Black Magic: __EXTENSIONS__

[Amos Shapira]

Hello,
 While installin GCC 1.37.1 on Iris 4D under Irix 3.3, I found that
 programs which refference sys_siglist compile and resolve this
 refference when compiled by the regular cc and not when compiled with
 GCC. When I #define __EXTENSIONS__ and include <signal.h> things work
 O.K. cc(1) doesn't define it when calling cpp (from running "cc -v").
 And it seems that cpp define this internally.

 I didn't find any mention of sys_siglist under /usr/include/*.h nor
 under /usr/include/sys/*.h. Also the only refferences in /usr/lib
 describe sys_siglist as an external symbol, none of them define it.

 What happens here?

Thanks in advance,
Amos Shapira
amoss at batata.huji.ac.il