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>,-fdebug=<ident> | Compile in debug code, code <= level, or 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>,-fversion=<ident> | Compile in version code greater than or equal to <level>, or 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. Please see the linked GCC attribute for details about an individual attribute.
| GDC Attribute | GCC Attribute |
|---|---|
| flatten | flatten |
| forceinline* | always_inline |
| noinline* | noinline |
| target | {Not sure how this relates to GCC attributes. If you know please update this wiki} |
* 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
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.
