math_errhandling getting undef'ed for -std=gnu11?

[Stephan Bergmann <sbergman at redhat dot com>]

My understanding is that C11 requires <math.h> to define 
math_errhandling (as macro or identifier with external linkage), and my 
assumption is that GCC's -std=gnu11 (vs. -std=c11), while it might 
enable language extensions, would not remove from that.

However, at least with glibc-headers-2.28-26.fc29.x86_64,

> $ cat test.c
> #include <math.h>
> int main() { return math_errhandling; }

fails for

> $ gcc -m32 -O -std=gnu11 test.c
> test.c: In function ‘main’:
> test.c:2:21: error: ‘math_errhandling’ undeclared (first use in this function)
>  int main() { return math_errhandling; }
>                      ^~~~~~~~~~~~~~~~
> test.c:2:21: note: each undeclared identifier is reported only once for each function it appears in

while it succeeds for

> $ gcc -m32 -O -std=c11 test.c

What causes the difference is apparently the block

> /* Disable x87 inlines when -fpmath=sse is passed and also when we're building
>    on x86_64.  Older gcc (gcc-3.2 for example) does not define __SSE2_MATH__
>    for x86_64.  */
> #if !defined __SSE2_MATH__ && !defined __x86_64__
> # if ((!defined __NO_MATH_INLINES || defined __LIBC_INTERNAL_MATH_INLINES) \
>      && defined __OPTIMIZE__)
>
> /* The inline functions do not set errno or raise necessarily the
>    correct exceptions.  */
> #  undef math_errhandling
[...]

in /usr/include/bits/mathinline.h.

Now, my question is whether that is by design (implying that -std=gnu11 
is deliberately non-conforming here) or by accident.

(But seeing 
<https://sourceware.org/git/?p=glibc.git;a=commit;h=da75c1b180f9355a8b2b2584ecf1fcfe03f7107e> 
"Remove x86 mathinline.h" completely dropping 
sysdeps/x86/fpu/bits/mathinline.h from later glibc probably makes the 
question somewhat moot.)