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! Regards, Andy
-----Original Message----- From: Thomas Lumley [mailto:tlumley@u.washington.edu] Sent: Thursday, June 13, 2002 12:05 PM To: Liaw, Andy Cc: 'r-devel@stat.math.ethz.ch' 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 improvement.
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. -thomas
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