use of alloca and optimization under XL C on AIX 3.1

[Vic Abell]

While porting GNU C to an RS/6000 under AIX 3.1 (the GA and 3015
releases) I followed the BSD porting guide and discovered that I
could not use XL C's -O optimization when I also used the

	#pragma alloca

statement - the cc1 program got a segmentation fault.  Cc1 and the
rest of GNU C would work if I disabled optimization.  In the end I
used the alloca.c package that comes with GNU C to be able to also
use compiler optimization.

Has anyone else encountered this problem?  Was my brute-force attempt
to use the pragma correct?  (I made the pragma the first statement of
each file that used alloca() after XL C complained about its location
in the config.h header file.)

Vic Abell <abe at mace.cc.purdue.edu>