Re: Build failure, xemacs-21.1.2 on rh6-based linux-alpha-unknown

Friday, 18 June 1999

        Valdis.Kletnieks(a)vt.edu writes:

...
 *IF* you compile at -O3 or higher, *and* specify -qansialias, it
will
 make optimization decisions based on the assumption that there are no
 aliasing screws to worry about.  Otherwise, it will make pessimistic
 assumptions regarding aliasing. 
OK, thus it is likely that the proportion of AIX XEmacs versions that 
were compiled like this is extremely small.

...
 Well, the *default* xlc flags don't use aliasing.  However, this
doesn't
 mean that the code is "correct", merely that the compiler doesn't trip
 over the problme. 
The argument put forward by the egcs people is "Other compilers have
had this optimization for quite some time, so it is likely that code
that runs on multiple compilers is safe." Of course that argument only 
works if this optimization is normally enabled on those compilers. For 
AIX at least it seems it isn't.

Jan

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