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Re: gcc -O2 on alpha miscompiles ifupdown?



Please check with a gcc-2.95.3 prerelease compiled by Chris
(http://master.debian.org/~doko/alpha) or with the test release
currently in incoming.

Current gcc snapshots (2.97) can be found in experimental (currently in
incoming).

Jim Crilly writes:
 > > Anthony Towns (aj@azure.humbug.org.au) wrote:
 > > 
 > > > Like the subject says; if I build ifupdown (0.6.4-1) on alpha with -O2
 > > > it breaks, if I build it with -O0, it's fine. With -O2, trying to trace
 > > > what's going on with gdb doesn't seem to work (it jumps all over the
 > > > place, fairly meaninglessly).
 > > > 
 > > > In theory, ifupdown should just be a fairly normal ANSI C program. Most
 > > > of the data structures aren't too complicated, and at worse there are
 > > > a few function pointers. I think everything's fully typed, and there
 > > > shouldn't be any weird casting. There was some buggy realloc's in the
 > > > past (reallocing 4 bytes, instead of 4*sizeof(obj) bytes, mainly),
 > > > but I believe they're all gone.
 > > 
 > > I haven't looked at this (yet?), but I would guess it to be more bugs
 > > in gcc 2.95 we are using. If you look at the gcc 2.96 changelog you'll
 > > see there are quite a few bug fixes, a lot of them on Alpha. We've
 > > been plauged with bad gcc optimization on Alpha for about as long as I
 > > can remember.
 > > 
 > > If no one knows for sure, I may have time in the next couple of days
 > > to play with it and see. Chris Chimelis (chris@debian.org) is the one
 > > to talk to about gcc bugs on Alpha. I would say either don't use -O2
 > > (duh) or use a different gcc (probably not gonna happen anytime soon).
 > > 
 > > Ron
 > 
 > Just wanted to note I see a similar problem compiling the DAC960 driver in 
 > the 2.4 (2.2.X one works fine) kernel, with -O2 gcc segfaults, with -O0 it 
 > works. 
 > 
 > Sorry for not giving more information but my Alpha's at work right now and 
 > I'm not, I can send more on Monday if anyone want.



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