[GDB][PR gdb/20457] Fix builds broken by proc-service changes.

[Matthew Wahab]

Hello,

GLIBC BZ#20311 introduced a change to install proc_service.h so that gdb
didn't have to use the version it embeds in gdb_proc_service.h. The
embedded version is guarded by HAVE_PROC_SERVICE_H and
gdb_proc_service.h has a number other of includes and definitions, all
of which are uncondional except for an include for gregset.h. This is
only included if HAVE_PROC_SERIVCE_H is not defined.

This causes a build failure when cross compiling gdb with the latest
glibc because type definitions in gregset are used independently of
HAVE_PROC_SERIVCE_H. In particular, they are used in gdb_proc_service.h
when PRFPREGSET_T_BROKEN is set.

The error messages on the failure are
----
binutils-gdb/gdb/gdb_proc_service.h:173:9: error: ‘gdb_fpregset_t’ does
not name a type; did you mean ‘elf_fpregset_t’?
  typedef gdb_fpregset_t gdb_prfpregset_t;
          ^~~~~~~~~~~~~~
          elf_fpregset_t

binutils-gdb/gdb/gdb_proc_service.h:173:9: error: ‘gdb_fpregset_t’ does
not name a type; did you mean ‘elf_fpregset_t’?
  typedef gdb_fpregset_t gdb_prfpregset_t;
          ^~~~~~~~~~~~~~
          elf_fpregset_t

binutils-gdb/gdb/proc-service.c:218:15: error: ‘gdb_prfpregset_t’ does
not name a type; did you mean ‘gdb_fpregset_t’?
          const gdb_prfpregset_t *fpregset)
                ^~~~~~~~~~~~~~~~
                gdb_fpregset_t
----

This patch moves the include for gregset.h to before the code guarded by
HAVE_PROC_SERIVCE_H, so that it is always included. This is enough to
fix the build.

The macro PRFPREGSET_T_BROKEN is set by the configure script which uses
AC_TRY_RUN to test the sizeof (prfregset_t) and is always set for
cross-compiled builds. It's probably better to do the test using
AC_CHECK_SIZEOF, so that cross-compiled build get the correct value.
I'll send a follow-up patch to do that.

Tested by building gdb for target and host aarch64-none-linux-gnu
against previous and current glibc and by cross-compiling for
aarch64-none-linux-gnu with new glibc on an x86_64-pc-linux-gnu host.

Is this ok?
Matthew

2016-08-12  Matthew Wahab  <matthew.wahab@arm.com>

	PR gdb/20457
	* gdb_proc_service.h: Add an include of gregset.h
         [!HAVE_PROC_SERVICE_H]: Remove the include of gregset.h.
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