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 executable.
- "-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.
- "-fauto-init"
- turns on auto initialization of pointers to NIL. Whenever a block is
created all pointers declared within this scope will have their addresses
assigned to NIL.
- "-fbounds"
- turns on run time subrange, array index and indirection via
"NIL" pointer checking.
- "-fcase"
- turns on compile time checking to check whether a
"CASE" statement requires an
"ELSE" clause when on was not
specified.
- "-fcpp"
- preprocess the source with cpp -lang-asm -traditional-cpp For
further details about these options If -fcpp is supplied then all
definition modules and implementation modules which are parsed will be
prepossessed by cpp.
- "-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.
- "-fdef="
- recognize the specified suffix as a definition module filename. The
default implementation 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.
- "-fdump-system-exports"
- display all inbuilt system items. This is an internal command line
option.
- "-fexceptions"
- turn on exception handling code. By default this option is on. Exception
handling can be disabled by -fno-exceptions and no references are
made to the run time exception libraries.
- "-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.
- "-ffloatvalue"
- turns on run time checking to check whether a floating point number is
about to exceed range.
- "-fgen-module-list=filename"
- attempt to find all modules when linking and generate a module list. If
the filename is - then the contents are not written and only
used to force the linking of all module ctors. This option cannot be used
if -fuse-list= is enabled.
- "-findex"
- generate code to check whether array index values are out of bounds. Array
index checking can be disabled via -fno-index.
- "-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 behavior of
"DIV" and
"MOD" operators.
- "-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
precedence 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. The option -fno-libs=- disables the gm2 driver from
modifying the search and library paths.
- "-static-libgm2"
- On systems that provide the m2 runtimes as both shared and static
libraries, this option forces the use of the static version.
- "-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.
- "-fm2-pathname="
- specify the module mangled prefix name for all modules in the following
include paths.
- "-fm2-pathnameI"
- for internal use only: used by the driver to copy the user facing -I
option.
- "-fm2-plugin"
- insert plugin to identify run time errors at compile time (default
on).
- "-fm2-prefix="
- specify the module mangled prefix name. All exported symbols from a
definition module will have the prefix name.
- "-fm2-statistics"
- generates quadruple information: number of quadruples generated, number of
quadruples remaining after optimization and number of source lines
compiled.
- "-fm2-strict-type"
- experimental flag to turn on the new strict type checker.
- "-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.
- "-fmod="
- recognize the specified suffix as implementation and module filenames. The
default implementation 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 implementation module and the specified suffixed filename
does not exist.
- "-fnil"
- generate code to detect accessing data through a
"NIL" value pointer. Dereferencing
checking through a "NIL" pointer can be
disabled by -fno-nil.
- "-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.
- "-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
behavior of "DIV" and
"MOD" operators.
- "-fpim3"
- turn on PIM-3 standard features. Currently this only effects the behavior
of "DIV" and
"MOD" operators.
- "-fpim4"
- turn on PIM-4 standard features. Currently this only effects the behavior
of "DIV" and
"MOD" operators.
- "-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.
- "-fpthread"
- link against the pthread library. By default this option is on. It can be
disabled by -fno-pthread. GNU Modula-2 uses the GCC pthread
libraries to implement coroutines (see the SYSTEM implementation
module).
- "-frange"
- generate code to check the assignment range, return value range set range
and constructor range. Range checking can be disabled via
-fno-range.
- "-freturn"
- generate code to check that functions always exit with a
"RETURN" and do not fall out at the end.
Return checking can be disabled via -fno-return.
- "-fruntime-modules="
- specify, using a comma separated list, the run time modules and their
order. These modules will initialized first before any other modules in
the application dependency. By default the run time modules list is set to
"m2iso:RTentity,m2iso:Storage,m2iso:SYSTEM,"
"m2iso:M2RTS,m2iso:RTExceptions,m2iso:IOLink".
Note that these modules will only be linked into your executable if they
are required. Adding a long list of dependent modules will not effect the
size of the executable it merely states the initialization order should
they be required.
- "-fscaffold-dynamic"
- the option ensures that gm2 will generate a dynamic scaffold
infrastructure when compiling implementation and program modules. By
default this option is on. Use -fno-scaffold-dynamic to turn it off
or select -fno-scaffold-static.
- "-fscaffold-c"
- generate a C source scaffold for the current module being compiled.
- "-fscaffold-c++"
- generate a C++ source scaffold for the current module being compiled.
- "-fscaffold-main"
- force the generation of the main function. This is not necessary if
the -c is omitted.
- "-fscaffold-static"
- the option ensures that gm2 will generate a static scaffold within
the program module. The static scaffold consists of sequences of calls to
all dependent module initialization and finalization procedures. The
static scaffold is useful for debugging and single stepping the
initialization blocks of implementation modules.
- "-fshared"
- generate a shared library from the module.
- "-fsoft-check-all"
- turns on all run time checks. This is the same as invoking GNU Modula-2
using the command options "-fnil"
"-frange"
"-findex"
"-fwholevalue"
"-fwholediv"
"-fcase"
"-freturn".
- "-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.
- "-fswig"
- generate a swig interface file.
- "-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.
- "-fuse-list=filename"
- if -fscaffold-static is enabled then use the file filename
for the initialization order of modules. Whereas if
-fscaffold-dynamic is enabled then use this file to force linking
of all module ctors. This option cannot be used if
-fgen-module-list= is enabled.
- "-fwholediv"
- generate code to detect whole number division by zero or modulus by
zero.
- "-fwholevalue"
- generate code to detect whole number overflow and underflow.
- "-Wcase-enum"
- generate a warning if a "CASE" statement
selects on an enumerated type expression and the statement is missing one
or more "CASE" labels. No warning is
issued if the "CASE" statement has a
default "ELSE" clause. The option
-Wall will turn on this flag.
- "-Wuninit-variable-checking"
- issue a warning if a variable is used before it is initialized. The
checking only occurs in the first basic block in each procedure. It does
not check parameters, array types or set types.
- "-Wuninit-variable-checking=all,known,cond"
- issue a warning if a variable is used before it is initialized. The
checking will only occur in the first basic block in each procedure if
known is specified. If cond or all is specified then
checking continues into conditional branches of the flow graph. All
checking will stop when a procedure call is invoked or the top of a loop
is encountered. The option -Wall will turn on this flag with
-Wuninit-variable-checking=known. The
-Wuninit-variable-checking=all will increase compile time.
gpl(7), gfdl(7), fsf-funding(7),
gcc(1) and the Info entries for gm2 and gcc.
Copyright (c) 1999-2023 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).