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g77 ordering of "COMMON A, IPAD" could cause crash on i386 platforms
- From: <aspiesrule at mcleodusa dot net>
- To: <gcc at gcc dot gnu dot org>
- Date: Tue, 4 Nov 2003 01:52:43 -0000
- Subject: g77 ordering of "COMMON A, IPAD" could cause crash on i386 platforms
If "COMMON A, IPAD" was compiled by g77 without proper padding for a 486
or higher IA-32 CPU, the AC flag in EFLAGS and the AM bit in CR0 were both
set, the program was running at PL3, and the vector (interrupt gate
descriptor) for the #AC exception was not initalized, trashed, or points to
an object that cannot be executed or is garbage, the computer could do some
strange things. Point: It is best to add proper padding, not only to reap
its performance benefits, but to prevent unnecessary exceptions (or the
potential for undefined behavior) on the i386, for example.