RE: Segmentation fault: what's wrong with this code?

The easiest way to diagnose this might be to build OpenSSL for debug, then =
reproduce under valgrind (with memcheck, which is the default tool). Odds a=
re decent that will tell you exactly where it went wrong. Even just running=
 under gdb with debug symbols would be useful.

The usual causes of a SEGV in a free-function are an invalid pointer or pri=
or heap corruption. An invalid pointer could be already freed (though in si=
ngle-threaded programs I think glibc is generally pretty good at catching t=
his and SIGABRTs instead) or not a pointer to a heap-allocated object (e.g.=
 because someone did pointer arithmetic on it, or overwrote it with a buffe=
r overflow elsewhere, or it's just rubbish). Prior heap corruption could be=
 many things. And, of course, a non-trivial free-function would be attempti=
ng to operate on data within the object being freed, and something there co=
uld be bogus.

But using the available tooling - valgrind or even glibc's built-in malloc =
debugging - is generally faster than code inspection, if the issue is easy =
to reproduce.

--
Michael Wojcik
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