VERILATOR(1)

📦

version 5.048 · 6 versions

💅 VERILATOR(1) 💅

User Contributed Perl Documentation

okay bestie, welcome to the VERILATOR(1) page — brought to you by User Contributed Perl Documentation. She’s giving legendary tool energy, and we’re gonna get through this together, no cap. 💖

💖 NAME 💖

Verilator — lint, compile and simulate SystemVerilog code using C++/SystemC. periodt. ✨

✨ SYNOPSIS ✨

Here’s the vibe check for how you actually call her:

verilator --help
verilator --version
verilator --binary -j 0 [options] [source_files.v]... [opt_c_files.cpp/c/cc/a/o/so]
verilator --cc [options] [source_files.v]... [opt_c_files.cpp/c/cc/a/o/so]
verilator --sc [options] [source_files.v]... [opt_c_files.cpp/c/cc/a/o/so]
verilator --lint-only -Wall [source_files.v]...

🌸 DESCRIPTION 🌸

The Verilator package converts all synthesizable, and many behavioral, Verilog and SystemVerilog designs into a C++ or SystemC model that after compiling can be executed. Lowkey iconic behavior. 👑

Real talk though: Verilator is not a traditional simulator, but a compiler. She’s built different, fr fr. 💅

For documentation see <https://verilator.org/verilator_doc.html>.

🎀 ARGUMENT SUMMARY 🎀

This is a short summary of the arguments to the verilator executable. See <https://verilator.org/guide/latest/exe_verilator.html> for the detailed descriptions of these arguments.

<file.v> — Verilog package, module, and top module filenames. These are the main characters of your file list, ngl. 🌟
<file.c/cc/cpp> — Optional C++ files to compile in. Extra C++? She said “say less,” bestie. 🫶
<file.a/o/so> — Optional C++ files to link in. Throw them in the group chat, iykyk. 🔥
+1364-1995ext+<ext> — says use Verilog 1995 when you see files with the extension <ext>. old school, but make it fashion 💅
+1364-2001ext+<ext> — use Verilog 2001 for <ext> files. glow up from 1995 ✨
+1364-2005ext+<ext> — use Verilog 2005 for <ext> files. the 2005 era said let there be more features 💖
+1800-2005ext+<ext> — use SystemVerilog 2005 for <ext> files. entering the SV era 🦋
+1800-2009ext+<ext> — use SystemVerilog 2009 for <ext> files. 2009 said hold my coffee ☕
+1800-2012ext+<ext> — use SystemVerilog 2012 for <ext> files. the 2012 vibes are immaculate 🌈
+1800-2017ext+<ext> — use SystemVerilog 2017 for <ext> files. 2017 said we're not done yet 🔥
+1800-2023ext+<ext> — use SystemVerilog 2023 for <ext> files. freshest of fresh, no cap 👑
--no-aslr — turns off address space layout randomization. just don't, bestie 💀
--no-assert — kills all assertions. they're silenced, periodt 🤫
--no-assert-case — kills those unique/unique0/priority-case assertions. bye bye 👋
--autoflush — flushes streams after every $display. everything comes out immediately, no waiting 💦
--bbox-sys — blackboxes unknown $system calls. wraps them up like a lil gift 🎁
--bbox-unsup — blackboxes unsupported language features. we don't talk about those 🙈
--binary — builds a model binary. it's giving executable energy 🏃‍♀️
--build — builds the model executable/library after Verilation. the main event after the pre-game 🎬
--build-dep-bin <filename> — overrides the build dependency Verilator binary. swap out the binary, swap out the vibe 🔄
--build-jobs <jobs> — sets parallelism for --build. more jobs = more multitasking 💪
--cc — creates C++ output. C++ bestie, we love to see it 💙
-CFLAGS <flags> — C++ compiler arguments for the makefile. pass those flags like notes in class 📝
--compiler <compiler-name> — tunes for the specified C++ compiler. tell Verilator which compiler it's dealing with 🤝
--compiler-include — includes an additional header in the precompiled one. extra header, extra sparkle ✨
--constraint-array-limit <size> — maximum array size for constraint array reduction. big arrays need limits too 🚧
--converge-limit <loops> — tunes convergence settle time. how many loops till we chill? 🌀
--coverage — enables all coverage. turned all the way up, no dimming 🔆
--coverage-expr — enables expression coverage. tracking every expression like a stalker 👀
--coverage-expr-max <value> — maximum permutations allowed for an expression. cap it, bestie 🧢
--coverage-fsm — enables FSM state/arc coverage. state machine tea is piping hot 🍵
--coverage-line — enables line coverage. every line counts, literally 📏
--coverage-max-width <width> — maximum array depth for coverage. depth limit, we're not going to the abyss 🌊
--coverage-toggle — enables toggle coverage. flip flop flippin' 🔄
--coverage-underscore — enables coverage of _signals. those sneaky underscores get tracked too 🕵️‍♀️
--coverage-user — enables SVL user coverage. user-defined coverage, you do you 💁‍♀️
-D<var>[=<value>] — sets a preprocessor define. define it like you mean it 💅
--debug — enables debugging. detective mode activated 🕵️‍♂️
--debug-check — enables debugging assertions. double-checking the debug, very meta 🔁
--no-debug-leak — stops leaking memory in --debug mode. no more leaky vibes 🚰
--debugi <level> — enables debugging at a specified level. dial the debug up to level <level> 🎚️
--debugi-<srcfile> <level> — enables debugging a source file at a level. per-file debug control, fancy 🎀
--no-decoration — disables comments and lowers the spacing level. minimalism era, clean aesthetic 🤍
--decorations <level> — sets output comment and spacing level. decoration level: <level> 💐
--default-language <lang> — default language to parse. start with <lang> as the main character 🎭
+define+<var>=<value> — sets a preprocessor define. plus sign energy, but it's a define ➕
--diagnostics-sarif — enables SARIF diagnostics output. bougie diagnostic format, we love 📊
--diagnostics-sarif-output <filename> — sets the SARIF diagnostics output file. write it to <filename> 📁
--dpi-hdr-only — only produces the DPI header file. header only, no extras 💁
--dump-<srcfile> — enables dumping everything in the source file. dump it all, no filter 🗑️
--dump-defines — shows preprocessor defines with -E. spill the defines, bestie 🫖
--dump-dfg — enables dumping DfgGraphs to .dot files. graph dump, aesthetic .dot files 🕸️
--dump-dfg-patterns — enables dumping Dfg pattern statistics. stats on patterns, very analytical 📈
--dump-graph — enables dumping V3Graphs to .dot files. more graphs, more .dot 🌐
--dump-inputs — enables dumping preprocessed input files. input files, dumped 📥
--dump-tree — enables dumping Ast .tree files. tree files, branching out 🌳
--dump-tree-addrids — uses short identifiers instead of addresses. short IDs, cute and concise 🆔
--dump-tree-dot — enables dumping Ast .tree.dot debug files. debug files with .dot extension, periodt 🔴
--dump-tree-json — enables dumping Ast .tree.json files and a .tree.meta.json file. JSON everywhere, we love data 📦
--dumpi-<srcfile> <level> — enables dumping everything in a source file at a level. source file dump, level <level> 🎚️
--dumpi-dfg <level> — enables dumping DfgGraphs to .dot files at level. DFG dump level <level> 📉
--dumpi-graph <level> — enables dumping V3Graphs to .dot files at level. graph dump level <level> 📊
--dumpi-tree <level> — enables dumping Ast .tree files at level. tree dump level <level> 🌲
--dumpi-tree-json <level> — enables dumping Ast .tree.json files at level. JSON tree dump level <level> 🗂️
-E — preprocesses but does not compile. just the pre-game, no actual game 🏈
--emit-accessors — emits getter and setter methods for the model top class. getters and setters, so polite 🎩
--error-limit <value> — aborts after this number of errors. too many errors? we out ✌️
--exe — links to create an executable. executable time, let's go 🏃
--expand-limit <value> — sets the expand optimization limit. limit the expansion, contain the chaos 🧩
-F <file> — parses arguments from a file, relatively. relative file parsing, fancy 📄
-f <file> — parses arguments from a file. just read the file, bestie 📖
-FI <file> — forces inclusion of a file. force include, no take-backs 💥
--flatten — forces inlining of all modules, tasks and functions. flatten it all like a pancake 🥞
--func-recursion-depth <value> — maximum recursive constant function depth. recursion depth limit, don't get lost 🌀
--future0 <option> — ignores an option for compatibility. future vibes, but ignore it 🤖
--future1 <option> — ignores an option with an argument for compatibility. future with argument, still ignored 🛸
-fno-<optimization> — disables an internal optimization stage. turn off that optimization, we don't need it 🚫
-G<name>=<value> — overwrites a top-level parameter. change the parameter, change the game 🎮
--gate-stmts <value> — tunes gate optimizer depth. gate optimizer depth tuning, very technical 💅
--gdb — runs Verilator under GDB interactively. GDB interactive mode, debug like a pro 🐛
--gdbbt — runs Verilator under GDB for a backtrace. backtrace via GDB, get that stack trace 📚
--generate-key — creates a random key for --protect-key. random key generation, secure vibes 🔑
--get-supported <feature> — gets if a feature is supported. is <feature> supported? let's find out 🔍
--getenv <var> — gets an environment variable with defaults. env var with defaults, convenient 🌍
--help — shows this help. the classic help flag, always there for you 🆘
--hierarchical — enables hierarchical Verilation. hierarchical mode, organized and chic 🏛️
--hierarchical-block <block> — internal use only for --hierarchical. internal only, don't touch 🚧
--hierarchical-child <block> — internal use only for --hierarchical. also internal, also don't touch 🙅‍♀️
--hierarchical-params-file <name> — internal option that specifies parameters file for hier blocks. internal params file, keep it moving 📁
--hierarchical-threads <threads> — number of threads for hierarchical scheduling. threads for scheduling, multitasking queen 👑
-I<dir> — directory to search for includes. include directory, search here 🔎
--if-depth <value> — tunes the IFDEPTH warning. tune that IFDEPTH warning, just right 🎛️
+incdir+<dir> — directory to search for includes. another include directory, plus sign style ➕
--inline-cfuncs <value> — inlines CFuncs with <=value nodes (0=off). inline those CFuncs, 0 means off 🚫
--inline-cfuncs-product <value> — inlines CFuncs if size*calls <= value. inline if size times calls is small enough 🧮
--inline-mult <value> — tunes module inlining. module inlining tuning, get it just right 🎚️
--instr-count-dpi <value> — assumed dynamic instruction count of DPI imports. assumed instruction count for DPI, just a guess 🤔
-j <jobs> — parallelism for --build-jobs/--verilate-jobs. set the jobs, parallel processing 💪
--no-json-edit-nums — don't dump editNum in .tree.json files. no edit numbers, keep it clean 🧼
--no-json-ids — don't use short identifiers instead of addresses/paths in .tree.json. no short IDs in JSON, use the full thing 📛
--json-only — creates JSON parser output (.tree.json and .meta.json). JSON only, no compiler output 📦
--json-only-meta-output <filename> — sets .tree.meta.json output filename. meta JSON output filename set to <filename> 📝
--json-only-output <filename> — sets .tree.json output filename. JSON output filename set to <filename> 📄
--l2-name <value> — Verilog scope name of the top module. top module scope name, so important 🏷️
--language <lang> — default language standard to parse. default language standard, <lang> is the vibe 🌐
-LDFLAGS <flags> — linker pre-object arguments for the makefile. linker flags, pre-object, very specific 🔗
-libmap — specifies a library mapping file. library mapping file, map it out 🗺️
--lib-create <name> — creates a DPI library. DPI library creation, <name> it 📚
+libext+<ext>+[ext]... — extensions for finding modules. library extensions for finding modules, plus signs everywhere ➕
+librescan — ignored for compatibility. literally ignored, just there for compatibility 🚫
--lint-only — lints but does not make output. lint only, no output, just vibes 🧹
--localize-max-size <value> — tunes the localize optimization variable size. localize optimization size tuning, get it right 🎯
--main — generates a C++ main() file. generate that main file, C++ style 🎬
--main-top-name — specifies the top name passed to the Verilated model in the generated C++ main. top name for the generated main, name it right 🏷️
--make <build-tool> — generates scripts for the specified build tool. generate scripts for <build-tool>, build tool time 🛠️
-MAKEFLAGS <flags> — arguments to pass to make during --build. make flags for the build, pass them along 📤
--max-num-width <value> — maximum number width (default: 64K). max number width, default is 64K 📏
--Mdir <directory> — name of the output object directory. output directory name, <directory> is the spot 📂
--MMD — creates .d dependency files. create those .d files, dependency style 📄
--mod-prefix <topname> — name to prepend to lower classes. prefix for lower classes, <topname> prepended 🏷️
--MP — creates phony dependency targets. phony targets, fake but useful 👻
+notimingchecks — ignored. literally ignored, periodt 🚫
-o <executable> — name of the final executable. name the executable <executable> 🏃‍♀️
-O0 — disables optimizations. zero optimizations, raw and unfiltered 🧊
-O1 — default optimizations. default optimizations, the standard vibe 🎛️
-O2 — stronger optimizations. stronger optimizations, level up 💪
-O3 — high-performance optimizations. high-performance, maxed out 🔥
-O<optimization-letter> — selectable optimizations. pick your optimization letter, choose your fighter 🎮
--output-groups <numfiles> — groups .cpp files into larger ones. group those .cpp files, bigger is better 📦
--output-split <statements> — splits .cpp files into pieces. split .cpp files into pieces, portion control 🍰
--output-split-cfuncs <statements> — splits model functions. split model functions, divide and conquer ✂️
--output-split-ctrace <statements> — splits tracing functions. split tracing functions, trace it out 🔍
-P — disables line numbers and blanks with -E. no line numbers or blanks, minimalist 💅
--pins-bv <bits> — specifies types for top-level ports. pin types for top-level ports, <bits> style 📌
--pins-inout-enables — specifies that __en and __out signals be created for inouts. create __en and __out for inouts, fancy pins 📍
--pins-sc-biguint — specifies types for top-level ports. SC biguint pin types, specific 🎯
--pins-sc-uint — specifies types for top-level ports. SC uint pin types, very typed 🔢
--pins-sc-uint-bool — specifies types for top-level ports. SC uint bool pin types, boolean energy 🔘
--pins-uint8 — specifies types for top-level ports. uint8 pin types, small but mighty 🐜
--no-pins64 — don't use uint64_t's for 33-64 bit sigs. no 64-bit pins, keep it smaller 🚫
--pipe-filter <command> — filters all input through a script. pipe filter through <command>, script it up 🎬
--prefix <topname> — name of top-level class. top-level class name, <topname> 🏷️
--preproc-comments — includes preprocessor comments in the output with -E. preprocessor comments in output, with -E 💬
--preproc-defines — includes preprocessor defines in the output with -E. preprocessor defines in output, with -E 📝
--preproc-resolve — includes all found modules in the output with -E. all found modules in output, with -E 🧩
--preproc-token-limit — maximum tokens on a line allowed by the preprocessor. max tokens per line, preprocessor limit 🚦
--private — debugging; see docs. private debugging thing, see docs for the tea 🕵️
--prof-c — compiles C++ code with profiling. profile that C++ code, see where time goes ⏱️
--prof-cfuncs — names functions for profiling. name functions for profiling, label them 🏷️
--prof-exec — enables generating an execution profile for a gantt chart. exec profile for gantt chart, fancy chart 📊
--prof-pgo — enables generating profiling data for PGO. PGO profiling data, optimize later 📈
--protect-ids — hashes identifier names for obscurity. hash those identifiers, keep them secret 🔒
--protect-key <key> — key for symbol protection. protection key, <key> 🔑
--protect-lib <name> — creates a DPI protected library. protected DPI library, <name> it 🛡️
--public — marks signals as public; see docs. public signals, see docs 📢
--public-depth <level> — marks public to a specified module depth. public up to depth <level>, deep public 🌊
--public-flat-rw — marks all variables, etc as public_flat_rw. mark all as public_flat_rw, flat and public 🏷️
--public-ignore — ignores all public comment markings. ignore public markings, we don't see them 🙈
--public-params — marks all parameters as public_flat. mark all params as public_flat, flat public 🌐
-pvalue+<name>=<value> — overwrites a toplevel parameter. overwrite the toplevel parameter, <name>=<value> style 🔄
--quiet — minimizes additional printing. quiet mode, shhh 🤫
--quiet-build — doesn't print build progress. no build progress printing, silent build 🤐
--quiet-exit — shhh, don't print the command when it fails 🙈
--quiet-stats — no statistics printing, we're keeping it lowkey
--relative-includes — resolve includes relative to the current file
--reloop-limit <value> — minimum iterations for forming loops
--replication-limit <value> — replication concatenation limit (default: 8k)
--report-unoptflat — extra diagnostics for UNOPTFLAT, the messiest of warnings
--rr — run Verilator and record everything with rr
--runtime-debug — enable model runtime debugging
--savable — enable model save-restore
--sc — create SystemC output
--sched-zero-delay — specify #0 delay support
--no-skip-identical — disable skipping identical output
--stats — create that statistics file 📊
--stats-vars — provide statistics on variables
--no-std — prevent loading standard files
--no-std-package — prevent parsing the standard package
--no-std-waiver — prevent parsing standard lint waivers
--no-stop-fail — do not call $stop when an assertion fails
-sv — enable SystemVerilog parsing ✨
+systemverilogext+<ext> — synonym for +1800-2023ext+<ext>
--threads <threads> — enable multithreading
--threads-dpi <mode> — enable multithreaded DPI
--threads-max-mtasks <mtasks> — tune the maximum mtask partitioning
--timescale <timescale> — sets the default timescale
--timescale-override <timescale> — overrides all timescales, no exceptions 💅
--timing — enable timing support
--no-timing — disable timing support
--top <topname> — alias of --top-module
--top-module <topname> — name of the top-level input module
--trace — enable VCD waveform creation
--trace-coverage — enable tracing of coverage
--trace-depth <levels> — depth of tracing
--trace-fst — enable FST waveform creation
--trace-max-array <depth> — maximum array depth for tracing
--trace-max-width <width> — maximum bit width for tracing
--trace-params — enable tracing of parameters
--trace-saif — enable SAIF file creation
--trace-structs — enable tracing structure names
--no-trace-top — do not emit traces for signals in the top module generated by verilator
--trace-underscore — enable tracing of _signals
--trace-vcd — enable VCD waveform creation
-U<var> — undefine preprocessor define
--no-unlimited-stack — don't disable the stack size limit
--unroll-count <loops> — tune maximum loop iterations
--unroll-limit <loops> — maximum loop iterations before assuming an infinite loop 😵
--unroll-stmts <stmts> — tune maximum loop body size
--unused-regexp <regexp> — tune UNUSED lint signals
-V — verbose version and config
-v <filename> — Verilog library
--valgrind — run Verilator under valgrind
--no-verilate — skip Verilation and just compile previously Verilated code
--verilate-jobs — job threads for the Verilation stage
+verilog1995ext+<ext> — synonym for +1364-1995ext+<ext>
+verilog2001ext+<ext> — synonym for +1364-2001ext+<ext>
--version — show program version and exits
--vpi — enable VPI compiles
--waiver-multiline — create multiline --match for waivers
--waiver-output <filename> — create a waiver file based on linter warnings
-Wall — enable all style warnings, we love a thorough queen 👑
-Werror-<message> — convert warnings to errors
-Wfuture-<message> — disable unknown message warnings
-Wno-<message> — disable a warning
-Wno-context — disable source context on warnings
-Wno-fatal — disable fatal exit on warnings
-Wno-lint — disable all lint warnings
-Wno-style — disable all style warnings
-work <libname> — set config library for the following files
-Wpedantic — warn on compliance-test issues
-Wwarn-<message> — enable a specified warning message
-Wwarn-lint — enable lint warning message
-Wwarn-style — enable style warning message
--x-assign <mode> — assign non-initial Xs to this value
--x-initial <mode> — assign initial Xs to this value
--x-initial-edge — enable initial X->0 and X->1 edge triggers
-y <dir> — directory to search for modules

okay so now we're talking about the simulation runtime side of things — the args for the final Verilated simulation runtime models, bestie. this is just a lil summary; the detailed description of these arguments lives over at <https://verilator.org/guide/latest/exe_verilator.html> 🫶

+verilator+coverage+file+<filename> — set coverage output filename
+verilator+debug — enable debugging
+verilator+debugi+<value> — enable debugging at a level
+verilator+error+limit+<value> — set error limit
+verilator+help — show help
+verilator+noassert — disable assert checking
+verilator+prof+exec+file+<filename> — set execution profile filename
+verilator+prof+exec+start+<value> — set execution profile starting point
+verilator+prof+exec+window+<value> — set execution profile duration
+verilator+prof+vlt+file+<filename> — set PGO profile filename
+verilator+quiet — minimize additional printing
+verilator+rand+reset+<value> — set random reset technique
+verilator+seed+<value> — set random seed
+verilator+solver+file+<filename> — set random solver log filename
+verilator+V — show verbose version and config
+verilator+version — show version and exit
+verilator+wno+unsatconstr+<value> — disable constraint warnings

🌈 DISTRIBUTION 🌈

the latest version is right there at <https://verilator.org> — go get her 💖

Copyright 2003-2026 by Wilson Snyder. This program is free software; you can redistribute it and/or modify the Verilator internals under the terms of either the GNU Lesser General Public License Version 3 or the Perl Artistic License Version 2.0.

All Verilog and C++/SystemC code quoted within this documentation file are released as Creative Commons Public Domain (CC0). Many example files and test files are likewise released under CC0 into effectively the Public Domain as described in the files themselves.

👀 SEE ALSO 👀

verilator_coverage, verilator_gantt, verilator_profcfunc, make,
"verilator --help" which is the source for this document (periodt, that's the origin story)
and <https://verilator.org/verilator_doc.html> for the detailed documentation

okay bestie, that's the whole vibe — happy Verilating, go slay your simulation 🦋💅

this page came to you courtesy of perl v5.40.1 and is dated 2026-04-29 — iconic, timeless, no cap ✨

📦 where this page comes from

ubuntu stonking: verilator 5.048-1 · Artistic-2.0 OR LGPL-3.0-only
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-02: a language model's rewrite of the original, under its terms