[Bug c/72864] New: gcc.c-torture/compile/pr72802.c fails on x86_64-apple-darwin15 with -m32

["dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72864

            Bug ID: 72864
           Summary: gcc.c-torture/compile/pr72802.c fails on
                    x86_64-apple-darwin15 with -m32
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dominiq at lps dot ens.fr
                CC: amodra at gcc dot gnu.org, iains at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-apple-darwin15
            Target: x86_64-apple-darwin15
             Build: x86_64-apple-darwin15

The test gcc.c-torture/compile/pr72802.c fails on x86_64-apple-darwin15 with
-m32

Running target unix/-m32
FAIL: gcc.c-torture/compile/pr72802.c   -O0  (test for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -O1  (test for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -O2  (test for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -O2 -flto  (test for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -O2 -flto -flto-partition=none  (test
for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -O3 -fomit-frame-pointer -funroll-loops
-fpeel-loops -ftracer -finline-functions  (test for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -O3 -g  (test for excess errors)
FAIL: gcc.c-torture/compile/pr72802.c   -Os  (test for excess errors)

The error is

[book15] f90/bug% gcc-fsf-6
/opt/gcc/_clean/gcc/testsuite/gcc.c-torture/compile/pr72802.c -w -c -m32
/var/folders/8q/sh_swgz96r7f5vnn08f7fxr00000gn/T//cc30nAcT.s:152:2: error:
symbol '_a' can not be undefined in a subtraction expression
        leal    _a-L3$pb(%ebx), %eax
        ^

with all the gcc versions I have tried from 4.8 up to trunk (7.0), i.e. latent
bug.

Compiling with clang, Apple LLVM version 7.3.0 (clang-703.0.31), I get

/opt/gcc/_clean/gcc/testsuite/gcc.c-torture/compile/pr72802.c:53:5: error:
non-void function 'fn3' should return a value [-Wreturn-type]
    return;
    ^
1 error generated.