[Bug libstdc++/88740] New: [7/8/9 Regression] libstdc++ tests no longer print assertion failure messages

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88740

            Bug ID: 88740
           Summary: [7/8/9 Regression] libstdc++ tests no longer print
                    assertion failure messages
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

r241069 redefined the VERIFY macro so that instead of using assert it does:

#define VERIFY(fn)                                                      \
  do                                                                    \
  {                                                                     \
    if (! (fn))                                                         \
      {                                                                 \
        __builtin_printf("%s:%d: %s: Assertion '%s' failed.\n",         \
                         __FILE__, __LINE__, __PRETTY_FUNCTION__, #fn); \
        __builtin_abort();                                              \
      }                                                                 \
  } while (false)


Unlike assert, this prints to stdout not stderr.

Due to some unidentified issue in dejagnu (or expect or tcl or something else)
unflushed output sent to stdout does not get captured by dejagnu and written to
the test logs on recent versions of Fedora (and maybe other distros).

This means that testsuite failures don't show the reason for failure, just an
unhelpful:

spawn [open ...]
FAIL: 27_io/filesystem/operations/remove.cc execution test

The expected result is:

spawn [open ...]
/home/jwakely/src/gcc/libstdc++-v3/testsuite/27_io/filesystem/operations/remove.cc:38:
void test01(): Assertion '!ec' failed.
FAIL: 27_io/filesystem/operations/remove.cc execution test


The missing output can be fixed by including <cstdio> in testsuite_hooks.h and
then either changing __builtin_printf(...) to __builtin_fprintf(stderr, ...) or
alternatively adding a call to fflush(stdout) before the __builtin_abort().