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cgo: document export of Go functions to C.

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R=mpimenov, rsc
CC=golang-dev, remy
https://golang.org/cl/5376082
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Rémy Oudompheng 2011-11-18 18:24:59 -05:00 committed by Russ Cox
parent 10e012c85f
commit 29e3ef88af
1 changed files with 17 additions and 0 deletions
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17
src/cmd/cgo/doc.go
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@ -87,6 +87,23 @@ by making copies of the data. In pseudo-Go definitions:
// C pointer, length to Go []byte // C pointer, length to Go []byte
func C.GoBytes(unsafe.Pointer, C.int) []byte func C.GoBytes(unsafe.Pointer, C.int) []byte
Go functions can be exported for use by C code in the following way:
//export MyFunction
func MyFunction(arg1, arg2 int, arg3 string) int64 {...}
//export MyFunction2
func MyFunction2(arg1, arg2 int, arg3 string) (int64, C.char*) {...}
They will be available in the C code as:
extern int64 MyFunction(int arg1, int arg2, GoString arg3);
extern struct MyFunction2_return MyFunction2(int arg1, int arg2, GoString arg3);
found in _cgo_export.h generated header. Functions with multiple
return values are mapped to functions returning a struct.
Not all Go types can be mapped to C types in a useful way.
Cgo transforms the input file into four output files: two Go source Cgo transforms the input file into four output files: two Go source
files, a C file for 6c (or 8c or 5c), and a C file for gcc. files, a C file for 6c (or 8c or 5c), and a C file for gcc.