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diff --git a/doc/gccgo_install.html b/doc/gccgo_install.html deleted file mode 100644 index c478a9ea2d..0000000000 --- a/doc/gccgo_install.html +++ /dev/null @@ -1,533 +0,0 @@ -<!--{ - "Title": "Setting up and using gccgo", - "Path": "/doc/install/gccgo" -}--> - -<p> -This document explains how to use gccgo, a compiler for -the Go language. The gccgo compiler is a new frontend -for GCC, the widely used GNU compiler. Although the -frontend itself is under a BSD-style license, gccgo is -normally used as part of GCC and is then covered by -the <a href="https://www.gnu.org/licenses/gpl.html">GNU General Public -License</a> (the license covers gccgo itself as part of GCC; it -does not cover code generated by gccgo). -</p> - -<p> -Note that gccgo is not the <code>gc</code> compiler; see -the <a href="/doc/install.html">Installing Go</a> instructions for that -compiler. -</p> - -<h2 id="Releases">Releases</h2> - -<p> -The simplest way to install gccgo is to install a GCC binary release -built to include Go support. GCC binary releases are available from -<a href="https://gcc.gnu.org/install/binaries.html">various -websites</a> and are typically included as part of GNU/Linux -distributions. We expect that most people who build these binaries -will include Go support. -</p> - -<p> -The GCC 4.7.1 release and all later 4.7 releases include a complete -<a href="/doc/go1.html">Go 1</a> compiler and libraries. -</p> - -<p> -Due to timing, the GCC 4.8.0 and 4.8.1 releases are close to but not -identical to Go 1.1. The GCC 4.8.2 release includes a complete Go -1.1.2 implementation. -</p> - -<p> -The GCC 4.9 releases include a complete Go 1.2 implementation. -</p> - -<p> -The GCC 5 releases include a complete implementation of the Go 1.4 -user libraries. The Go 1.4 runtime is not fully merged, but that -should not be visible to Go programs. -</p> - -<p> -The GCC 6 releases include a complete implementation of the Go 1.6.1 -user libraries. The Go 1.6 runtime is not fully merged, but that -should not be visible to Go programs. -</p> - -<p> -The GCC 7 releases include a complete implementation of the Go 1.8.1 -user libraries. As with earlier releases, the Go 1.8 runtime is not -fully merged, but that should not be visible to Go programs. -</p> - -<p> -The GCC 8 releases include a complete implementation of the Go 1.10.1 -release. The Go 1.10 runtime has now been fully merged into the GCC -development sources, and concurrent garbage collection is fully -supported. -</p> - -<p> -The GCC 9 releases include a complete implementation of the Go 1.12.2 -release. -</p> - -<h2 id="Source_code">Source code</h2> - -<p> -If you cannot use a release, or prefer to build gccgo for yourself, the -gccgo source code is accessible via Git. The GCC web site has -<a href="https://gcc.gnu.org/git.html">instructions for getting the GCC -source code</a>. The gccgo source code is included. As a convenience, a -stable version of the Go support is available in the -<code>devel/gccgo</code> branch of the main GCC code repository: -<code>git://gcc.gnu.org/git/gcc.git</code>. -This branch is periodically updated with stable Go compiler sources. -</p> - -<p> -Note that although <code>gcc.gnu.org</code> is the most convenient way -to get the source code for the Go frontend, it is not where the master -sources live. If you want to contribute changes to the Go frontend -compiler, see <a href="/doc/gccgo_contribute.html">Contributing to -gccgo</a>. -</p> - - -<h2 id="Building">Building</h2> - -<p> -Building gccgo is just like building GCC -with one or two additional options. See -the <a href="https://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 gccgo 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). If you are targeting a 64-bit x86, but sometimes want to use -the <code>-m32</code> option, then use the <code>configure</code> -option <code>--with-arch-32=i586</code>. -</p> - -<h3 id="Gold">Gold</h3> - -<p> -On x86 GNU/Linux systems the gccgo 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 the gold linker version 2.22 -or later. You can either install GNU binutils 2.22 or later, or you -can build gold yourself. -</p> - -<p> -To build gold yourself, build the GNU binutils, -using <code>--enable-gold=default</code> when you run -the <code>configure</code> script. Before building, you must install -the flex and bison packages. 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> -git clone git://sourceware.org/git/binutils-gdb.git -mkdir binutils-objdir -cd binutils-objdir -../binutils-gdb/configure --enable-gold=default --prefix=/opt/gold -make -make install -</pre> - -<p> -However you install gold, when you configure gccgo, use the -option <code>--with-ld=<var>GOLD_BINARY</var></code>. -</p> - -<h3 id="Prerequisites">Prerequisites</h3> - -<p> -A number of prerequisites are required to build GCC, as -described on -the <a href="https://gcc.gnu.org/install/prerequisites.html">gcc web -site</a>. It is important to install all the prerequisites before -running the gcc <code>configure</code> script. -The prerequisite libraries can be conveniently downloaded using the -script <code>contrib/download_prerequisites</code> in the GCC sources. - -<h3 id="Build_commands">Build commands</h3> - -<p> -Once all the prerequisites are installed, then a typical build and -install sequence would look like this (only use -the <code>--with-ld</code> option if you are using the gold linker as -described above): -</p> - -<pre> -git clone --branch devel/gccgo git://gcc.gnu.org/git/gcc.git gccgo -mkdir objdir -cd objdir -../gccgo/configure --prefix=/opt/gccgo --enable-languages=c,c++,go --with-ld=/opt/gold/bin/ld -make -make install -</pre> - -<h2 id="Using_gccgo">Using gccgo</h2> - -<p> -The gccgo compiler works like other gcc frontends. As of GCC 5 the gccgo -installation also includes a version of the <code>go</code> command, -which may be used to build Go programs as described at -<a href="https://golang.org/cmd/go">https://golang.org/cmd/go</a>. -</p> - -<p> -To compile a file without using the <code>go</code> command: -</p> - -<pre> -gccgo -c file.go -</pre> - -<p> -That produces <code>file.o</code>. To link files together to form an -executable: -</p> - -<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. There are a few ways to do this: -</p> - -<ul> -<li> -<p> -Set the <code>LD_LIBRARY_PATH</code> environment variable: -</p> - -<pre> -LD_LIBRARY_PATH=${prefix}/lib/gcc/MACHINE/VERSION -[or] -LD_LIBRARY_PATH=${prefix}/lib64/gcc/MACHINE/VERSION -export LD_LIBRARY_PATH -</pre> - -<p> -Here <code>${prefix}</code> is the <code>--prefix</code> option used -when building gccgo. For a binary install this is -normally <code>/usr</code>. Whether to use <code>lib</code> -or <code>lib64</code> depends on the target. -Typically <code>lib64</code> is correct for x86_64 systems, -and <code>lib</code> is correct for other systems. The idea is to -name the directory where <code>libgo.so</code> is found. -</p> - -</li> - -<li> -<p> -Passing a <code>-Wl,-R</code> option when you link (replace lib with -lib64 if appropriate for your system): -</p> - -<pre> -go build -gccgoflags -Wl,-R,${prefix}/lib/gcc/MACHINE/VERSION -[or] -gccgo -o file file.o -Wl,-R,${prefix}/lib/gcc/MACHINE/VERSION -</pre> -</li> - -<li> -<p> -Use the <code>-static-libgo</code> option to link statically against -the compiled packages. -</p> -</li> - -<li> -<p> -Use the <code>-static</code> option to do a fully static link (the -default for the <code>gc</code> compiler). -</p> -</li> -</ul> - -<h2 id="Options">Options</h2> - -<p> -The gccgo compiler supports all GCC options -that are language independent, notably the <code>-O</code> -and <code>-g</code> options. -</p> - -<p> -The <code>-fgo-pkgpath=PKGPATH</code> option may be used to set a -unique prefix for the package being compiled. -This option is automatically used by the go command, but you may want -to use it if you invoke gccgo directly. -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>PKGPATH</code> may be any string; a good choice for the -string is the path used to import the package. -</p> - -<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. -These options are not needed if you build with the go command. -</p> - -<h2 id="Imports">Imports</h2> - -<p> -When you compile a file that exports something, the export -information will be stored directly in the object file. -If you build with gccgo directly, rather than with the go command, -then when you import a package, you must tell gccgo how to find the -file. -</p> - -<p> -When you import the package <var>FILE</var> with gccgo, -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>lib<var>FILE</var>.so</code> -<li><code>lib<var>FILE</var>.a</code> -<li><code><var>FILE</var>.o</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 -</p> - -<pre> -objcopy -j .go_export FILE.o FILE.gox -</pre> - -<p> -The gccgo 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 -gccgo. Both options take directories to search. The -<code>-L</code> option is also passed to the linker. -</p> - -<p> -The gccgo compiler does not currently (2015-06-15) record -the file name of imported packages in the object file. You must -arrange for the imported data to be linked into the program. -Again, this is not necessary when building with the go command. -</p> - -<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="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 has only limited -knowledge about Go. 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 -and interfaces will show up as two-element structures. Go -maps and channels are always represented as C pointers to run-time -structures. -</p> - -<h2 id="C_Interoperability">C Interoperability</h2> - -<p> -When using gccgo there is limited interoperability with C, -or with C++ code compiled using <code>extern "C"</code>. -</p> - -<h3 id="Types">Types</h3> - -<p> -Basic types map directly: an <code>int32</code> in Go is -an <code>int32_t</code> in C, an <code>int64</code> is -an <code>int64_t</code>, etc. -The Go type <code>int</code> is an integer that is the same size as a -pointer, and as such corresponds to the C type <code>intptr_t</code>. -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> - -<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>): -</p> - -<pre> -struct __go_string { - const unsigned char *__data; - intptr_t __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> - -<p> -A slice in Go is a structure. The current definition is -(this is <b style="color: red;">subject to change</b>): -</p> - -<pre> -struct __go_slice { - void *__values; - intptr_t __count; - intptr_t __capacity; -}; -</pre> - -<p> -The type of a Go function is a pointer to a struct (this is -<b style="color: red;">subject to change</b>). The first field in the -struct points to the code of the function, which will be equivalent to -a pointer to a C function whose parameter types are equivalent, with -an additional trailing parameter. The trailing parameter is the -closure, and the argument to pass is a pointer to the Go function -struct. - -When a Go function returns more than one value, the C function returns -a struct. For example, these functions are roughly equivalent: -</p> - -<pre> -func GoFunction(int) (int, float64) -struct { int i; float64 f; } CFunction(int, void*) -</pre> - -<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> - -<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. -</p> - -<h3 id="Function_names">Function names</h3> - -<p> -Go code can call C functions directly using a Go extension implemented -in gccgo: a function declaration may be preceded by -<code>//extern NAME</code>. For example, here is how the C function -<code>open</code> can be declared in Go: -</p> - -<pre> -//extern open -func c_open(name *byte, mode int, perm int) int -</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>syscall</code> package): -</p> - -<pre> -var name = [4]byte{'f', 'o', 'o', 0}; -i := c_open(&name[0], syscall.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> - -<p> -Note that if the C function can block, such as in a call -to <code>read</code>, calling the C function may block the Go program. -Unless you have a clear understanding of what you are doing, all calls -between C and Go should be implemented through cgo or SWIG, as for -the <code>gc</code> compiler. -</p> - -<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 <code>go</code>. -To call the function from C you must set the name using -a GCC extension. -</p> - -<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 GCC supports automatically generating -Go declarations from C code. The facility is rather awkward, and most -users should use the <a href="/cmd/cgo">cgo</a> program with -the <code>-gccgo</code> option instead. -</p> - -<p> -Compile your C code as usual, and add the option -<code>-fdump-go-spec=<var>FILENAME</var></code>. This will create the -file <code><var>FILENAME</var></code> as a side effect of the -compilation. This file will contain Go declarations for the types, -variables and functions declared in the C code. C types that can not -be represented in Go will be recorded as comments in the Go code. The -generated file will not have a <code>package</code> declaration, but -can otherwise be compiled directly by gccgo. -</p> - -<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. -</p> |