I'm pretty inexperienced using C++, but I'm trying to compile version 2.0.2 of the SBML toolbox for matlab on a 64-bit XP platform. The SBML toolbox depends upon Xerces 2.8 and libsbml 2.3.5.
I've been able to build and compile the toolbox on a 32-bit machine, and it works when I test it. However, after rebuilding it on a 64-bit machine (which is a HUGE PITA!), I get a segmentation fault when I try to read long .xml files with it.
I suspect that the issue is caused by pointer addresses issues.
The Stack Trace from the the segmentation fault starts with:
[ 0] 000000003CB3856E libsbml.dll+165230 (StringBuffer_append+000030) [ 6] 000000003CB1BFAF libsbml.dll+049071 (EventAssignment_createWith+001631) [ 12] 000000003CB1C1D7 libsbml.dll+049623 (SBML_formulaToString+000039) [ 18] 000000003CB2C154 libsbml.dll+115028 (
So I'm looking at the StringBuffer_append function in the libsbml code:
LIBSBML_EXTERN
void
StringBuffer_append (StringBuffer_t *sb, const char *s)
{
unsigned long len = strlen(s);
StringBuffer_ensureCapacity(sb, len);
strncpy(sb->buffer + sb->length, s, len + 1);
sb->length += len;
}
ensureCapacity looks like this:
LIBSBML_EXTERN
void
StringBuffer_ensureCapacity (StringBuffer_t *sb, unsigned long n)
{
unsigned long wanted = sb->length + n;
unsigned long c;
if (wanted > sb->capacity)
{
/**
* Double the total new capacity (c) until it is greater-than wanted.
* Grow StringBuffer by this amount minus the current capacity.
*/
for (c = 2 * sb->capacity; c < wanted; c *= 2) ;
StringBuffer_grow(sb, c - sb->capacity);
}
}
and StringBuffer_grow looks like this:
LIBSBML_EXTERN
void
StringBuffer_grow (StringBuffer_t *sb, unsigned long n)
{
sb->capacity += n;
sb->buffer = (char *) safe_realloc(sb->buffer, sb->capacity + 1);
}
Is it likely that the
strncpy(sb->buffer + sb->length, s, len + 1);
in StringBuffer_append is the source of my segfault?
If so, can anyone suggest a fix? I really don't know C++, and am particularly confused by pointers and memory addressing, so am likely to have no idea what you're talking about - I'll need some hand-holding.
Also, I put details of my build process online here, in case anyone else is dealing with trying to compile C++ for 64-bit systems using Microsoft Visual C++ Express Edition.
Thanks in advance!
-Ben
In response to bk1e's comment on the question - unfortunately, I need version 2.0.2 for use with the COBRA toolbox, which doesn't work with the newer version 3. So, I'm stuck with this older version for now.
I'm also hitting some walls attempting to debug - I'm building a .dll, so in addition to recompiling xerces to make sure it has the same debugging settings in MSVC++, I also need to attach to the Matlab process to do the debugging - it's a pretty big jump for my limited experience in this environment, and I haven't dug into it very far yet.
I had hoped there was some obvious syntax issue with the buffer allocation or expansion. Looks like I'm in for a few more days of pain, though.