Using GDC
Contents
User Documentation
Usage of GDC
Simple Compilation
Creating an executable is quite easy.
gdc main.d -o main
This will attempt to compile and link the file 'main.d' and place the output into the file 'main'. If you do not use the -o switch, then your executable will be called 'a.out'.
On a typical Unix system, you can execute the resulting program with "./main" or "./a.out". On Windows, you can run the program with "main" or "a.out".(?)
To help make a transition from DMD to GDC easier, there is a script called 'gdmd' which maps DMD's command line options to GDC. To see the available options for gdmd, type 'gdmd' or 'gdmd -help' on the command line.
Command line switches
Many of the options in GCC may also be applicable to GDC, such as optimization flags, -O1, -O2, -Os, -O3, or flags such as -c, which compiles a file, but does not link it, and will send the object file to "main.o", if you file is main.d
Compiler Options
| Switch | Description |
|---|---|
| -debuglib=<lib> | Link against a debug <lib> instead of Phobos. |
| -defaultlib=<lib> | Link against <lib> instead of Phobos. |
| -fdeps | Print information about module dependencies. |
| -fdeps=<file> | Write module dependencies to <file>. |
| -fdoc | Generate Ddoc documentation. |
| -fdoc-dir=<dir> | Write Ddoc documentation files to <dir>. |
| -fdoc-file=<file> | Write Ddoc documentation to <file>. |
| -fdoc-inc=<file> | Include a Ddoc macro <file>. |
| -fintfc | Generate D interface files, |
| -fintfc-dir=<dir> | Write D interface files to directory <dir>. |
| -fintfc-file=<file> | Write D interface file to <file>. |
| -fmake-deps | Print information about module Makefile dependencies. |
| -fmake-deps=<file> | Write Makefile dependency output to <file>. |
| -fmake-mdeps | Like -fmake-deps but ignore system modules. |
| -fmake-mdeps=<file> | Like -fmake-deps=<file> but ignore system modules. |
| -fonly=<file> | Process all modules specified on the command line, but only generate code for the module <file>. |
| -fXf=<file> | Write JSON documenation to <file>. |
| -imultilib <dir> | Set <dir> to be the multilib include subdirectory. |
| -iprefix <path> | Specify <path> as a prefix for next two options. |
| -isysroot <dir> | Set <dir> to be the system root directory. |
| -isystem <dir> | Add <dir> to the start of the system include path. |
| -I <dir> | Add <dir> to the list of the module import paths. |
| -J <dir> | Add <dir> to the list of string import paths. |
| -nophoboslib | Do not link the standard D library in the compilation. |
| -nostdinc | Do not search standard system include directories. |
| -nostdlib | Do not link the standard gcc libraries in the compilation. |
Language Options
Most of these have both positive and negative forms; the negative form of -ffoo is -fno-foo. This page lists only one of these two forms, whichever one is not the default.
| Switch | Description |
|---|---|
| -fno-assert | Generate runtime code for the assert keyword.
|
| -fno-bounds-check | Generate runtime code for checking array bounds before indexing. |
| -fno-builtin | Recognize built-in functions. |
| -fno-debug | Controls the compilation of debug code.
|
| -fdebug=<level> | Compile in debug code less than or equal to that in <level>. |
| -fdebug=<ident> | Compile in debug code identified by <ident>. |
| -fd-verbose | Print information about D language processing to stdout. |
| -fd-vtls | Print information about all variables going into thread local storage to stdout. |
| -femit-templates | Generate code for all template instantiations, not just used instantiations. |
| -fno-in | Controls the compilation of in contracts.
|
| -fno-invariants | Controls the compilation of invariant contracts.
|
| -fno-emit-moduleinfo | Controls whether or not ModuleInfo is generated for the module.
|
| -fno-out | Controls the compilation of out contracts.
|
| -fproperty | Enforce @property syntax of D code. |
| -frelease | Compile release version. Equivalent to -fno-invariants -fno-in -fno-out -fno-assert -fno-bounds-check. |
| -funittest | Controls the compilation of unittest code.
|
| -fversion=<level> | Compile in version code greater than or equal to that in <level>. |
| -fversion=<ident> | Compile in version code identified by <ident>. |
| -Wall | Enable most warning messages. |
| -Werror | Error out the compiler on warnings. |
| -Wdeprecated | Enable warning of deprecated language features. |
| -Wunknown-pragmas | Enable warning of unsupported pragmas. |
Extensions
Extended Assembler
GDC implements a GCC extension that allows inline assembler with D expression operands. It is available on nearly all targets, not just i386. The syntax differs from the C language extension in the following ways:
- Statements start with 'asm { ...', just like the regular DMD inline assembler.
- It is not necesary to put parentheses around operands.
- Instruction templates can be compile-time string constants, not just string literals. If the template is not a string literal, use parenthesis to indicate that it is not an opcode.
Unlike i386 inline assembler statements, extended assembler statements do not prevent a function from being inlined.
See the GCC manual for more information about this extension.
Example:
uint invert(uint v)
{
uint result;
version(X86)
asm{ "notl %[iov]" : [iov] "=r" result : "0" v; }
else version(PPC)
asm{ "nor %[oresult],%[iv],%[iv]" : [oresult] "=r" result : [iv] "r" v; }
return result;
}
Attributes
GDC supports a small subset of the GCC attributes. The syntax differs from the C language __attribute__ extension in the following ways:
- All attributes are recognised only through the 'gcc.attribute' module.
- The attribute, and all its arguments are comma-dellimied CTFE strings packed in a tuple.
- Nesting (brackets) for attribute arguments are optional.
| Attribute | Description |
|---|---|
| forceinline* | Inlines the function even if no optimization level is specified. |
| flatten | Inlines every call inside this function, if possible. |
| noinline* | Prevents the function from being considered for inlining. |
| target | Specify that the function is to be compiled with different target options than specified on the command line. |
* Being backend attributes, you can't enforce that these attributes actually take effect in user code (no static asserts!) - but you have some guarantee in that the backend will complain if it can't apply the attribute
Example:
import gcc.attribute;
@attribute("noinline") void foobar() { }
@attribute("target", ("sse3")) void sse3_func() { }
Known Issues
See bugzilla to see bugs that have been reported to GDC.
More bugs may be found here.
Some more known issues, taken from here:
- See DStress for known failing cases. (Again, may be irrelevant)
- Debugging information may have a few problems. For D symbol name demangling you need at least gdb 7.2.
- Some targets do not support once-only linking. A workaround is to manually control template emission. See the -femit-templates option below. For Darwin, Apple's GCC 3.x compiler supports one-only linking, but GDC does not build with those sources. There are no problems with the stock GCC 4.x on Darwin.
- Complex floating point operations may not work the same as DMD.
- Some math functions behave differently due to different implementations of the extended floating-point type.
- Volatile statements may not always do the right thing.
- Because of a problem on AIX, the linker will pull in more modules than needed.
- Some C libraries (Cygwin, MinGW, AIX) don't handle floating-point formatting and parsing in a standard way.
