M2(1)

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version 14-20240412 · 6 versions
, in ubuntu noble

✨ M2(1) from GNU ✨

Okay bestie, this is the M2(1) page from the GNU manual, and it's all about gm2, the GNU Modula-2 Compiler 💖🦋

🌸 NAME 🌸

gm2 - The GNU Modula-2 Compiler 👑

🧚 SYNOPSIS 🧚

This one's empty in the original page, so there's nothing to see here 🙈

💅 DESCRIPTION 💅

This section is also blank in the original, so we're skipping straight to the good stuff ✨

🎀 OPTIONS 🎀

okay so for any input file, the file name suffix decides what kind of compilation happens 🔥 these are the file types gm2 supports:

  • file.mod — Modula-2 implementation or program source files 💖 if your project uses a different source extension, check out -fmod= 🫶
  • file.def — Modula-2 definition module source files 🌈 these don't get compiled on their own. In GNU Modula-2, definition modules are parsed whenever a program or implementation module needs them ✨ if your project uses a different extension, check out -fdef= 💜

You can specify more than one input file on the gm2 command line,

Now for the options, periodt 💅✨

  • -g — creates debugging info so debuggers like gdb can inspect and control the executable 🔍🦋
  • -I — sets the search path for definition and implementation modules 🗺️ for example: gm2 -g -c -I.:../../libs foo.mod. If you don't set this, the default path is the current directory followed by the right language dialect library directories 🌸
  • -fauto-init — turns on auto initialization of pointers to NIL 🧸 every time a block gets created, all the pointers declared in that scope get their addresses set to NIL 💖
  • -fbounds — turns on run time checks for subranges, array indexes, and indirection through a NIL pointer 🛡️
  • -fcase — compile time checking to see whether a CASE statement needs an ELSE clause when you didn't write one 👀
  • -fcpp — preprocesses the source with cpp -lang-asm -traditional-cpp 🧹 For further details about these options, check the cpp docs 📖 If you pass -fcpp, every definition and implementation module that gets parsed will be preprocessed by cpp 🫶
  • -fdebug-builtins — calls a real function instead of the builtin equivalent 🔎 This is super handy for debugging the parameter values going into a builtin function, since you can single step into an intrinsic function 🐾
  • -fdef= — recognizes the suffix you give as a definition module filename 🌷 The default implementation and module filename suffix is .def. If you use this option, GNU Modula-2 still falls back to that default when a requested definition module isn't found 💜
  • -fdump-system-exports — displays all inbuilt system items 🧾 This one is an internal command line option, so it's more of a behind-the-scenes thing 🙈
  • -fexceptions — turns on exception handling code 🎈 It's on by default 💅 You can turn it off with -fno-exceptions, and then no references get made to the run time exception libraries 🌙
  • -fextended-opaque — lets opaque types be implemented as any type 🦄 This is a GNU Modula-2 extension, and it needs the implementation module that defines the opaque type to be available, so it can be resolved when the module importing that opaque type gets compiled 🧩
  • -ffloatvalue — turns on run time checking to see whether a floating point number is about to go out of range 📈
  • -fgen-module-list=filename — tries to find all modules at link time and generates a module list 📜 If the filename is -, the contents aren't written and the option is only used to force linking of all module ctors 🫠 You can't use this option if -fuse-list= is enabled 🚫
  • -findex — generates code to check whether array index values are out of bounds 🔢 You can disable it with -fno-index 🙅‍♀️
  • -fiso — turns on ISO standard features 🌍 Right now this enables the ISO SYSTEM module and changes the default library search path so the ISO libraries get searched before the PIM libraries 📚 It also changes how the DIV and MOD operators behave 🧮
  • -flibs= — modifies the default library search path 🛤️ The libraries you can pick are: m2pim, m2iso, m2min, m2log and m2cor 💖 These map onto the Programming in Modula-2 base libraries, the ISO standard libraries, minimal library support, the Logitech compatible library, and Programming in Modula-2 with coroutines 🧵 You can list several, separated by commas, and the first one in the list gets precedence 👑 You don't need -flibs=m2pim or -flibs=m2iso if you also specify -fpim, -fpim2, -fpim3, -fpim4 or -fiso 🫶 Unless you're using -flibs=m2min, you should include m2pim, because it provides the base modules that all the other dialects use 🌸 The option -fno-libs=- stops the gm2 driver from touching the search and library paths 🙅‍♀️
  • -static-libgm2 — on systems that offer the m2 runtimes as both shared and static libraries, this forces the static version 🪨
  • -fm2-g — makes debugging easier for new programmers 🐣 The trade-off is that it may generate nop instructions, so you can single step precisely through all the code-related keywords 👣 For example, when a list of nested IF statements ends with several END keywords, those get mapped onto a sequence of nop instructions 🥱
  • -fm2-lower-case — shows keywords in error messages in lower case 🔤
  • -fm2-pathname= — sets the module mangled prefix name for all modules in the include paths that follow 🏷️
  • -fm2-pathnameI — for internal use only 🤫 The driver uses it to copy the user-facing -I option 🔁
  • -fm2-plugin — inserts a plugin that identifies run time errors at compile time 🕵️‍♀️ It's on by default ✅
  • -fm2-prefix= — sets the module mangled prefix name 🪄 Every exported symbol from a definition module will get that prefix 💜
  • -fm2-statistics — generates quadruple information 📊 That's the number of quadruples generated, the number of quadruples left after optimization, and the number of source lines compiled 🧮
  • -fm2-strict-type — an experimental flag that turns on the new strict type checker 🧪 ⚠️ Still experimental, so use it with caution 💀
  • -fm2-whole-program — compiles all implementation modules and the program module all at once 🏃‍♀️💨
Be careful here, bestie! You need to take care if you're compiling different dialect modules, especially with negative operands to modulus 🚨 But when you pair this option with -O3, it can deliver huge performance improvements 🚀
  • -fmod= — recognizes the suffix you give as implementation and module filenames 🌷 The default implementation and module filename suffix is .mod. If you use this option, GNU Modula-2 still falls back to that default when it needs to read an implementation module and the suffixed filename you gave doesn't exist 🫶
  • -fnil — generates code to detect data access through a NIL value pointer 🕳️ You can turn off dereference checking through a NIL pointer with -fno-nil 🙅‍♀️
  • -fpim — turns on PIM standard features 📘 Right now this enables the PIM SYSTEM module and decides which identifiers are pervasive (declared in the base module) 🌍 If you don't use any other -fpim[234] switch, division and modulus behave the way PIM4 defines them 🧮
  • -fpim2 — turns on PIM-2 standard features 📗 Right now this removes SIZE from being a pervasive identifier (declared in the base module) 🙅‍♀️ It moves SIZE into the SYSTEM module instead 📦 It also changes how the DIV and MOD operators behave 🧮
  • -fpim3 — turns on PIM-3 standard features 📙 Right now this only changes how the DIV and MOD operators behave 🧮
  • -fpim4 — turns on PIM-4 standard features 📕 Right now this only changes how the DIV and MOD operators behave 🧮
  • -fpositive-mod-floor-div — forces DIV and MOD to behave the way PIM4 defines them ✨ All modulus results come out positive, and division results get rounded to the floor 🌸
  • -fpthread — links against the pthread library 🧵 It's on by default, and you can disable it with -fno-pthread 🙅‍♀️ GNU Modula-2 uses the GCC pthread libraries to implement coroutines, so check out the SYSTEM implementation module if you want the details 🫶
  • -frange — generates code to check the assignment range, return value range, set range and constructor range 📏 You can disable range checking with -fno-range 🙅‍♀️
  • -freturn — generates code to check that functions always exit with a RETURN and don't just fall out the end 🚪 You can disable return checking with -fno-return 🙅‍♀️
  • -fruntime-modules= — takes a comma separated list that sets the run time modules and their order 🧾 These modules get initialized first, before any other modules in the application dependency 🥇 By default the list is m2iso:RTentity,m2iso:Storage,m2iso:SYSTEM,m2iso:M2RTS,m2iso:RTExceptions,m2iso:IOLink 📋 These modules only get linked into your executable if they're actually required 🧠 Adding a long list of dependent modules won't change the size of the executable, it just states the initialization order in case they're needed 🦋
  • -fscaffold-dynamic — makes sure gm2 generates a dynamic scaffold infrastructure when compiling implementation and program modules 🏗️ It's on by default 💖 Use -fno-scaffold-dynamic to turn it off, or pick -fno-scaffold-static instead 🔀
  • -fscaffold-c — generates a C source scaffold for the module you're compiling right now 🌱
  • -fscaffold-c++ — generates a C++ source scaffold for the module you're compiling right now 💜
  • -fscaffold-main — forces the generation of the main function 🎯 You don't need this if -c is omitted 🙈
  • -fscaffold-static — makes sure gm2 generates a static scaffold within the program module 🧱 The static scaffold is made of sequences of calls to all dependent module initialization and finalization procedures 📞 It's really useful for debugging and single stepping through the initialization blocks of implementation modules 👣
  • -fshared — generates a shared library from the module 🤝
  • -fsoft-check-all — turns on all run time checks 🛡️✨ This is the same as invoking GNU Modula-2 with -fnil -frange -findex -fwholevalue -fwholediv -fcase -freturn 💅
  • -fsources — displays the path to the source of each module 🗂️ You can use it at compile time to double check that the right definition module is being used 🔍
  • -fswig — generates a swig interface file 🪶
  • -funbounded-by-reference — Okay bestie, this one is a speed boost for unbounded parameters 🚀. It tries to pass non VAR unbounded parameters by reference, so the callee doesn't make its own implicit copy. GNU Modula-2 only does this if, inside the callee, the parameter is never written to, no address is calculated on the array, and it isn't passed as a VAR parameter. ngl, it's still possible to write code that breaks this optimization, so use it carefully 💅. For example, you could take the address of an array, pass both the address and the array to a procedure, read from the array inside the procedure, and write to that location through the address parameter. Chaotic 💀
Due to the dangerous nature of this option, it is not enabled when the -O option is specified. Don't go looking for it under -O 🙈
  • -fuse-list=filename — Use the file filename to set the initialization order of modules, but only if -fscaffold-static is enabled 🗂️. If -fscaffold-dynamic is enabled instead, this file is used to force linking of all module ctors 🔗. This option cannot be used if -fgen-module-list= is enabled.
  • -fwholediv — Generates code that detects whole number division by zero and modulus by zero 🧮. Bestie, that's a safety net ✨.
  • -fwholevalue — Generates code that detects whole number overflow and underflow 📈📉. No surprise numbers sneaking up on you 🫶.
  • -Wcase-enum — Gives you a warning if a CASE statement selects on an enumerated type expression and it's missing one or more CASE labels 👀. If the CASE statement has a default ELSE clause, no warning is issued, so you're covered. The -Wall option turns this flag on for you 💖.
  • -Wuninit-variable-checking — Warns you if a variable gets used before it's initialized 🫣. The checking only happens in the first basic block of each procedure. It doesn't check parameters, array types or set types, so those are on their own 🙃.
  • -Wuninit-variable-checking=all,known,cond — Same vibe of warning, but with more levels 🎚️. The checking only happens in the first basic block of each procedure if known is specified. If cond or all is specified, the checking keeps going into conditional branches of the flow graph 🌈. All checking stops when a procedure call is invoked or when the top of a loop is encountered 🛑. The -Wall option turns this flag on with -Wuninit-variable-checking=known. Heads up that -Wuninit-variable-checking=all will increase compile time ⏳.

🔗 SEE ALSO 🔗

Copyright (c) 1999-2024 Free Software Foundation, Inc. 💜

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation, with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the man page gfdl(7) 🦋.

Okay that's the whole page, bestie 🎀 It's gcc-14 energy, dated 2024-04-12, and it's M2(1) forever 💖🌈

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