<<On Mon, 15 Nov 1999 18:01:45 +0100, Pierre Beyssac <[EMAIL PROTECTED]> said:
> Maybe I can at least commit the addition of "volatile" to the source
> code. That will work around that particular bug until egcs is
> fixed...
It's not a compiler bug, it's a source code bug.
The C Language specifies that pointers to distinct types can be
assumed, under certain conditions, never to alias one another. (This
might actually be a C99 feature as opposed to C89.)
Recent values of GCC make use of this obscure language feature to
improve optimization. Essentially, the optimizer can assume that
stores through a pointer of type `foo *' will never modify any local
variable which is not of type `foo' (and thus those values can remain
cached in registers).
If, rather than casting pointers, the code used a union (containing
one u_int16_t and one array[2] of u_int8_t), the compiler would have
enough information to know about the aliases.
-GAWollman
--
Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same
[EMAIL PROTECTED] | O Siem / The fires of freedom
Opinions not those of| Dance in the burning flame
MIT, LCS, CRS, or NSA| - Susan Aglukark and Chad Irschick
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