cmd/cgo: document command line options

Also remove incorrect statement that cgo does not support
gccgo.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13511043

diff --git a/src/cmd/cgo/doc.go b/src/cmd/cgo/doc.go
index 63737d4c2b028d9e1c240e9f83f887b445052c82..b3e11e4c031c0cb060cf051f05066db7cbf08227 100644 (file)
--- a/src/cmd/cgo/doc.go
+++ b/src/cmd/cgo/doc.go
@@ -7,7 +7,7 @@
 Cgo enables the creation of Go packages that call C code.
 
 Usage:
-       go tool cgo [compiler options] file.go
+       go tool cgo [cgo options] [-- compiler options] file.go
 
 The compiler options are passed through uninterpreted when
 invoking gcc to compile the C parts of the package.
@@ -158,7 +158,44 @@ The standard package construction rules of the go command
 automate the process of using cgo.  See $GOROOT/misc/cgo/stdio
 and $GOROOT/misc/cgo/gmp for examples.
 
-Cgo does not yet work with gccgo.
+Cgo options are passed automatically by go build.
+The following options are available when running cgo directly:
+
+       -dynimport file
+               Write list of symbols imported by file. Write to
+               -dynout argument or to standard output. Used by go
+               build when building a cgo package.
+       -dynout file
+               Write -dynimport output to file.
+       -dynlinker
+               Write dynamic linker as part of -dynimport output.
+       -godefs
+               Write out input file in Go syntax replacing C package
+               names with real values. Used to generate files in the
+               syscall package when bootstrapping a new target.
+       -cdefs
+               Like -godefs, but write file in C syntax.
+               Used to generate files in the runtime package when
+               bootstrapping a new target.
+       -objdir directory
+               Put all generated files in directory.
+       -gccgo
+               Generate output for the gccgo compiler rather than the
+               gc compiler.
+       -gccgoprefix prefix
+               The -fgo-prefix option to be used with gccgo.
+       -gccgopkgpath path
+               The -fgo-pkgpath option to be used with gccgo.
+       -import_runtime_cgo
+               If set (which it is by default) import runtime/cgo in
+               generated output.
+       -import_syscall
+               If set (which it is by default) import syscall in
+               generated output.
+       -debug-define
+               Debugging option. Print #defines.
+       -debug-gcc
+               Debugging option. Trace C compiler execution and output.
 
 See "C? Go? Cgo!" for an introduction to using cgo:
 http://golang.org/doc/articles/c_go_cgo.html