references. no cap.
using the llvm-debuginfo-analyzer selection facilities, we can produce a logical view showing just the logical types that are Enumerator and its parents. this logical view is sorted by the types name, periodt:
llvm-debuginfo-analyzer --attribute=format,level
--output-sort=name
--select-types=Enumerator
--report=parents
--print=types
pr-46466-*.oand the output is giving:
Logical View:
[000] {File} 'pr-46466-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
[002] 1 {Struct} 'Struct'
[003] 2 {Union} 'Union'
[004] 3 {Enumeration} 'NestedEnum' -> 'int'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'
Logical View:
[000] {File} 'pr-46466-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr-46466.cpp'
[002] 1 {Struct} 'Struct'
[003] 2 {Union} 'Union'
[004] 3 {Enumeration} 'NestedEnum' -> 'int'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'
Logical View:
[000] {File} 'pr-46466-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
Logical View:
[000] {File} 'pr-46466-dwarf-gcc.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
[002] 1 {Struct} 'Struct'
[003] 2 {Union} 'Union'
[004] 3 {Enumeration} 'NestedEnum' -> 'unsigned int'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'and using those selection facilities again, we can produce a simple tabular output with a summary for the logical types that are Enumerator. this logical view is sorted by the types name too:
llvm-debuginfo-analyzer --attribute=format,level
--output-sort=name
--select-types=Enumerator
--print=types,summary
pr-46466-*.owhich prints:
Logical View:
[000] {File} 'pr-46466-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'
-----------------------------
Element Total Found
-----------------------------
Scopes 5 0
Symbols 2 0
Types 6 2
Lines 0 0
-----------------------------
Total 13 2
Logical View:
[000] {File} 'pr-46466-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr-46466.cpp'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'
-----------------------------
Element Total Found
-----------------------------
Scopes 5 0
Symbols 2 0
Types 7 2
Lines 0 0
-----------------------------
Total 14 2
Logical View:
[000] {File} 'pr-46466-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
-----------------------------
Element Total Found
-----------------------------
Scopes 4 0
Symbols 0 0
Types 0 0
Lines 0 0
-----------------------------
Total 4 0
Logical View:
[000] {File} 'pr-46466-dwarf-gcc.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-46466.cpp'
[005] {Enumerator} 'BLUE' = '0x1'
[005] {Enumerator} 'RED' = '0x0'
-----------------------------
Element Total Found
-----------------------------
Scopes 5 0
Symbols 0 0
Types 2 2
Lines 0 0
-----------------------------
Total 7 2from the values printed under the Found column, you can see that no Types were found in the DWARF debug information generated by Clang. it's giving "empty, bestie." 😭
💅 TEST CASE 5 - INCORRECT LEXICAL SCOPE FOR VARIABLE 💅
the example below is used to show the different output generated by llvm-debuginfo-analyzer. we compiled the example for an X86 Codeview and ELF targets with recent versions of Clang, GCC and MSVC (-O0 -g). okay so, housekeeping:
// definitions.h
#ifdef _MSC_VER
#define forceinline __forceinline
#elif defined(__clang__)
#if __has_attribute(__always_inline__)
#define forceinline inline __attribute__((__always_inline__))
#else
#define forceinline inline
#endif
#elif defined(__GNUC__)
#define forceinline inline __attribute__((__always_inline__))
#else
#define forceinline inline
#error
#endifsince the test is dependent on inline compiler options, the header file above defines forceinline, slay:
#include "definitions.h"
1 #include "definitions.h"
2 forceinline int InlineFunction(int Param) {
3 int Var_1 = Param;
4 {
5 int Var_2 = Param + Var_1;
6 Var_1 = Var_2;
7 }
8 return Var_1;
9 }
10
11 int test(int Param_1, int Param_2) {
12 int A = Param_1;
13 A += InlineFunction(Param_2);
14 return A;
15 }the test above is used to illustrate a variable issue found in the Clang compiler: PR43860 (Bugs LLVM) / PR43205 (GitHub). not me being dramatic, it's literally in the source.
these are the logical views that llvm-debuginfo-analyzer generates for 3 different compilers (MSVC, Clang and GCC), emitting different debug information formats (CodeView, DWARF) on different platforms:
llvm-debuginfo-analyzer --attribute=level,format,producer
--output-sort=name
--print=symbols
pr-43860-codeview-clang.o
pr-43860-codeview-msvc.o
pr-43860-dwarf-clang.o
pr-43860-dwarf-gcc.oCODEVIEW - Clang (Windows)
Logical View:
[000] {File} 'pr-43860-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr-43860.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] 2 {Function} inlined 'InlineFunction' -> 'int'
[003] {Parameter} '' -> 'int'
[002] {Function} extern not_inlined 'test' -> 'int'
[003] {Variable} 'A' -> 'int'
[003] {InlinedFunction} inlined 'InlineFunction' -> 'int'
[004] {Parameter} 'Param' -> 'int'
[004] {Variable} 'Var_1' -> 'int'
[004] {Variable} 'Var_2' -> 'int'
[003] {Parameter} 'Param_1' -> 'int'
[003] {Parameter} 'Param_2' -> 'int'CODEVIEW - MSVC (Windows)
Logical View:
[000] {File} 'pr-43860-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr-43860.cpp'
[002] {Producer} 'Microsoft (R) Optimizing Compiler'
[002] {Function} extern not_inlined 'InlineFunction' -> 'int'
[003] {Block}
[004] {Variable} 'Var_2' -> 'int'
[003] {Variable} 'Param' -> 'int'
[003] {Variable} 'Var_1' -> 'int'
[002] {Function} extern not_inlined 'test' -> 'int'
[003] {Variable} 'A' -> 'int'
[003] {Variable} 'Param_1' -> 'int'
[003] {Variable} 'Param_2' -> 'int'DWARF - Clang (Linux)
Logical View:
[000] {File} 'pr-43860-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-43860.cpp'
[002] {Producer} 'clang version 14.0.0'
[002] 2 {Function} extern inlined 'InlineFunction' -> 'int'
[003] {Block}
[004] 5 {Variable} 'Var_2' -> 'int'
[003] 2 {Parameter} 'Param' -> 'int'
[003] 3 {Variable} 'Var_1' -> 'int'
[002] 11 {Function} extern not_inlined 'test' -> 'int'
[003] 12 {Variable} 'A' -> 'int'
[003] 13 {InlinedFunction} inlined 'InlineFunction' -> 'int'
[004] {Block}
[005] {Variable} 'Var_2' -> 'int'
[004] {Parameter} 'Param' -> 'int'
[004] {Variable} 'Var_1' -> 'int'
[003] 11 {Parameter} 'Param_1' -> 'int'
[003] 11 {Parameter} 'Param_2' -> 'int'DWARF - GCC (Linux)
Logical View:
[000] {File} 'pr-43860-dwarf-gcc.o' -> elf64-x86-64 [001] {CompileUnit} 'pr-43860.cpp'
[002] {Producer} 'GNU C++14 9.3.0'
[002] 2 {Function} extern declared_inlined 'InlineFunction' -> 'int'
[003] {Block}
[004] 5 {Variable} 'Var_2' -> 'int'
[003] 2 {Parameter} 'Param' -> 'int'
[003] 3 {Variable} 'Var_1' -> 'int'
[002] 11 {Function} extern not_inlined 'test' -> 'int'
[003] 12 {Variable} 'A' -> 'int'
[003] 13 {InlinedFunction} declared_inlined 'InlineFunction' -> 'int'
[004] {Block}
[005] {Variable} 'Var_2' -> 'int'
[004] {Parameter} 'Param' -> 'int'
[004] {Variable} 'Var_1' -> 'int'
[003] 11 {Parameter} 'Param_1' -> 'int'
[003] 11 {Parameter} 'Param_2' -> 'int'So if you eyeball those logical views above 👀 — the CodeView debug info that the Clang compiler spits out is putting the variables Var_1 and Var_2 at the same lexical scope (4) inside the function InlineFuction. Meanwhile the DWARF from GCC/Clang and the CodeView from MSVC both put those variables at the correct lexical scope: 3 and 4 respectively. Bestie, that's a whole red flag for the Clang CodeView path 🚩😭
And here's the glow-up: using the llvm-debuginfo-analyzer selection facilities, we can produce a simple tabular output showing just the logical elements that have in their name the var pattern. The logical view is sorted by the variables name. Chef's kiss, honestly ✨
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=name
--select-regex --select-nocase --select=Var
--report=list
--print=symbols
pr-43860-*.oLogical View:
[000] {File} 'pr-43860-codeview-clang.o' -> COFF-x86-64
[001] {CompileUnit} 'pr-43860.cpp'
[004] {Variable} 'Var_1' -> 'int'
[004] {Variable} 'Var_2' -> 'int'
Logical View:
[000] {File} 'pr-43860-codeview-msvc.o' -> COFF-i386
[001] {CompileUnit} 'pr-43860.cpp'
[003] {Variable} 'Var_1' -> 'int'
[004] {Variable} 'Var_2' -> 'int'
Logical View:
[000] {File} 'pr-43860-dwarf-clang.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-43860.cpp'
[004] {Variable} 'Var_1' -> 'int'
[003] 3 {Variable} 'Var_1' -> 'int'
[005] {Variable} 'Var_2' -> 'int'
[004] 5 {Variable} 'Var_2' -> 'int'
Logical View:
[000] {File} 'pr-43860-dwarf-gcc.o' -> elf64-x86-64
[001] {CompileUnit} 'pr-43860.cpp'
[004] {Variable} 'Var_1' -> 'int'
[003] 3 {Variable} 'Var_1' -> 'int'
[005] {Variable} 'Var_2' -> 'int'
[004] 5 {Variable} 'Var_2' -> 'int'It also shows that the CodeView debug information does not generate source code line numbers for those logical symbols 💀 The logical view is sorted by the types name.
🦋 TEST CASE 6 - FULL LOGICAL VIEW 🦋
Okay for the advanced users in the chat — llvm-debuginfo-analyzer can display low level information that includes offsets within the debug information section, debug location operands, linkage names, etc. This is the main character energy view, ngl 🔥
llvm-debuginfo-analyzer --attribute=all
--print=all
test-dwarf-clang.oLogical View:
[0x0000000000][000] {File} 'test-dwarf-clang.o' -> elf64-x86-64
[0x000000000b][001] {CompileUnit} 'test.cpp'
[0x000000000b][002] {Producer} 'clang version 12.0.0'
{Directory} ''
{File} 'test.cpp'
{Public} 'foo' [0x0000000000:0x000000003a]
[0x000000000b][002] {Range} Lines 2:9 [0x0000000000:0x000000003a]
[0x00000000bc][002] {BaseType} 'bool'
[0x0000000099][002] {BaseType} 'int'
[0x00000000b5][002] {BaseType} 'unsigned int'
[0x00000000a0][002] {Source} '/test.cpp'
[0x00000000a0][002] 1 {TypeAlias} 'INTPTR' -> [0x00000000ab]'* const int'
[0x000000002a][002] 2 {Function} extern not_inlined 'foo' -> [0x0000000099]'int'
[0x000000002a][003] {Range} Lines 2:9 [0x0000000000:0x000000003a]
[0x000000002a][003] {Linkage} 0x2 '_Z3fooPKijb'
[0x0000000071][003] {Block}
[0x0000000071][004] {Range} Lines 5:8 [0x000000001c:0x000000002f]
[0x000000007e][004] 5 {Variable} 'CONSTANT' -> [0x00000000c3]'const INTEGER'
[0x000000007e][005] {Coverage} 100.00%
[0x000000007f][005] {Location}
[0x000000007f][006] {Entry} Stack Offset: -28 (0xffffffffffffffe4) [DW_OP_fbreg]
[0x000000001c][004] 5 {Line} {NewStatement} '/test.cpp'
[0x000000001c][004] {Code} 'movl $0x7, -0x1c(%rbp)'
[0x0000000023][004] 6 {Line} {NewStatement} '/test.cpp'
[0x0000000023][004] {Code} 'movl $0x7, -0x4(%rbp)'
[0x000000002a][004] {Code} 'jmp 0x6'
[0x000000002f][004] 8 {Line} {NewStatement} '/test.cpp'
[0x000000002f][004] {Code} 'movl -0x14(%rbp), %eax'
[0x0000000063][003] 2 {Parameter} 'ParamBool' -> [0x00000000bc]'bool'
[0x0000000063][004] {Coverage} 100.00%
[0x0000000064][004] {Location}
[0x0000000064][005] {Entry} Stack Offset: -21 (0xffffffffffffffeb) [DW_OP_fbreg]
[0x0000000047][003] 2 {Parameter} 'ParamPtr' -> [0x00000000a0]'INTPTR'
[0x0000000047][004] {Coverage} 100.00%
[0x0000000048][004] {Location}
[0x0000000048][005] {Entry} Stack Offset: -16 (0xfffffffffffffff0) [DW_OP_fbreg]
[0x0000000055][003] 2 {Parameter} 'ParamUnsigned' -> [0x00000000b5]'unsigned int'
[0x0000000055][004] {Coverage} 100.00%
[0x0000000056][004] {Location}
[0x0000000056][005] {Entry} Stack Offset: -20 (0xffffffffffffffec) [DW_OP_fbreg]
[0x000000008d][003] 4 {TypeAlias} 'INTEGER' -> [0x0000000099]'int'
[0x0000000000][003] 2 {Line} {NewStatement} '/test.cpp'
[0x0000000000][003] {Code} 'pushq %rbp'
[0x0000000001][003] {Code} 'movq %rsp, %rbp'
[0x0000000004][003] {Code} 'movb %dl, %al'
[0x0000000006][003] {Code} 'movq %rdi, -0x10(%rbp)'
[0x000000000a][003] {Code} 'movl %esi, -0x14(%rbp)'
[0x000000000d][003] {Code} 'andb $0x1, %al'
[0x000000000f][003] {Code} 'movb %al, -0x15(%rbp)'
[0x0000000012][003] 3 {Line} {NewStatement} {PrologueEnd} '/test.cpp'
[0x0000000012][003] {Code} 'testb $0x1, -0x15(%rbp)'
[0x0000000016][003] {Code} 'je 0x13'
[0x0000000032][003] 8 {Line} '/test.cpp'
[0x0000000032][003] {Code} 'movl %eax, -0x4(%rbp)'
[0x0000000035][003] 9 {Line} {NewStatement} '/test.cpp'
[0x0000000035][003] {Code} 'movl -0x4(%rbp), %eax'
[0x0000000038][003] {Code} 'popq %rbp'
[0x0000000039][003] {Code} 'retq'
[0x000000003a][003] 9 {Line} {NewStatement} {EndSequence} '/test.cpp'
-----------------------------
Element Total Printed
-----------------------------
Scopes 3 3
Symbols 4 4
Types 5 5
Lines 25 25
-----------------------------
Total 37 37
Scope Sizes:
189 (100.00%) : [0x000000000b][001] {CompileUnit} 'test.cpp'
110 ( 58.20%) : [0x000000002a][002] 2 {Function} extern not_inlined 'foo' -> [0x0000000099]'int'
27 ( 14.29%) : [0x0000000071][003] {Block}
Totals by lexical level:
[001]: 189 (100.00%)
[002]: 110 ( 58.20%)
[003]: 27 ( 14.29%)The Scope Sizes table shows the contribution in bytes to the debug information by each scope, which can be used to determine unexpected size changes in the DWARF sections between different versions of the same toolchain. Like, it's literally the vibe check for your debug info across toolchain upgrades 📈
[0x000000002a][002] 2 {Function} extern not_inlined 'foo' -> [0x0000000099]'int'
[0x000000002a][003] {Range} Lines 2:9 [0x0000000000:0x000000003a]
[0x000000002a][003] {Linkage} 0x2 '_Z3fooPKijb'
[0x0000000071][003] {Block}
[0x0000000071][004] {Range} Lines 5:8 [0x000000001c:0x000000002f]
[0x000000007e][004] 5 {Variable} 'CONSTANT' -> [0x00000000c3]'const INTEGER'
[0x000000007e][005] {Coverage} 100.00%
[0x000000007f][005] {Location}
[0x000000007f][006] {Entry} Stack Offset: -28 (0xffffffffffffffe4) [DW_OP_fbreg]The {Range} attribute describes the line ranges for a logical scope. For this case, the function foo is within the lines 2 and 9 🎯
The {Coverage} and {Location} attributes describe the debug location and coverage for logical symbols. Heads up though — for optimized code, the coverage value decreases and it affects the program debuggability. Not a cute look, but that's the tradeoff 😬
🌐 WEBASSEMBLY SUPPORT 🌐
The below example is used to show the WebAssembly output generated by llvm-debuginfo-analyzer. We compiled the example for a WebAssembly 32-bit target with Clang (-O0 -g --target=wasm32) 🧚
1 using INTPTR = const int *;
2 int foo(INTPTR ParamPtr, unsigned ParamUnsigned, bool ParamBool) {
3 if (ParamBool) {
4 typedef int INTEGER;
5 const INTEGER CONSTANT = 7;
6 return CONSTANT;
7 }
8 return ParamUnsigned;
9 }💅 PRINT BASIC DETAILS 💅
The following command prints basic details for all the logical elements sorted by the debug information internal offset; it includes its lexical level and debug info format. Simple, clean, slays ✨
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=offset
--print=scopes,symbols,types,lines,instructions
test-clang.oor
okay bestie, we’re still in the example zone — this command is literally continuing the previous bit:
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=offset
--print=elements
test-clang.oEvery row is one element that’s present within the debug information. First column = scope level, then the associated line number if there is one, then the description of the element. No cap:
Logical View:
[000] {File} 'test-clang.o' -> WASM
[001] {CompileUnit} 'test.cpp'
[002] 2 {Function} extern not_inlined 'foo' -> 'int'
[003] 2 {Parameter} 'ParamPtr' -> 'INTPTR'
[003] 2 {Parameter} 'ParamUnsigned' -> 'unsigned int'
[003] 2 {Parameter} 'ParamBool' -> 'bool'
[003] {Block}
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'
[004] 5 {Line}
[004] {Code} 'i32.const 7'
[004] {Code} 'local.set 10'
[004] {Code} 'local.get 5'
[004] {Code} 'local.get 10'
[004] {Code} 'i32.store 12'
[004] 6 {Line}
[004] {Code} 'i32.const 7'
[004] {Code} 'local.set 11'
[004] {Code} 'local.get 5'
[004] {Code} 'local.get 11'
[004] {Code} 'i32.store 28'
[004] {Code} 'br 1'
[004] - {Line}
[004] {Code} 'end'
[003] 4 {TypeAlias} 'INTEGER' -> 'int'
[003] 2 {Line}
[003] {Code} 'nop'
[003] {Code} 'end'
[003] {Code} 'i64.div_s'
[003] {Code} 'global.get 0'
[003] {Code} 'local.set 3'
[003] {Code} 'i32.const 32'
[003] {Code} 'local.set 4'
[003] {Code} 'local.get 3'
[003] {Code} 'local.get 4'
[003] {Code} 'i32.sub'
[003] {Code} 'local.set 5'
[003] {Code} 'local.get 5'
[003] {Code} 'local.get 0'
[003] {Code} 'i32.store 24'
[003] {Code} 'local.get 5'
[003] {Code} 'local.get 1'
[003] {Code} 'i32.store 20'
[003] {Code} 'local.get 2'
[003] {Code} 'local.set 6'
[003] {Code} 'local.get 5'
[003] {Code} 'local.get 6'
[003] {Code} 'i32.store8 19'
[003] 3 {Line}
[003] {Code} 'local.get 5'
[003] {Code} 'i32.load8_u 19'
[003] {Code} 'local.set 7'
[003] 3 {Line}
[003] {Code} 'i32.const 1'
[003] {Code} 'local.set 8'
[003] {Code} 'local.get 7'
[003] {Code} 'local.get 8'
[003] {Code} 'i32.and'
[003] {Code} 'local.set 9'
[003] {Code} 'block'
[003] {Code} 'block'
[003] {Code} 'local.get 9'
[003] {Code} 'i32.eqz'
[003] {Code} 'br_if 0'
[003] 8 {Line}
[003] {Code} 'local.get 5'
[003] {Code} 'i32.load 20'
[003] {Code} 'local.set 12'
[003] 8 {Line}
[003] {Code} 'local.get 5'
[003] {Code} 'local.get 12'
[003] {Code} 'i32.store 28'
[003] - {Line}
[003] {Code} 'end'
[003] 9 {Line}
[003] {Code} 'local.get 5'
[003] {Code} 'i32.load 28'
[003] {Code} 'local.set 13'
[003] {Code} 'local.get 13'
[003] {Code} 'return'
[003] {Code} 'end'
[003] 9 {Line}
[003] {Code} 'unreachable'
[002] 1 {TypeAlias} 'INTPTR' -> '* const int'✨ SELECT LOGICAL ELEMENTS ✨
This next one prints every instruction, symbol, and type whose name or type contains 'block' or '.store' — tab layout included, plus the number of matches because we love receipts 💅:
llvm-debuginfo-analyzer --attribute=level
--select-nocase --select-regex
--select=BLOCK --select=.store
--report=list
--print=symbols,types,instructions,summary
test-clang.oLogical View:
[000] {File} 'test-clang.o'
[001] {CompileUnit} 'test.cpp'
[003] {Code} 'block'
[003] {Code} 'block'
[004] {Code} 'i32.store 12'
[003] {Code} 'i32.store 20'
[003] {Code} 'i32.store 24'
[004] {Code} 'i32.store 28'
[003] {Code} 'i32.store 28'
[003] {Code} 'i32.store8 19'
-----------------------------
Element Total Printed
-----------------------------
Scopes 3 0
Symbols 4 0
Types 2 0
Lines 62 8
-----------------------------
Total 71 8🦋 LLVM IR (textual / bitcode representation) SUPPORT 🦋
The example below shows the IR output generated by llvm-debuginfo-analyzer. We compiled it for an IR 64-bit target with Clang (-O0 -g --target=x86_64-linux):
1 using INTPTR = const int *;
2 int foo(INTPTR ParamPtr, unsigned ParamUnsigned, bool ParamBool) {
3 if (ParamBool) {
4 typedef int INTEGER;
5 const INTEGER CONSTANT = 7;
6 return CONSTANT;
7 }
8 return ParamUnsigned;
9 }💖 PRINT BASIC DETAILS 💖
This command prints basic details for all the logical elements, sorted by the debug information internal offset. It includes the lexical level and the debug info format. Two ways to get the same vibe:
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=offset
--print=scopes,symbols,types,lines,instructions
test-clang.llor
llvm-debuginfo-analyzer --attribute=level,format
--output-sort=offset
--print=elements
test-clang.llEach row is one element present within the debug information. First column = scope level, then the associated line number if there is one, then the description of the element. Iconic:
Logical View:
[000] {File} 'test-clang.ll' -> Textual IR
[001] {CompileUnit} 'test.cpp'
[002] 2 {Function} extern not_inlined 'foo' -> 'int'
[003] {Block}
[004] 5 {Variable} 'CONSTANT' -> 'const INTEGER'
[004] 5 {Line}
[004] {Code} 'store i32 7, ptr %CONSTANT, align 4, !dbg !32'
[004] 6 {Line}
[004] {Code} 'store i32 7, ptr %retval, align 4, !dbg !33'
[004] 6 {Line}
[004] {Code} 'br label %return, !dbg !33'
[003] 2 {Parameter} 'ParamPtr' -> 'INTPTR'
[003] 2 {Parameter} 'ParamUnsigned' -> 'unsigned int'
[003] 2 {Parameter} 'ParamBool' -> 'bool'
[003] 4 {TypeAlias} 'INTEGER' -> 'int'
[003] 2 {Line}
[003] {Code} '%retval = alloca i32, align 4'
[003] {Code} '%ParamPtr.addr = alloca ptr, align 8'
[003] {Code} '%ParamUnsigned.addr = alloca i32, align 4'
[003] {Code} '%ParamBool.addr = alloca i8, align 1'
[003] {Code} '%CONSTANT = alloca i32, align 4'
[003] {Code} 'store ptr %ParamPtr, ptr %ParamPtr.addr, align 8'
[003] {Code} 'store i32 %ParamUnsigned, ptr %ParamUnsigned.addr, align 4'
[003] {Code} '%storedv = zext i1 %ParamBool to i8'
[003] {Code} 'store i8 %storedv, ptr %ParamBool.addr, align 1'
[003] 8 {Line}
[003] {Code} '%1 = load i32, ptr %ParamUnsigned.addr, align 4, !dbg !34'
[003] 8 {Line}
[003] {Code} 'store i32 %1, ptr %retval, align 4, !dbg !35'
[003] 8 {Line}
[003] {Code} 'br label %return, !dbg !35'
[003] 9 {Line}
[003] {Code} '%2 = load i32, ptr %retval, align 4, !dbg !36'
[003] 9 {Line}
[003] {Code} 'ret i32 %2, !dbg !36'
[003] 3 {Line}
[003] 3 {Line}
[003] 3 {Line}
[003] {Code} 'br i1 %loadedv, label %if.then, label %if.end, !dbg !26'
[002] 1 {TypeAlias} 'INTPTR' -> '* const int'💅 EXIT STATUS 💅
llvm-debuginfo-analyzer returns 0 if the input files were parsed and printed successfully. Otherwise, it returns 1. That’s the whole mood.
😭 LIMITATIONS AND KNOWN ISSUES 😭
It literally says: See Limitations.
🔥 SEE ALSO 🔥
llvm-dwarfdump
👑 AUTHOR 👑
Maintained by the LLVM Team (https://llvm.org/).
🎀 COPYRIGHT 🎀
2003-2026, LLVM Project
mwah 💅 signing off from LLVM-DEBUGINFO-ANALYZER(1), page 23, dated 2026-10-06 — go read some debug info for me, bestie 💖
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