Hahnfeld added a comment.
In https://reviews.llvm.org/D50845#1219746, @tra wrote:
> In our case the headers from a relatively old glibc and compiler errors out
> on this:
>
> /* This function is used in the `isfinite' macro. */
> __MATH_INLINE int
> __NTH (__finite (double __x))
> {
> return (__extension__
> (((((union { double __d; int __i[2]; }) {__d: __x}).__i[1]
> | 0x800fffffu) + 1) >> 31));
> }
>
>
> expanded to this:
>
> extern __inline __attribute__ ((__always_inline__)) __attribute__
> ((__gnu_inline__)) int
> __finite (double __x) throw ()
> {
> return (__extension__
> (((((union { double __d; int __i[2]; }) {__d: __x}).__i[1]
> | 0x800fffffu) + 1) >> 31));
> }
>
>
> The error:
>
> .../include/bits/mathinline.h:945:9: error: '(anonymous union at
> .../include/bits/mathinline.h:945:9)' cannot be defined in a type specifier
> (((((union { double __d; int __i[2]; }) {__d: __x}).__i[1]
> ^
> .../include/bits/mathinline.h:945:55: error: member reference base type
> 'void' is not a structure or union
> (((((union { double __d; int __i[2]; }) {__d: __x}).__i[1]
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
>
>
> Also, whatever macros we generate do not prevent headers from using x86
> inline assembly. I see quite a few inline asm code in preprocessed output.
> The headers are from libc ~2.19.
Ok, the top preprocessor condition for that function is `#ifndef __SSE2_MATH__`
- the exact same macro that was part of the motivation. Can you please test
compiling a simple C file (including `math.h`) with `-mno-sse`? My guess would
be that this is broken as well.
If yes I'm fine with reverting because I need to teach Clang to allow anonymous
unions in type specifiers to make that weird system header work with this patch.
Repository:
rL LLVM
https://reviews.llvm.org/D50845
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