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Date: Fri, 23 Sep 2011 22:06:07 +0200
From: Christian Franke <Christian DOT Franke AT t-online DOT de>
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To: cygwin AT cygwin DOT com
Subject: gcc4: libstdc++6-4.5.3-2 is probably not backwards compatible
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ddrescue segfaults in option parsing after gcc was updated from 4.3.4-4 
to 4.5.3-2.
(ddrescue package was build with g++ 4.3.4-3)

I tracked down the problem to a segfault in vector< string > destructor, 
see attached testcase.


1. Compile and run with g++ 4.3.4, use -O2 to enable inline expansion:

$ g++ -O2 -o testvector testvector.cpp

$ cygcheck -f /bin/cygstdc++-6.dll
libstdc++6-4.3.4-4

$ ./testvector
vector created (12)
vector destroyed


2. Update libstdc++ and rerun:

$ cygcheck -f /bin/cygstdc++-6.dll
libstdc++6-4.5.3-2

$ ./testvector
vector created (12)
Aborted (core dumped)


Recompiling with new g++ fixes the problem.
Old inline code is probably no longer compatible with code in new 
cygstdc++-6.dll.

-- 
Regards,
Christian Franke


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#include <cstdio>
#include <string>
#include <vector>

int main()
{
  {
    std::vector<std::string> v;
    v.resize(1);
    printf("vector created (%d)\n", (int)sizeof(v)); fflush(stdout);
  }
  printf("vector destroyed\n"); fflush(stdout);
  return 0;
}



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