math.c broken on i386, when compiling with -O1 -C

# cat <<EOF >math.c
#include <math.h>
int main() {return 0;}
EOF

# gcc -C -O1 math.c

expected, no output, exit code 0, like on amd64.

Actual is exit code 1 with output:

In file included from /usr/include/math.h:472:0,
                 from math.c:1:
/usr/include/i386-linux-gnu/bits/mathinline.h: In function 'floor':
/usr/include/i386-linux-gnu/bits/mathinline.h:746:1: error: expected ':' or ')' before string constant
 __inline_mathcodeNP (floor, __x, \
 ^
/usr/include/i386-linux-gnu/bits/mathinline.h: In function 'floorf':
/usr/include/i386-linux-gnu/bits/mathinline.h:746:1: error: expected ':' or ')' before string constant
 __inline_mathcodeNP (floor, __x, \
 ^
/usr/include/i386-linux-gnu/bits/mathinline.h: In function 'floorl':
/usr/include/i386-linux-gnu/bits/mathinline.h:746:1: error: expected ':' or ')' before string constant
 __inline_mathcodeNP (floor, __x, \
 ^
/usr/include/i386-linux-gnu/bits/mathinline.h: In function 'ceil':
/usr/include/i386-linux-gnu/bits/mathinline.h:764:1: error: expected ':' or ')' before string constant
 __inline_mathcodeNP (ceil, __x, \
 ^
/usr/include/i386-linux-gnu/bits/mathinline.h: In function 'ceilf':
/usr/include/i386-linux-gnu/bits/mathinline.h:764:1: error: expected ':' or ')' before string constant
 __inline_mathcodeNP (ceil, __x, \
 ^
/usr/include/i386-linux-gnu/bits/mathinline.h: In function 'ceill':
/usr/include/i386-linux-gnu/bits/mathinline.h:764:1: error: expected ':' or ')' before string constant
 __inline_mathcodeNP (ceil, __x, \
 ^