[GTALUG] Ubuntu 16.04 / gcc 5.4.0 - errors generated inside system include files

[Stewart C. Russell]

I'm hitting unexpected problems building some old-ish code (UCB Logo 6,
after hearing Seymour Papert went PENUP last week). gcc seems to be
choking on its own header file, mathcalls.h:

gcc -g -O   -O0 -DUSE_OLD_TTY   -c -o coms.o coms.c
In file included from coms.c:30:0:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:100:1: error: expected
‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘extern’
 __MATHCALL_VEC (exp,, (_Mdouble_ __x));
 ^
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:100:1: error: expected
‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘extern’
 __MATHCALL_VEC (exp,, (_Mdouble_ __x));
 ^
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:100:1: error: expected
‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘extern’
 __MATHCALL_VEC (exp,, (_Mdouble_ __x));
 ^
<builtin>: recipe for target 'coms.o' failed
make: *** [coms.o] Error 1

(this on Ubuntu 16.04, gcc 5.4.0, x86_64)

I can build other code that includes math.h, the source of the
mathcalls.h inclusion. The package builds fine on a Raspberry Pi
(Raspbian, gcc 4.9.2, armv7l). The package even built on x86_64 under
Ubuntu 15.10.

Is this just Canonical mucking about with the compiler settings again?

cheers,
 Stewart