gm2 - The GNU Modula-2 Compiler
For any given input file, the file name suffix determines what kind of
compilation is done. The following kinds of input file names are supported:
-
file.mod
- Modula-2 implementation or program source files. See the
-fmod= option if you wish to compile a project which uses a
different source file extension.
-
file.def
- Modula-2 definition module source files. Definition modules
are not compiled separately, in GNU Modula-2 definition modules are parsed
as required when program or implementation modules are compiled. See the
-fdef= option if you wish to compile a project which uses a
different source file extension.
You can specify more than one input file on the
gm2 command line,
- "-g"
- create debugging information so that debuggers such as
gdb can inspect and control executables.
- "-I"
- used to specify the search path for definition and
implementation modules. An example is: "gm2 -g -c -I.:../../libs
foo.mod". If this option is not specified then the default path is
added which consists of the current directory followed by the appropriate
language dialect library directories.
- "-fobject-path="
- used to specify the path for objects during the linking
stage. An example is: "gm2 -g -fobject-path=.:../../libs/O2
-I.:../../libs foo.mod". The combination of "-I" and
"-fobject-path=" allows projects to keep various styles of
objects separate from their source counterparts. For example it would be
possible to compile implementation modules with different levels of
optimization and with/without debugging and keep them in separate
directories. If the "-fobject-path=" option is not specified
then it is set internally by using the path as specified by the
"-I" option. If the "-I" was also not specified then
it uses the current directory. In all cases the appropriate language
dialect library directories are appended to the end of the path.
- "-fdebug-builtins"
- call a real function, rather than the builtin equivalent.
This can be useful for debugging parameter values to a builtin function as
it allows users to single step code into a real function.
- "-fdump-system-exports"
- display all inbuilt system items. This is an internal
command line option.
- "-fswig"
- generate a swig interface file.
- "-fshared"
- generate a shared library from the module.
- "-fmakeinit"
- generate the start up C++ code for the module, a file
_m2_modulename.cpp is created. This is an internal command line
option.
- "-fruntime-modules="
- specify, using a comma separated list, the runtime modules
and their order. These modules will initialized first before any other
modules in the application dependancy. By default the runtime modules list
is set to "Storage,SYSTEM,M2RTS,RTExceptions,IOLink". Note that
these modules will only be linked into your executable if they are
required. So adding a long list of dependant modules will not effect the
size of the executable it merely states the initialisation order should
they be required.
- "-fnil"
- generate code to detect accessing data through a
"NIL" value pointer.
- "-fno-nil"
- do not generate code to detect accessing data through a
"NIL" value pointer.
- "-fwholediv"
- generate code to detect whole number division by zero or
modulus by zero.
- "-fno-wholediv"
- do not generate code to detect whole number division by
zero or modulus by zero.
- "-findex"
- generate code to check whether array index values are out
of bounds.
- "-fno-index"
- do not generate code to check whether array index values
are out of bounds.
- "-frange"
- generate code to check the assignment range, return value
range set range and constructor range.
- "-fno-range"
- do not generate code to check the assignment range, return
value range set range and constructor range.
- "-freturn"
- generate code to check that functions always exit with a
"RETURN" and do not fall out at the end.
- "-fcase"
- turns on compile time checking to check whether a
"CASE" statement requires an "ELSE" clause when on was
not specified.
- "-fsoft-check-all"
- turns on all runtime checks. This is the same as invoking
GNU Modula-2 using the command options "-fnil"
"-frange" "-findex" "-fwholediv"
"-fcase" "-freturn".
- "-fauto-init"
- turns on auto initialization of pointers to NIL. Whenever a
block is created all pointers declarated within this scope will have their
addresses assigned to NIL.
- "-fno-exceptions"
- turns off all generation of exception handling code and no
references are made to the runtime exception libraries.
- "-v"
- display all calls to subsidiary programs, such as the C
preprocessor, the GNU Modula-2 linker and compiler.
- "-fm2-statistics"
- generates quadruple information: number of quadruples
generated, number of quadruples remaining after optimisation and number of
source lines compiled.
- "-fm2-whole-program"
- compile all implementation modules and program module at
once. Notice that you need to take care if you are compiling different
dialect modules (particularly with the negative operands to modulus). But
this option, when coupled together with "-O3", can deliver huge
performance improvements.
- "-fm2-g"
- improve the debugging experience for new programmers at the
expense of generating "nop" instructions if necessary to ensure
single stepping precision over all code related keywords. An example of
this is in termination of a list of nested "IF" statements where
multiple "END" keywords are mapped onto a sequence of
"nop" instructions.
- "-fm2-lower-case"
- render keywords in error messages using lower case.
- "-fmakelist"
- this option is only applicable when linking a program
module. The compiler will generate a modulename.lst file which
contains a list indicating the initialisation order of all modules which
are to be linked. The actual link does not occur. The GNU Modula-2 linker
scans all "IMPORT"s, generates a list of dependencies and
produces an ordered list for initialisation. It will probably get the
order wrong if your project has cyclic dependencies, but the .lst
file is plain text and can be modified if required. Once the .lst
file is created it can be used by the compiler to link your project via
the -fuselist option. It has no effect if the -c option is
present.
- "fno-pthread"
- do not automatically link against the pthread library. This
option is likely useful if gm2 is configured as a cross compiler
targetting embedded systems. By default GNU Modula-2 uses the GCC pthread
libraries to implement coroutines (see the SYSTEM implementation
module).
- "-fuselist"
- providing gm2 has been told to link the program
module this option uses the file modulename.lst for the
initialisation order of modules.
- "-fcpp"
- preprocess the source with cpp -lang-asm
-traditional-cpp For further details about these options see If
-fcpp is supplied then all definition modules and implementation
modules which are parsed will be preprocessed by cpp.
- "-fiso"
- turn on ISO standard features. Currently this enables the
ISO "SYSTEM" module and alters the default library search path
so that the ISO libraries are searched before the PIM libraries. It also
effects the behaviour of "DIV" and "MOD" operators.
See
- "-fpim"
- turn on PIM standard features. Currently this enables the
PIM "SYSTEM" module and determines which identifiers are
pervasive (declared in the base module). If no other -fpim[234]
switch is used then division and modulus operators behave as defined in
PIM4. See
- "-fpim2"
- turn on PIM-2 standard features. Currently this removes
"SIZE" from being a pervasive identifier (declared in the base
module). It places "SIZE" in the "SYSTEM" module. It
also effects the behaviour of "DIV" and "MOD"
operators. See
- "-fpim3"
- turn on PIM-3 standard features. Currently this only
effects the behaviour of "DIV" and "MOD" operators.
See
- "-fpim4"
- turn on PIM-4 standard features. Currently this only
effects the behaviour of "DIV" and "MOD" operators.
See
- "-fpositive-mod-floor-div"
- forces the "DIV" and "MOD" operators to
behave as defined by PIM4. All modulus results are positive and the
results from the division are rounded to the floor. See
- "-flibs="
- modifies the default library search path. The libraries
supplied are: m2pim, m2iso, m2min, m2log and m2cor. These map onto the
Programming in Modula-2 base libraries, ISO standard libraries, minimal
library support, Logitech compatible library and Programming in Modula-2
with coroutines. Multiple libraries can be specified and are comma
separated with precidence going to the first in the list. It is not
necessary to use -flibs=m2pim or -flibs=m2iso if you also specify -fpim,
-fpim2, -fpim3, -fpim4 or -fiso. Unless you are using -flibs=m2min you
should include m2pim as the they provide the base modules which all other
dialects utilize.
- "-fextended-opaque"
- allows opaque types to be implemented as any type. This is
a GNU Modula-2 extension and it requires that the implementation module
defining the opaque type is available so that it can be resolved when
compiling the module which imports the opaque type.
- "-fsources"
- displays the path to the source of each module. This option
can be used at compile time to check the correct definition module is
being used.
- "-fmodules"
- displays the path to each modules object file. This option
can only be invoked with the "-c" option. It is used to see the
location of objects when linking occurs.
- "-fdef="
- recognise the specified suffix as a definition module
filename. The default implmentation and module filename suffix is
.def. If this option is used GNU Modula-2 will still fall back to
this default if a requested definition module is not found.
- "-fmod="
- recognise the specified suffix as implementation and module
filenames. The default implmentation and module filename suffix is
.mod. If this option is used GNU Modula-2 will still fall back to
this default if it needs to read an implmentation module and the specified
suffixed filename does not exist.
- "-fxcode"
- issues all errors and warnings in the Xcode
format.
- "-fonlylink"
- only link the modula-2 application, do not compile the
program module beforehand.
- "-funbounded-by-reference"
- enable optimization of unbounded parameters by attempting
to pass non "VAR" unbounded parameters by reference. This
optimization avoids the implicit copy inside the callee procedure. GNU
Modula-2 will only allow unbounded parameters to be passed by reference
if, inside the callee procedure, they are not written to, no address is
calculated on the array and it is not passed as a "VAR"
parameter. Note that it is possible to write code to break this
optimization, therefore this option should be used carefully. For example
it would be possible to take the address of an array, pass the address and
the array to a procedure, read from the array in the procedure and write
to the location using the address parameter.
Due to the dangerous nature of this option it is not enabled when the -O
option is specified.
- "-Wverbose-unbounded"
- inform the user which non "VAR" unbounded
parameters will be passed by reference. This only produces output if the
option -funbounded-by-reference is also supplied on the command
line.
- "-Wstudents"
- checks for bad programming style. This option is aimed at
new users of Modula-2 in that it checks for situations which might cause
confusion and thus mistakes. It checks whether variables of the same name
are declared in different scopes and whether variables look like keywords.
Experienced users might find this option too aggressive.
- "-Wpedantic"
- forces the compiler to reject nested "WITH"
statements referencing the same record type. Does not allow multiple
imports of the same item from a module. It also checks that: procedure
variables are written to before being read; variables are not only written
to but read from; variables are declared and used. If the compiler
encounters a variable being read before written it will terminate with a
message. It will check that "FOR" loop indices are not used
outside the end of this loop without being reset.
- "-Wpedantic-param-names"
- procedure parameter names are checked in the definition
module against their implementation module counterpart. This is not
necessary in ISO or PIM versions of Modula-2, but it can be extremely
useful, as long as code is intentionally written in this way.
- "-Wpedantic-cast"
- warns if the ISO system function is used and if the size of
the variable is different from that of the type. This is legal in ISO
Modula-2, however it can be dangerous. Some users may prefer to use
"VAL" instead in these situations and use "CAST"
exclusively for changes in type on objects which have the same size.
- "-Wunused-variable"
- warns if a variable has been declared and it not used.
- "-Wunused-parameter"
- warns if a parameter has been declared and it not
used.
- "-Wall"
- turn on all Modula-2 warnings.
gpl(7),
gfdl(7),
fsf-funding(7),
gcc(1) and the Info
entries for
gm2 and
gcc.
Copyright (c) 1999-2021 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).