Re: [xml] Segfault in xmlDocDumpMemory with efence

[Daniel Veillard <veillard redhat com>]

On Thu, Feb 19, 2004 at 03:23:31PM -0800, Dirk Morris wrote:
> Daniel Veillard wrote:
>
> > Crash in malloc in Linux are usually due to a corrupted
> > memory allocator data structure. Use valgrind with your code it
> > offers a far more systematic check than efence,
> I believe Electric fence's malloc doesnt use fenceposts like the libc's 
> malloc, so I doubt this is the issue.
> Each allocation gets its own page surrounded by two unmapped pages, so 
> it is impossible to walk
> to any other allocated memory without hitting an unmapped page first.
>
> I can't use valgrind on this code because it doesnt support the needed 
> system calls yet.

  you have libxml2 code, gdb and see what's happening in that 
xmlBufferCreate()

xmlBufferPtr
xmlBufferCreate(void) {
    xmlBufferPtr ret;
                                                                                
    ret = (xmlBufferPtr) xmlMalloc(sizeof(xmlBuffer));
    if (ret == NULL) {
        xmlTreeErrMemory("creating buffer");
        return(NULL);
    }
    ret->use = 0;
    ret->size = xmlDefaultBufferSize;
    ret->alloc = xmlBufferAllocScheme;
    ret->content = (xmlChar *) xmlMallocAtomic(ret->size * sizeof(xmlChar));
    if (ret->content == NULL) {
        xmlTreeErrMemory("creating buffer");
        xmlFree(ret);
        return(NULL);
    }
    ret->content[0] = 0;
    return(ret);
}

 xmlDefaultBufferSize is 4096 by default. If the memory structures
are not corrupted, tell me what's happening !

Daniel


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