golang/go
Auf GitHub ansehencmd/cgo: C code with function taking pointer typedef leads to C compiler warning
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#19.832 geöffnet am 4. Apr. 2017
NeedsFixcompiler/runtimehelp wanted
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Beschreibung
Building this file gets a warning from the C compiler:
package main
// typedef struct { int i; } *PS;
// void F(PS p) {}
import "C"
func main() {
C.F(nil)
}
The warning I see is:
# command-line-arguments
cgo-gcc-prolog: In function ‘_cgo_0164fa09626e_Cfunc_F’:
cgo-gcc-prolog:37:2: warning: passing argument 1 of ‘F’ from incompatible pointer type [enabled by default]
/home/iant/foo8.go:4:7: note: expected ‘PS’ but argument is of type ‘struct <anonymous> *’
// void F(PS p) {}
^
The code generated by cgo looks like:
CGO_NO_SANITIZE_THREAD
void
_cgo_0164fa09626e_Cfunc_F(void *v)
{
struct {
struct {int i; }* p0;
} __attribute__((__packed__, __gcc_struct__)) *a = v;
_cgo_tsan_acquire();
F(a->p0);
_cgo_tsan_release();
}
The C function expects PS* but we are passing struct{int i;}*. That is, we aren't using the typedef.
Changing the Go code to use C.PS(unsafe.Pointer(nil)) also fails in the same way.