On Wed, Nov 01, 2017 at 10:27:54AM +0100, Karsten Hilbert wrote:
> > >> It points to a memory corruption.
> >
> > The i386/x64 architecture supports memory access breakpoints
> > and GDB, too, has support for this. You know the address which
> > gets corrupted. Thus, the following apporach could have a chance
> > to succeed:
> >
> > Put a "memory write" breakpoint on the address which gets corrupted.
> > this should stop the program each time this address is written;
> > Check then the backtrace. As the address forms part of the
> > address block prologue, it should only be accessed from
> > Python's "malloc" (and "free") implementation. Any other access
> > indicates bad behaviour.
>
> I understand. Thank you for the explanation. This may seem
> like a dumb question: the actual address that gets corrupted
> varies from run to run (it may be the same "place" in the
> code but that place gets put at a different address each
> run). Since I don't know the address of a given run, how do I
> set a break point on that address ? It seems to me I first
> need to map the "place" to its address before the SIGABRT
> happens. How do I find out out which "place" needs to be
> mapped from the output I already have ?
Or rather: I need to find out which "place" a given address
refers to, check whether the changing addresses always belong
to the same "place" between runs and _then_ map a "place" to
its address and breakpoint that address on yet another run.
It might seem
gdb> info symbol <the address>
should give me the "place".
Then
gdb> info address <the symbol>
on another run. Or even just "watch <the symbol". I'll try.
Karsten
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