[Bug analyzer/102779] New: gcc.dg/analyzer/capacity-1.c etc.FAIL

["ro at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102779

            Bug ID: 102779
           Summary: gcc.dg/analyzer/capacity-1.c etc.FAIL
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: ro at gcc dot gnu.org
  Target Milestone: ---
            Target: *-*-solaris2.11, powerpc-ibm-aix7.2.3.0,
                    hppa*-hp-hpux11.11, avr-unknown-none

gcc.dg/analyzer/capacity-1.c and gcc.dg/analyzer/capacity-3.c have been FAILing
on several targets, apparently for the same reason:

FAIL: gcc.dg/analyzer/capacity-1.c (test for excess errors)

Excess errors:
/vol/gcc/src/hg/master/local/gcc/testsuite/gcc.dg/analyzer/capacity-1.c:56:13:
warning: implicit declaration of function 'alloca'
[-Wimplicit-function-declaration]
/vol/gcc/src/hg/master/local/gcc/testsuite/gcc.dg/analyzer/capacity-1.c:56:13:
warning: incompatible implicit declaration of built-in function 'alloca'
[-Wbuiltin-declaration-mismatch]

FAIL: gcc.dg/analyzer/capacity-3.c (test for excess errors)

Excess errors:
/vol/gcc/src/hg/master/local/gcc/testsuite/gcc.dg/analyzer/capacity-3.c:7:13:
warning: implicit declaration of function 'alloca'
[-Wimplicit-function-declaration]
/vol/gcc/src/hg/master/local/gcc/testsuite/gcc.dg/analyzer/capacity-3.c:7:13:
warning: incompatible implicit declaration of built-in function 'alloca'
[-Wbuiltin-declaration-mismatch]

Unlike Linux, regular system headers don't implicitly declare alloca.  E.g. on
Solaris one needs to include <alloca.h>.  I wonder how best to fix this: just
use __builtin_alloca directly like some tests do, or have

#define alloca __builtin_alloca

like gcc.dg/analyzer/pr93355-localealias.c.