Re: bug: "gcc -std=gnu99" passes AC_PROG_CC_C11

[Paul Eggert]

Sorry, I don't see a bug there.  "gcc -std=gnu99"
accepts ISO C11, in the sense that it passes all the
C11 tests that we have, if your version of GCC is
sufficiently new.  This is because the GCC supports
these C11 features even when running in C99 mode.

If there's some C11 feature that is missing,
a feature that it's reasonable to expect from C11
compilers, we could add that to the test, and this
will cause 'configure' to say "no" rather than "yes".
I did briefly try to think of such a feature but
came up dry.