[R] help debugging segfaults
Thu, 13 Jun 2002 12:48:09 -0400
OK, so I linked my code against libefence and then run my test code under
gdb. It still finishes without reporting any problem. (This is with
Calloc() and Free(), instead of S_alloc().) Can anyone tell me what to do
or look for next? I'll be eternally grateful!
> -----Original Message-----
> From: Thomas Lumley [mailto:email@example.com]
> Sent: Thursday, June 13, 2002 12:05 PM
> To: Liaw, Andy
> Cc: 'firstname.lastname@example.org'
> Subject: RE: [R] help debugging segfaults
> On Thu, 13 Jun 2002, Liaw, Andy wrote:
> > Everyone suggested using some malloc debugger (such as
> Electric Fence). All
> > I did was following half of what BDR suggested below, i.e.,
> changing all the
> > S_alloc() calls to Calloc() and Free(). I didn't get to
> try efence, and the
> > problem seems to have disappeared!
> No, the *symptoms* have disappeared. This is not necessarily an
> > As I read it from the R-exts manual, the difference between
> S_alloc and
> > Calloc is that S_alloc takes memory from the heap, whereas
> Calloc takes
> > memory addtional to the heap. So can anyone explain what's
> going on? It's
> > still kind of mysterious to me...
> It looked as if your code was writing to/reading from memory
> that didn't
> belong to it. What happens then depends on who the memory
> does belong to,
> and what they are doing with it. There's no guarantee that
> just because it
> doesn't crash today that it won't in the future, or worse,
> start giving
> subtly wrong answers.
> A segmentation fault is a good thing in this context -- it's
> a sign that
> the operating system has protected you from the consequences of your
> actions by killing the program.
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