[tor-bugs] #33290 [Core Tor/Tor]: Add diagnostics for confusing corruption issue #32564 in ewma

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#33290: Add diagnostics for confusing corruption issue #32564 in ewma
----------------------------------+------------------------------------
 Reporter:  nickm                 |          Owner:  nickm
     Type:  defect                |         Status:  needs_revision
 Priority:  Medium                |      Milestone:  Tor: 0.4.3.x-final
Component:  Core Tor/Tor          |        Version:  Tor: 0.4.1.6
 Severity:  Normal                |     Resolution:
 Keywords:  043-should backport?  |  Actual Points:  .1
Parent ID:  #32564                |         Points:
 Reviewer:  dgoulet               |        Sponsor:
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Comment (by dgoulet):

 Quick C test I did. With `objdump -d` you'll notice it is not there.
 Compile with `gcc -O2`:

 {{{
 #include <stdio.h>
 #include <stdlib.h>

 struct a {
   int val;
 };

 int main(int argc, char **argv)
 {
   struct a *A = malloc(sizeof(struct a));

   A->val = 0xCAFE;
   fprintf(stderr, "a: %d\n", A->val);

   A->val = 0xDEAD;
   free(A);

   return 0;
 }

 }}}

 With `gcc` without anything, you will find `CAFE` and `DEAD` but with
 `-O2`, it is optimized out.

 I've confirmed it by compiling your PR and looking at the disassemble
 code.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33290#comment:5>
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