🚀 go-pugleaf

In article <1992Aug18.143135.6259@cc.tut.fi> mn87504@cs.tut.fi (Naatula Mika) writes:

>Sometimes my program causes a segmentation fault. If I drive it with
>CVP I can find out (from calls sequence) that the error was caused by
>malloc. To be exact, malloc calls an internal(?) function named
>_searchseg() that fails. Any ideas what this function might be?
>
>(...)
>
>My program uses a lot of dynamic memory allocation, but I am quite
>sure that there is no bugs in my code. I have spent two days checking
>out the memory allocation of this program.

I'd go back and spend some more time looking.  This very much sounds like
something in your program used and errant pointer and trashed some of the
memory control blocks used by the C compiler's memory allocation routines.
The program only dies when you next try to do a malloc and the C compiler
needs to scan for free space - the corrupted internal pointers cause the
trap.

Dynamic memory problems are very subtle and hard to track.  Two days might
only be a fraction of the time necessary to locate such a bug - I know I've
spent a significantly longer time tracking down such bugs in the past.

Some things that can help is to dump debugging output for every allocation
and free operation and ensure that everything matches.  Also - there are
some libraries around (I'm not positive where - maybe someone else can
help?) that replace the standard allocation calls, and set up signature
areas around the allocated memory to help you track down the piece of code
that is munging the wrong memory.

Alternatively, if you can somehow replicate a sequence of steps that causes
the problem (not always possible), then you can scrutinize the code path
that those steps take to see if you can find an uninitialized pointer, memory
used after freeing, fencepost errors (ie: going 1 past the end of an array),
etc..

Probably not what you wanted to hear - but I think you'll probably find the
root of this problem in your code somewhere...

--
-- David
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