On Tuesday, June 14, 2016 at 3:22:54 PM UTC-7, Ian Lance Taylor wrote:
>
> On Tue, Jun 14, 2016 at 3:15 PM, Dragos Harabor <dh...@harabor.com
> <javascript:>> wrote:
> > Is the following code supposed to work? Not sure whether I'm doing
> something
> > wrong or cgo just doesn't support this style of #defines. I reduced it
> down
> > to a simple test case, but the actual problem I ran into came from some
> 3rd
> > party .h files that unfortunately I have no control over.
> >
> > package main
> >
> > /*
> > #include <stdio.h>
> >
> > #define VERSION_A "1.2.3"
> > #define VERSION_B VERSION_A
> >
> > void f() {
> > printf("VERSION_A: %s, VERSION_B: %s\n", VERSION_A, VERSION_B);
> > }
> > */
> > import "C"
> >
> > import "fmt"
> >
> > func main() {
> > C.f()
> >
> > fmt.Println("VERSION_A:", C.VERSION_A)
> >
> > // This does not compile
> > fmt.Println("VERSION_B:", C.VERSION_B)
> > }
> >
> >
> >
> > The error I get:
> >
> > % go run cgodefine.go
> > # command-line-arguments
> >
> /tmp/go-build088092139/command-line-arguments/_obj/_cgo_main.o:(.data.rel+0x0):
>
>
> > undefined reference to `VERSION_A'
> > collect2: error: ld returned 1 exit status
>
> cgo unfortunately does not do a great job with macros. This is a bug.
> The workaround is to write code like
>
> /*
> #include "hdr.h"
>
> const char *versiona = VERSION_A;
> */
> import "C"
>
> func F() {
> fmt.Println(C.GoString(C.versiona))
> }
>
> Ian
>
Thank you Ian.
Are there any plans to fix it? This seems like a simple case, though I
realize macros can be a lot more complicated.
Unfortunately I cannot write code as your example above. What I'm really
after is the go tool cgo -godefs form to generate some Go structs out of
some C header files that I will then use to make IOCTL calls to a hardware
driver. The cgo tool in my case will just be used as a Go code generator.
Maybe I'm abusing it, but it seems to work except for quirks like the above
**_Cvar_VERSION_B*
Any link to the issue tracking this? I'd like to subscribe to it for
updates.
Thanks.
Dragos
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