Ubuntu Manpage: gm2 - The GNU Modula-2 Compiler

Provided by: gm2-11-alpha-linux-gnu_11.4.0-9ubuntu1cross1_amd64

NAME

       gm2 - The GNU Modula-2 Compiler

SYNOPSIS

DESCRIPTION

OPTIONS

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.

ENVIRONMENT

COPYRIGHT