gdb fails to build (was: Re: [PATCH v2 0/3] Remote thread name support)

[Tobias Burnus <tobias.burnus@physik.fu-berlin.de>]

Hello all,

today, I fail to build gdb using GCC 6; looking at the changes, the culprit
seems to be this patch set. (I don't know whether it caused the issue or
just revealed it.) In any case, using yesterday's GDB with yesterday's GCC
worked.

The error I see is for remove.c - using stddef.h via common-defs.h:

gcc -g -O2   -I. -I../../gdb -I../../gdb/common -I../../gdb/config -DLOCALEDIR="\"gdb/gdb-inst/share/locale\"" -DHAVE_CONFIG_H -I../../gdb/../include/opcode -I../../gdb/../opcodes/.. -I../../gdb/../readline/.. -I../../gdb/../zlib -I../bfd -I../../gdb/../bfd -I../../gdb/../include -I../libdecnumber -I../../gdb/../libdecnumber  -I../../gdb/gnulib/import -Ibuild-gnulib/import   -DTUI=1  -Ipython/python/include/python2.7 -Ipython/python/include/python2.7 -Wall -Wpointer-arith -Wno-unused -Wunused-value -Wunused-function -Wno-switch -Wno-char-subscripts -Wempty-body -Wpointer-sign -Wmissing-prototypes -Wdeclaration-after-statement -Wmissing-parameter-type -Wold-style-declaration -Wold-style-definition -Wformat-nonliteral -Werror -c -o remote.o -MT remote.o -MMD -MP -MF .deps/remote.Tpo ../../gdb/remote.c

In file included from build-gnulib/import/stdio.h:53:0,
                 from ../../gdb/common/common-defs.h:31,
                 from ../../gdb/defs.h:28,
                 from ../../gdb/remote.c:22:
build-gnulib/import/stddef.h:104:3: error: conflicting types for ‘max_align_t’
 } max_align_t;
   ^

In file included from build-gnulib/import/stddef.h:55:0,
                 from build-gnulib/import/stdio.h:53,
                 from ../../gdb/common/common-defs.h:31,
                 from ../../gdb/defs.h:28,
                 from ../../gdb/remote.c:22:
gcc/gcc-trunk/lib/gcc/x86_64-pc-linux-gnu/6.0.0/include/stddef.h:429:3: note: previous declaration of ‘max_align_t’ was here
 } max_align_t;
   ^


The definitions are as follows. GCC 6:

typedef struct {
  long long __max_align_ll __attribute__((__aligned__(__alignof__(long long))));
  long double __max_align_ld __attribute__((__aligned__(__alignof__(long double))));
} max_align_t;



GDB's build-gnulib:

typedef union
{
  char *__p _GL_STDDEF_ALIGNAS (char *);
  double __d _GL_STDDEF_ALIGNAS (double);
  long double __ld _GL_STDDEF_ALIGNAS (long double);
  long int __i _GL_STDDEF_ALIGNAS (long int);
} max_align_t;


Cheers,

Tobias