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Re: -fdump-go-spec option does not handle redefinitions
On Thu, Oct 27, 2011 at 9:29 PM, Ian Lance Taylor <iant@google.com> wrote:
>> This testfile:
>>
>> #define aa 2
>> #undef aa
>> #define aa 3
>>
>> does not generate correct output with -fdump-go-spec. The result is:
>>
>> const _aa = 2
>> // undef _aa
>>
>> One would expect:
>>
>> const _aa = 2
>> // undef _aa
>> const _aa = 3
>
> Did this come up in a real situation?
Yes, it breaks libgo build on Alpha, due to the way TCGETS and friends
are defined. From bits/ioctls.h:
/* Use the definitions from the kernel header files. */
#include <asm/ioctls.h>
/* Oh well, this is necessary since the kernel data structure is
different from the user-level version. */
#undef TCGETS
#undef TCSETS
#undef TCSETSW
#undef TCSETSF
#define TCGETS _IOR ('t', 19, char[44])
#define TCSETS _IOW ('t', 20, char[44])
#define TCSETSW _IOW ('t', 21, char[44])
#define TCSETSF _IOW ('t', 22, char[44])
> The problem with your proposal is that the output would be invalid Go,
> because it would attempt to define the name _aa twice. ?However, it does
> seem plausible that in most scenarios of this type it would be more
> useful for -fdump-go-spec to generate
>
> const _aa = 3
I agree.
Thanks,
Uros.