static vs. shared linking

[David Stacey]

On 25/03/2015 22:11, David Stacey wrote:
> On 25/03/2015 16:59, Warren Young wrote:
>> If that makes the symptom disappear, I wonder if there’s some problem 
>> with a Cygwin *.exe owning a std::string that gets resized by a 
>> Cygwin *.dll.  If so, that probably*is*  a memory ownership 
>> coordination problem that affects Cygwin proper.
>
> In order to test your hypothesis about memory ownership, I'll create a 
> test that malloc(3)s some memory in the .exe and free(3)s it in a 
> shared library; Corinna showed that the crash was coming from an 
> abort() in free(). However, I can't believe it's that simple - you'd 
> think there would be dozens of programmes crashing for this reason.

Indeed. I created a very simple test that alloc(3)s memory in main() and 
then free(3)s it in a shared library. That works fine. So there's more 
to it than that :-(

Dave.



// crash_library.h
#ifndef CRASH_LIBRARY_H
#define CRASH_LIBRARY_H

extern void Crash(unsigned short *ptr);

#endif // CRASH_LIBRARY_H



// crash_library.cpp
#include "crash_library.h"
#include <stdlib.h>

void Crash(unsigned short *ptr)
{
   free(ptr);
}



// main.cpp
#include "crash_library.h"
#include <stdlib.h>

int main()
{
   unsigned short*ptr = (unsigned short*)malloc(sizeof(unsigned short));
   Crash(ptr);
   return 0;
}



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