[Bug c/83222] New: [ 8 regression] Inconsistent "initializer element is not constant" error

[ian at airs dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83222

            Bug ID: 83222
           Summary: [ 8 regression] Inconsistent "initializer element is
                    not constant" error
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ian at airs dot com
  Target Milestone: ---

The handling of this C program recently changed:

const char _expA = 0x42;
void __cgo_f_1_4(void) { static const double x = (double)(_expA); }

With a GCC built on October 10, 2017, I get this:

foo.c: In function ‘__cgo_f_1_4’:
foo.c:2:50: error: initializer element is not constant
 void __cgo_f_1_4(void) { static const double x = (double)(_expA); }
                                                  ^
With this morning's sources (November 29, 2017) the program compiles without
error.

Perhaps that change is OK.  But this similar program still fails:

const char _expA = 0x42;
double __cgodebug_floats[] = {
  _expA,
  1
};

foo1.c:3:3: error: initializer element is not constant
   _expA,
   ^~~~~
foo1.c:3:3: note: (near initialization for ‘__cgodebug_floats[0]’)


I think that if we are going to change the behavior for the first program, we
need to change the behavior for the second one.