Weird segfault

Driehoek · 10-28-2009, 06:59 PM

Hello everybody,
There is a nasty segfault in my code that keeps pestering me. The error is probably buried deeply in my beastly sized code so I won't post it and ask you to deal with it, but I just want to know when this simple code...

Code:

int* value_ptr = (int*) malloc (sizeof (int));

...can result in a segmentation fault so I can track down the error better.

My idea would be never, but still it does.
(Oh, and yes apart from 'return 0' in main, this is the last line of my code.)

Any help would be appreciated.

Output of gdb:

Code:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7b011e6 in _int_malloc () from /lib/libc.so.6

Driehoek · 10-28-2009, 07:05 PM

Upon further investigation, all calls to malloc segfault. I did something weird somewhere.

Driehoek · 10-28-2009, 07:32 PM

I'm double freeing a pointer somewhere, that must be the problem.

cas · 10-28-2009, 09:40 PM

If it supports your platform, give Valgrind a try. It can catch memory problems very early, so if you overwrite malloc()'s internal housekeeping, double free, etc, it will tell you right then and there. You don't have to wait till the problem manifests itself during a later call to malloc() leaving you to guess where the corruption happened.

Kinshara · 10-29-2009, 05:55 AM

yeah.. same like me, malloc doesn't identified in my compiler.. (I use visual C)
is there someone can explain me?

Driehoek · 10-29-2009, 08:05 AM

Thanks for advising Valgrind too me Cas. I forgot about it, I solved my problem with it.

10-28-2009, 06:59 PM	#1
Driehoek Registered User Join Date: Oct 2009 Posts: 4	Weird segfault Hello everybody, There is a nasty segfault in my code that keeps pestering me. The error is probably buried deeply in my beastly sized code so I won't post it and ask you to deal with it, but I just want to know when this simple code... Code: int* value_ptr = (int) malloc (sizeof (int)); ...can result in a segmentation fault so I can track down the error better. My idea would be never, but still it does. (Oh, and yes apart from 'return 0' in main, this is the last line of my code.) Any help would be appreciated. Output of gdb: Code: Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7b011e6 in _int_malloc () from /lib/libc.so.6 Last edited by Driehoek; 10-28-2009 at 07:11 PM. Reason: Added debuging output.*
Driehoek is offline

10-28-2009, 07:05 PM	#2
Driehoek Registered User Join Date: Oct 2009 Posts: 4	Upon further investigation, all calls to malloc segfault. I did something weird somewhere.
Driehoek is offline

10-28-2009, 07:32 PM	#3
Driehoek Registered User Join Date: Oct 2009 Posts: 4	I'm double freeing a pointer somewhere, that must be the problem.
Driehoek is offline

10-28-2009, 09:40 PM	#4
cas Registered User Join Date: Sep 2007 Posts: 372	If it supports your platform, give Valgrind a try. It can catch memory problems very early, so if you overwrite malloc()'s internal housekeeping, double free, etc, it will tell you right then and there. You don't have to wait till the problem manifests itself during a later call to malloc() leaving you to guess where the corruption happened.
cas is offline

10-29-2009, 05:55 AM	#5
Kinshara Registered User Join Date: Oct 2009 Location: Indonesia Posts: 60	yeah.. same like me, malloc doesn't identified in my compiler.. (I use visual C) is there someone can explain me?
Kinshara is offline

10-29-2009, 08:05 AM	#6
Driehoek Registered User Join Date: Oct 2009 Posts: 4	Thanks for advising Valgrind too me Cas. I forgot about it, I solved my problem with it.
Driehoek is offline

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