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Bug#368459: backtrace.3 revised



On Sat, May 27, 2006 at 01:01:05PM -0400, pryzbyj wrote:
> Included is a revised copy of backtrace.3.
> 
> Michael:
> 
> I was tempted to use an alternate loop condition in h():
> 
>         for (sz=1; (sz&(sz-1))==0 && (sz<<=1); ) {
>                 if (NULL==(vec=realloc(vec, sz*sizeof(*vec)))) {
>                         perror("realloc");
>                         exit(EXIT_FAILURE);
>                 }
> 
>                 sz=backtrace(vec, sz);
>         }
> 
> but I anticipated that you feel this is not the place to teach people
> about the properties of powers of two.  I mention it here in case I
> was wrong :)
> 
> BTW, |expand -t4 should be useful in the future when I forget your tab
> preference.
For some reason the example program I sent hangs (forever?) when
niterations is either 2 or 10:

15017 pryzbyj   25   0  1624  396  328 R 93.9  0.3  31:54.35 bt                 

I also opened bug #368459 against libc6, since valgrind complains
about invalid reads and use of uninit values; this might just be
because backtracing does unportable things that might generally be
undefined.  If so, it is IMO still a (minor) bug, and libc6 or
valgrind should include relevant supressions or whatever is needed to
make it quiet.

Justin



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