Bug 31677

(In reply to comment #0)
> Just for information, I don't really expect a fix (but please, surprise me):
> 
> Compiling cairo 1.10.0 on Solaris/sparc using GCC 3.4.6 triggers a bug in GCC:
> 
>   CC     cairo-bentley-ottmann.lo
> cairo-bentley-ottmann.c: In function `edges_compare_x_for_y_general':
> cairo-bentley-ottmann.c:425: internal compiler error: in expand_mult, at
> expmed.c:2653

Could you provide the full compiler output and the preprocessed file?

http://gcc.gnu.org/bugs/ explains how to do it (basically add "-v -save-temps"
to your CFLAGS).

This could make it possible to (try to) provide a workaround to the compiler bug.

We were aware of this bug but in the final rush to 1.10 decided it wasn't really worth pursuing internal compiler errors further, especially for gcc that old.  Having looked at it some more now, it seems that the problem stems from gcc 3.4's buggy support for the __uint128_t datatype.  The following code triggers the bug as well:


#include <stdlib.h>
#include <inttypes.h>

int
main(int argc, char **argv)
{ 
  __uint128_t a = atol(argv[1]);
  a *= a;
  return 0;
}


As a workaround, you could disable using intrinsic 128 bit arithmetic in the cairo-wideint-type-private.h header by commenting out the block following the comment "/* gcc has a non-standard name */".  The problem had been fixed in later gcc releases, but I'm told gcc 4.5 has regressed.  A more robust fix (probably a link test for the wideint code) is needed avoid future regressions.