Re: build fail with message "error: redefinition of 'index' as different kind of symbol"

[Rich Felker <dalias@libc.org>]

On Wed, Jul 31, 2019 at 12:31:17AM +0900, Jeeyong Um wrote:
> Hello.
> I have a question about building musl with `_BSD_SOURCE` definition.
> 
> `src/time/__tz.c` has static variable named by `index` (line 25) and
> include `string.h` header file (line 5).
> 5  #include <string.h>
> 25 static const unsigned char *zi, *trans, *index, *types, *abbrevs,
> *abbrevs_end;
> 
> By the way, `include/string.h` includes `strings.h` when _BSD_SOURCE is
> defined (line 57).
> 56 #if defined(_BSD_SOURCE) || defined(_GNU_SOURCE)
> 57 #include <strings.h>
> 58 #endif
> 
> `include/strings.h` has a function named by `index` too (line 19).
> 13 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE) ||
> defined(_POSIX_SOURCE) \
> 14  || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE+0 < 200809L) \
> 15  || (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE+0 < 700)
> 16 int bcmp (const void *, const void *, size_t);
> 17 void bcopy (const void *, void *, size_t);
> 18 void bzero (void *, size_t);
> 19 char *index (const char *, int);
> 20 char *rindex (const char *, int);
> 21 #endif
> 
> Is it possible to build musl with _BSD_SOURCE definition in this case?
> Even though `static` modifier limits the scope of variable to the file, the
> conflict between `index` of `strings.h` and `index` of `__tz.c` seems
> unavoidable.
> Please let me know if you find any mistakes here.

The musl source files assume the default feature test macros provided
by their makefile, -D_XOPEN_SOURCE=700 which also includes POSIX base,
no extensions. Extensions by their nature bring into the namespace
things that might conflict with valid code.

If -D_BSD_SOURCE is getting into the build for musl, it likely means
you have a larger build system problem, like injecting it into CFLAGS
for every package you build. This might be making some "spurious"
problems go away, but it very well could create others. It would be
much better to fix whatever prompted you to do this to begin with. If
that's not practical, at least remove it from your build for musl.

Rich