Provided by: gdc-7_7.5.0-6ubuntu2_amd64 
NAME
gdc - A GCC-based compiler for the D language
SYNOPSIS
gdc [-c|-S] [-g] [-pg]
[-Olevel] [-Wwarn...]
[-Idir...] [-Ldir...]
[-foption...] [-mmachine-option...]
[-o outfile] [@file] infile...
Only the most useful options are listed here; see below for the remainder.
DESCRIPTION
The gdc command is a frontend to gcc and supports many of the same options. This manual
only documents the options specific to gdc.
OPTIONS
Input and Output files
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.d
D source files.
file.dd
Ddoc source files.
file.di
D interface files.
You can specify more than one input file on the gdc command line, in which case they will
all be compiled. If you specify a "-o file" option, all the input files will be compiled
together, producing a single output file, named file. This is allowed even when using
"-S" or "-c".
A D interface file contains only what an import of the module needs, rather than the whole
implementation of that module. They can be created by gdc from a D source file by using
the "-fintfc" option. When the compiler resolves an import declaration, it searches for
matching .di files first, then for .d.
A Ddoc source file contains code in the D macro processor language. It is primarily
designed for use in producing user documentation from embedded comments, with a slight
affinity towards HTML generation. If a .d source file starts with the string "Ddoc" then
it is treated as general purpose documentation, not as a D source file.
Runtime Options
These options affect the runtime behavior of programs compiled with gdc.
-fall-instantiations
Generate code for all template instantiations. The default template emission strategy
is to not generate code for declarations that were either instantiated speculatively,
such as from "__traits(compiles, ...)", or that come from an imported module not being
compiled.
-fno-assert
Turn off code generation for "assert" contracts.
-fno-bounds-check
Turns off array bounds checking for all functions, which can improve performance for
code that uses array extensively. Note that this can result in unpredictable behavior
if the code in question actually does violate array bounds constraints. It is safe to
use this option if you are sure that your code will never throw a "RangeError".
-fbounds-check=value
An alternative to -fbounds-check that allows more control as to where bounds checking
is turned on or off. The following values are supported:
on Turns on array bounds checking for all functions.
safeonly
Turns on array bounds checking only for @safe functions.
off Turns off array bounds checking completely.
-fno-builtin
Don't recognize built-in functions that do not begin with __builtin_ as prefix. By
default, the compiler will recognize when a function in the "core.stdc" package is a
built-in function.
-fdebug
-fdebug=value
Turn on compilation of conditional "debug" code into the program. The -fdebug option
itself sets the debug level to 1, while -fdebug= enables "debug" code that are
identified by any of the following values:
level
Sets the debug level to level, any "debug" code <= level is compiled into the
program.
ident
Turns on compilation of any "debug" code identified by ident.
-fno-invariants
Turns off code generation for class "invariant" contracts.
-fno-moduleinfo
Turns off generation of the "ModuleInfo" and related functions that would become
unreferenced without it, which may allow linking to programs not written in D.
Functions that will not be generated include module constructor and destructors
("static this" and "static ~this"), "unittest" code, and "DSO" registry functions for
dynamically linked code.
-fonly=filename
Tells the compiler to parse and run semantic analysis on all modules on the command
line, but only generate code for the module specified by filename.
-fno-postconditions
Turns off code generation for postcondition "out" contracts.
-fno-preconditions
Turns off code generation for precondition "in" contracts.
-frelease
Turns on compiling in release mode, which means not emitting runtime checks for
contracts and asserts. Array bounds checking is not done for @system and @trusted
functions, and assertion failures are undefined behaviour.
This is equivalent to compiling with the following options:
gdc -fno-assert -fbounds-check=safe -fno-invariants \
-fno-postconditions -fno-preconditions -fno-switch-errors
-fno-switch-errors
This option controls what code should be generated when no case is matched in a "final
switch" statement. The default run time behavior is that a "SwitchError" will be
thrown. Turning off -fswitch-errors means that instead the execution of the program
is immediately halted.
-funittest
Turns on compilation of "unittest" code, and turns on the "version(unittest)"
identifier. This implies -fassert.
-fversion=value
Turns on compilation of conditional "version" code into the program identified by any
of the following values:
level
Sets the version level to level, any "version" code >= level is compiled into the
program.
ident
Turns on compilation of "version" code identified by ident.
Options for Directory Search
These options specify directories to search for files, libraries, and other parts of the
compiler:
-Idir
Specify a directory to use when searching for imported modules at compile time.
Multiple -I options can be used, and the paths are searched in the same order.
-Jdir
Specify a directory to use when searching for files in string imports at compile time.
This switch is required in order to use "import(file)" expressions. Multiple -J
options can be used, and the paths are searched in the same order.
-Ldir
When linking, specify a library search directory, as with gcc.
-Bdir
This option specifies where to find the executables, libraries, source files, and data
files of the compiler itself, as with gcc.
-fmodule-filepath=module=spec
This option manipulates file paths of imported modules, such that if an imported
module matches all or the leftmost part of module, the file path in spec is used as
the location to search for D sources. This is used when the source file path and
names are not the same as the package and module hierachy. Consider the following
examples:
gdc test.d -fmodule-filepath=A.B=foo.d -fmodule-filepath=C=bar
This will tell the compiler to search in all import paths for the source file foo.d
when importing A.B, and the directory bar/ when importing C, as annotated in the
following D code:
module test;
import A.B; // Matches A.B, searches for foo.d
import C.D.E; // Matches C, searches for bar/D/E.d
import A.B.C; // No match, searches for A/B/C.d
-imultilib dir
Use dir as a subdirectory of the gcc directory containing target-specific D sources
and interfaces.
-iprefix prefix
Specify prefix as the prefix for the gcc directory containing target-specific D
sources and interfaces. If the prefix represents a directory, you should include the
final '/'.
-nostdinc
Do not search the standard system directories for D source and interface files. Only
the directories that have been specified with -I options (and the directory of the
current file, if appropriate) are searched.
Code Generation
In addition to the many gcc options controlling code generation, gdc has several options
specific to itself.
-M Output the module dependencies of all source files being compiled in a format suitable
for make. The compiler outputs one make rule containing the object file name for that
source file, a colon, and the names of all imported files.
-MM Like -M but does not mention imported modules from the D standard library package
directories.
-MF file
When used with -M or -MM, specifies a file to write the dependencies to. When used
with the driver options -MD or -MMD, -MF overrides the default dependency output file.
-MG This option is for compatibility with gcc, and is ignored by the compiler.
-MP Outputs a phony target for each dependency other than the modules being compiled,
causing each to depend on nothing.
-MT target
Change the target of the rule emitted by dependency generation to be exactly the
string you specify. If you want multiple targets, you can specify them as a single
argument to -MT, or use multiple -MT options.
-MQ target
Same as -MT, but it quotes any characters which are special to make.
-MD This option is equivalent to -M -MF file. The driver determines file based on the
name of the input file, removes any directory components and suffix, and applies a
.deps suffix.
-MMD
Like -MD but does not mention imported modules from the D standard library package
directories.
-X Output information describing the contents of all source files being compiled in JSON
format to a file. The driver determines file based on the name of the input file,
removes any directory components and suffix, and applies a .json suffix.
-Xf file
Same as -X, but writes all JSON contents to the specified file.
-fdeps
Dump module dependencies of all source files being compiled in a machine readable
format. Suitable for any build tool that needs to track source file dependencies for
incremental builds.
-fdeps=file
Same as -fdeps, but writes dependencies to the specified file.
-fdoc
Generates "Ddoc" documentation and writes to a file. The compiler determines file
based on the name of the input file, removes any directory components and suffix, and
applies a .html suffix.
-fdoc-dir=dir
Same as -fdoc, but writes documentation to dir directory. This option can be used
with -fdoc-file=file to independently set the output file and directory path.
-fdoc-file=file
Same as -fdoc, but writes documentation to file. This option can be used with
-fdoc-dir=dir to independently set the output file and directory path.
-fdoc-inc=file
Specify file as a Ddoc macro file to be read. Multiple -fdoc-inc options can be used,
and files are read and processed in the same order.
-fintfc
Generates D interface files for all modules being compiled. The compiler determines
the output file based on the name of the input file, removes any directory components
and suffix, and applies the .di suffix.
-fintfc-dir=dir
Same as -fintfc, but writes interface files to dir directory. This option can be used
with -fintfc-file=file to independently set the output file and directory path.
-fintfc-file=filename
Same as -fintfc but writes interface files to file. This option can be used with
-fintfc-dir=dir to independently set the output file and directory path.
Warnings
Warnings are diagnostic messages that report constructions that are not inherently
erroneous but that are risky or suggest there is likely to be a bug in the program.
Unless -Werror is specified, they do not prevent compilation of the program.
-Wall
Turns on all warnings messages. Warnings are not a defined part of the D language,
and all constructs for which this may generate a warning message are legal code.
-Wcast-result
Warn about casts that will produce a null or zero result. Currently this is only done
for casting between an imaginary and non-imaginary data type, or casting between a D
and C++ class.
-Wno-deprecated
Do not warn about usage of deprecated features and symbols with "deprecated"
attributes.
-Werror
Turns all warnings into errors.
-Wspeculative
Report on all error messages from speculative compiles, such as "__traits(compiles,
...)". This option does not report messages as warnings, and these messages therefore
never become errors when the -Werror option is also used.
-Wtemplates
Warn when a template instantiation is encountered. Some coding rules disallow
templates, and this may be used to enforce that rule.
-Wunknown-pragmas
Warn when a "pragma()" is encountered that is not understood by gdc. This differs
from -fignore-unknown-pragmas where a pragma that is part of the D language, but not
implemented by the compiler, will not get reported.
-fignore-unknown-pragmas
Turns off errors for unsupported pragmas.
-fmax-errors=n
Limits the maximum number of error messages to n, at which point gdc bails out rather
than attempting to continue processing the source code. If n is 0 (the default),
there is no limit on the number of error messages produced.
-fproperty
Enforces the @property syntax in D.
-fsyntax-only
Check the code for syntax errors, but do not actually compile it. This only
suppresses the generation of the object code, and can be used in conjunction with
-fdoc or -fintfc options.
-ftransition=id
Report additional information about D language changes identified by id. The
following values are supported:
all List information on all language changes.
checkimports
Give deprecation messages about -ftransition=import anomalies.
complex
List all usages of complex or imaginary types.
dip1000
Implements <http://wiki.dlang.org/DIP1000> (experimental).
dip25
Implements <http://wiki.dlang.org/DIP25> (experimental).
field
List all non-mutable fields which occupy an object instance.
import
Tells the compiler to revert to using an old lookup behavior for resolving
unqualified symbol names, where this was done in a single pass, ignoring any
protection attributes. The default name lookup strategy is to use two passes, the
first ignoring imported declarations, and the second only looking at imports. The
protection ("private", "package", "protected") of symbols is also enforced to
resolve any conflicts between private and public symbols.
nogc
List all hidden GC allocations.
tls List all variables going into thread local storage.
Options for Linking
These options come into play when the compiler links object files into an executable
output file. They are meaningless if the compiler is not doing a link step.
-defaultlib libname
Specify the library to use instead of libphobos when linking. Options specifying the
linkage of libphobos, such as -static-libphobos or -shared-libphobos, are ignored.
-debuglib
Specify the debug library to use instead of libphobos when linking. This option has
no effect unless the -g option was also given on the command line. Options specifying
the linkage of libphobos, such as -static-libphobos or -shared-libphobos, are ignored.
-nophoboslib
Do not use the Phobos or D runtime library when linking. Options specifying the
linkage of libphobos, such as -static-libphobos or -shared-libphobos, are ignored.
The standard system libraries are used normally, unless -nostdlib or -nodefaultlibs is
used.
-shared-libphobos
On systems that provide libgphobos and libgdruntime as a shared and a static library,
this option forces the use of the shared version. If no shared version was built when
the compiler was configured, this option has no effect.
-static-libphobos
On systems that provide libgphobos and libgdruntime as a shared and a static library,
this option forces the use of the static version. If no static version was built when
the compiler was configured, this option has no effect.
Developer Options
This section describes command-line options that are primarily of interest to developers
or language tooling.
-fdump-d-original
Dump the front-end AST after after parsing and running semantic on the source program.
Only really useful for debugging the compiler itself.
-v Dump information about the compiler language processing stages as the source program
is being compiled. This includes listing all modules that are processed through the
"parse", "semantic", "semantic2", and "semantic3" stages; all "import" modules and
their file paths; and all "function" bodies that are being compiled.
ENVIRONMENT
In addition to the many gcc environment variables that control its operation, gdc has a
few environment variables specific to itself.
D_IMPORT_PATH
The value of D_IMPORT_PATH is a list of directories separated by a special character,
much like PATH, in which to look for imports. The special character,
"PATH_SEPARATOR", is target-dependent and determined at GCC build time. For Microsoft
Windows-based targets it is a semicolon, and for almost all other targets it is a
colon.
DDOCFILE
If DDOCFILE is set, it specifies a text file of macro definitions to be read and used
by the Ddoc generator. This overrides any macros defined in other .ddoc files.
SEE ALSO
gpl(7), gfdl(7), fsf-funding(7), gcc(1) and the Info entries for gdc and gcc.
COPYRIGHT
Copyright (c) 2011-2017 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, the Front-Cover Texts being (a) (see
below), and with the Back-Cover Texts being (b) (see below). A copy of the license is
included in the man page gfdl(7).
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.