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diff --git a/doc/gccgo_install.html b/doc/gccgo_install.html deleted file mode 100644 index 159fab7bb..000000000 --- a/doc/gccgo_install.html +++ /dev/null @@ -1,409 +0,0 @@ -<!-- Setting up and using gccgo --> - -<p> -This document explains how to use <code>gccgo</code>, a compiler for -the Go language. The <code>gccgo</code> compiler is a new frontend -for <code>gcc</code>, the widely used GNU compiler. Although the -frontend itself is under a BSD-style license, <code>gccgo</code> is -normally used as part of <code>gcc</code> and is then covered by -the <a href="http://www.gnu.org/licenses/gpl.html">GNU General Public -License</a>. -</p> - -<p> -Note that <code>gccgo</code> is not the <code>6g</code> compiler; see -the <a href="install.html">Installing Go</a> instructions for that -compiler. -</p> - -<h2 id="Source_code">Source code</h2> - -<p> -The <code>gccgo</code> source code is accessible via Subversion. The -<code>gcc</code> web site -has <a href="http://gcc.gnu.org/svn.html">instructions for getting the -<code>gcc</code> source code</a>. The <code>gccgo</code> source code -is a branch of the main <code>gcc</code> code -repository: <code>svn://gcc.gnu.org/svn/gcc/branches/gccgo</code>. -</p> - -<p> -Note that although <code>gcc.gnu.org</code> is the most convenient way -to get the source code for the compiler, that is not where the master -sources live. If you want to contribute changes to the gccgo -compiler, see <a href="gccgo_contribute.html">Contributing to -gccgo</a>. -</p> - - -<h2 id="Building">Building</h2> - -<p> -Building <code>gccgo</code> is just like building <code>gcc</code> -with one or two additional options. See -the <a href="http://gcc.gnu.org/install/">instructions on the gcc web -site</a>. When you run <code>configure</code>, add the -option <code>--enable-languages=c,c++,go</code> (along with other -languages you may want to build). If you are targeting a 32-bit x86, -then you will want to build <code>gccgo</code> to default to -supporting locked compare and exchange instructions; do this by also -using the <code>configure</code> option <code>--with-arch=i586</code> -(or a newer architecture, depending on where you need your programs to -run). -</p> - -<p> -On x86 GNU/Linux systems the <code>gccgo</code> compiler is able to -use a small discontiguous stack for goroutines. This permits programs -to run many more goroutines, since each goroutine can use a relatively -small stack. Doing this requires using a development version of -the <code>gold</code> linker. The easiest way to do this is to build -the GNU binutils, using <code>--enable-gold</code> when you run -the <code>configure</code> script, and to -use <code>--with-ld=GOLD_BINARY</code> when you -configure <code>gccgo</code>. A typical sequence would look like -this (you can replace <code>/opt/gold</code> with any directory to -which you have write access): -</p> - -<pre> -cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src login -[password is "anoncvs"] -cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src co binutils -mkdir binutils-objdir -cd binutils-objdir -../src/configure --enable-gold --prefix=/opt/gold -make -make install -</pre> - -<p> -A number of prerequisites are required to build <code>gcc</code>, as -described on the <a href="http://gcc.gnu.org/">gcc web site</a>. If -those are all available, then a typical build and install sequence -would look like this (only use the <code>--with-ld</code> option if -you built and installed the gold linker as described above): -</p> - -<pre> -svn checkout svn://gcc.gnu.org/svn/gcc/branches/gccgo gccgo -mkdir objdir -cd objdir -../gccgo/configure --enable-languages=c,c++,go --with-ld=/opt/gold/bin/ld -make -make install -</pre> - -<h2 id="Using_gccgo">Using gccgo</h2> - -<p> -The <code>gccgo</code> compiler works like other gcc frontends. - -<p> -To compile a file: - -<pre> -gccgo -c file.go -</pre> - -<p> -That produces <code>file.o</code>. To link files together to form an -executable: - -<pre> -gccgo -o file file.o -</pre> - -<p> -To run the resulting file, you will need to tell the program where to -find the compiled Go packages. This can be done either by setting -<code>LD_LIBRARY_PATH</code> in your environment: - -<pre> -LD_LIBRARY_PATH=/usr/lib/gcc/MACHINE/VERSION -</pre> - -<p> -or by passing a <code>-Wl,-R</code> option when you link: - -<pre> -gccgo -o file file.o -Wl,-R,/usr/lib/gcc/MACHINE/VERSION -</pre> - -<p> -or you can use the <code>-static-libgo</code> link-time option to link -statically against libgo, or you can do a fully static link (static -linking is the default for the <code>6l</code> Go linker). On most -systems, a static link will look something like: - -<pre> -gccgo -o file file.o -static -L /usr/lib/nptl -lgobegin -lgo -lpthread -</pre> - -<p> -You may get a warning about not creating an <code>.eh_frame_hdr</code> -section; this has nothing to do with Go, and may be ignored. In the -future the requirement of explicitly specifying -<code>-L /usr/lib/nptl -lgobegin -lgo -lpthread</code> -may be removed. - - -<h2 id="Options">Options</h2> - -<p> -The <code>gccgo</code> compiler supports all <code>gcc</code> options -that are language independent, notably the <code>-O</code> -and <code>-g</code> options. - -<p> -The <code>-fgo-prefix=PREFIX</code> option may be used to set a unique -prefix for the package being compiled. This option is intended for -use with large programs that contain many packages, in order to allow -multiple packages to use the same identifier as the package name. -The <code>PREFIX</code> may be any string; a good choice for the -string is the directory where the package will be installed. - -<p> -The <code>-fno-require-return-statement</code> option may be used to -disable the compiler error about functions missing return statements. -Note that there is no way to disable this error in <code>6g</code>. - -<p> -The <code>-I</code> and <code>-L</code> options, which are synonyms -for the compiler, may be used to set the search path for finding -imports. - - -<h2 id="Imports">Imports</h2> - -<p> -When you compile a file which exports something, the export -information will be stored directly in the object file. When -you import a package, you must tell <code>gccgo</code> how to -find the file. - -<p> -When you import the package <var>FILE</var> with <code>gccgo</code>, -it will look for the import data in the following files, and use the -first one that it finds. - -<ul> -<li><code><var>FILE</var>.gox</code> -<li><code><var>FILE</var>.o</code> -<li><code>lib<var>FILE</var>.so</code> -<li><code>lib<var>FILE</var>.a</code> -</ul> - -<p> -<code><var>FILE</var>.gox</code>, when used, will typically contain -nothing but export data. This can be generated from -<code><var>FILE</var>.o</code> via - -<pre> -objcopy -j .go_export FILE.o FILE.gox -</pre> - -<p> -The <code>gccgo</code> compiler will look in the current -directory for import files. In more complex scenarios you -may pass the <code>-I</code> or <code>-L</code> option to -<code>gccgo</code>. Both options take directories to search. The -<code>-L</code> option is also passed to the linker. - -The <code>gccgo</code> compiler does not currently (2009-11-06) record -the file name of imported packages in the object file. You must -arrange for the imported data to be linked into the program. - -<pre> -gccgo -c mypackage.go # Exports mypackage -gccgo -c main.go # Imports mypackage -gccgo -o main main.o mypackage.o # Explicitly links with mypackage.o -</pre> - -<h2 id="Unimplemented">Unimplemented</h2> - -<p> -Some Go features are not yet implemented in <code>gccgo</code>. As of -2010-08-23, the following are not implemented: - -<ul> -<li>goroutines are implemented as NPTL threads. If you can not use - the gold linker as described above, they are created with a fixed - stack size, and the number of goroutines that may be created at - one time is limited. -</ul> - -<h2 id="Debugging">Debugging</h2> - -<p> -If you use the <code>-g</code> option when you compile, you can run -<code>gdb</code> on your executable. The debugger doesn't (yet) -know anything about Go. However, you can set breakpoints, single-step, -etc. You can print variables, but they will be printed as though they -had C/C++ types. For numeric types this doesn't matter. Go strings -will show up as pointers to structures; to see the value -<code>print *stringvar</code>. In general Go strings, maps, channels -and interfaces are always represented as C pointers. - -<h2 id="C_Interoperability">C Interoperability</h2> - -<p> -When using <code>gccgo</code> there is limited interoperability with C, -or with C++ code compiled using <code>extern "C"</code>. - -<h3 id="Types">Types</h3> - -<p> -Basic types map directly: an <code>int</code> in Go is an <code>int</code> -in C, etc. Go <code>byte</code> is equivalent to C <code>unsigned char</code>. -Pointers in Go are pointers in C. A Go <code>struct</code> is the same as C -<code>struct</code> with the same fields and types. - -<p> -The Go <code>string</code> type is currently defined as a two-element -structure (this is <b style="color: red;">subject to change</b>): - -<pre> -struct __go_string { - const unsigned char *__data; - int __length; -}; -</pre> - -<p> -You can't pass arrays between C and Go. However, a pointer to an -array in Go is equivalent to a C pointer to the -equivalent of the element type. -For example, Go <code>*[10]int</code> is equivalent to C <code>int*</code>, -assuming that the C pointer does point to 10 elements. - -<p> -A slice in Go is a structure. The current definition is -(this is <b style="color: red;">subject to change</b>): - -<pre> -struct __go_slice { - void *__values; - int __count; - int __capacity; -}; -</pre> - -<p> -The type of a Go function with no receiver is equivalent to a C function -whose parameter types are equivalent. When a Go function returns more -than one value, the C function returns a struct. For example, these -functions have equivalent types: - -<pre> -func GoFunction(int) (int, float64) -struct { int i; float64 f; } CFunction(int) -</pre> - -<p> -A pointer to a Go function is equivalent to a pointer to a C function -when the functions have equivalent types. - -<p> -Go <code>interface</code>, <code>channel</code>, and <code>map</code> -types have no corresponding C type (<code>interface</code> is a -two-element struct and <code>channel</code> and <code>map</code> are -pointers to structs in C, but the structs are deliberately undocumented). C -<code>enum</code> types correspond to some integer type, but precisely -which one is difficult to predict in general; use a cast. C <code>union</code> -types have no corresponding Go type. C <code>struct</code> types containing -bitfields have no corresponding Go type. C++ <code>class</code> types have -no corresponding Go type. - -<p> -Memory allocation is completely different between C and Go, as Go uses -garbage collection. The exact guidelines in this area are undetermined, -but it is likely that it will be permitted to pass a pointer to allocated -memory from C to Go. The responsibility of eventually freeing the pointer -will remain with C side, and of course if the C side frees the pointer -while the Go side still has a copy the program will fail. When passing a -pointer from Go to C, the Go function must retain a visible copy of it in -some Go variable. Otherwise the Go garbage collector may delete the -pointer while the C function is still using it. - -<h3 id="Function_names">Function names</h3> - -<p> -Go code can call C functions directly using a Go extension implemented -in <code>gccgo</code>: a function declaration may be followed by -<code>__asm__("NAME")</code>. For example, here is how the C function -<code>open</code> can be declared in Go: - -<pre> -func c_open(name *byte, mode int, perm int) int __asm__ ("open"); -</pre> - -<p> -The C function naturally expects a nul terminated string, which in -Go is equivalent to a pointer to an array (not a slice!) of -<code>byte</code> with a terminating zero byte. So a sample call -from Go would look like (after importing the <code>os</code> package): - -<pre> -var name = [4]byte{'f', 'o', 'o', 0}; -i := c_open(&name[0], os.O_RDONLY, 0); -</pre> - -<p> -(this serves as an example only, to open a file in Go please use Go's -<code>os.Open</code> function instead). - -<p> -The name of Go functions accessed from C is subject to change. At present -the name of a Go function that does not have a receiver is -<code>prefix.package.Functionname</code>. The prefix is set by -the <code>-fgo-prefix</code> option used when the package is compiled; -if the option is not used, the default is simply <code>go</code>. -To call the function from C you must set the name using -a <code>gcc</code> extension similar to the <code>gccgo</code> -extension. - -<pre> -extern int go_function(int) __asm__ ("myprefix.mypackage.Function"); -</pre> - -<h3 id="Automatic_generation_of_Go_declarations_from_C_source_code"> -Automatic generation of Go declarations from C source code</h3> - -<p> -The Go version of <code>gcc</code> supports automatically generating -Go declarations from C code. The facility is rather awkward at present, -and a better mechanism is under development. - -<p> -Compile your C code as usual, but replace <code>-c</code> with -<code>-S -ggo</code>. The result will be an assembler file -with a <code>.s</code> extension. This assembler file will contain -comments beginning with #GO. Those comments are declarations in the Go -language for the C types, variables and functions declared in the C code. -C types which can not be represented in Go will contain the string INVALID. -Unsupported macro definitions will be recorded as <code>unknowndefine</code>, -and uses of <code>#undef</code> will be recorded as <code>undef</code>. -So it is very approximately possible to get Go code by running - -<pre> -gcc -S -ggo foo.c -grep '#GO' foo.s | grep -v INVALID | grep -v unknowndefine | grep -v undef > foo.go -</pre> - -<p> -This procedure is full of unstated caveats and restrictions and we make no -guarantee that it will not change in the future. It is more useful as a -starting point for real Go code than as a regular procedure. - -<h2 id="RTEMS_Port">RTEMS Port</h2> -<p> -The <code>gccgo</code> compiler has been ported to <a href="http://www.rtems.com/"> -<code>RTEMS</code></a>. <code>RTEMS</code> is a real-time executive -that provides a high performance environment for embedded applications -on a range of processors and embedded hardware. The current <code>gccgo</code> -port is for x86. The goal is to extend the port to most of the -<a href="http://www.rtems.org/wiki/index.php/SupportedCPUs"> -architectures supported by <code>RTEMS</code></a>. For more information on the port, -as well as instructions on how to install it, please see this -<a href="http://www.rtems.com/wiki/index.php/GCCGoRTEMS"><code>RTEMS</code> Wiki page</a>. |