thanks for all the help, since the problem looked so weired at first I will describe what went wrong here. Maybe it´ll be useful for someone else someday:
Indeed the problem lay at some other point in the program.
I had a structure which itself contained pointers used as starting
points for a dynamical arrays.
I had two dynamical arrays (let´s say p1 and p2) of that structure. I
did allocate the memory (p1= new ...; p2=new ...) for those but with one
of them I forgot allocating the memory for the dyn. ar.s within the structure (p2[int2].px=new...). Sth. like p1[int1]=p2[int2] then corrupted the memory.
Thanks again,
Tobias
lrtaylor@xxxxxxxxxx wrote:
Have you tried looking at a stack trace to see where your program is actually crashing? With the core file, you can even look at the value of variables, etc. Whenever I get a segmentation fault, the first thing I do is look at the stack trace to see where it happened.
If you've never looked at a stack trace before, then you should probably take a look at the manual for GDB. They have a section on examining the stack. You'll also need to make sure that your programs are generating a core file when they crash. RedHat seems to have turned this off by default, but you can reenable it in the current shell using the ulimit command:
ulimit -c unlimited
Otherwise, I concur with what another poster said - you've probably corrupted memory before ever getting to this point, and this is just bringing the problem out. I would go over your code with a fine-toothed comb and look for any problems with pointers.
Good luck, Lyle
-----Original Message----- From: gcc-help-owner@xxxxxxxxxxx [mailto:gcc-help-owner@xxxxxxxxxxx]On Behalf Of Tobias Kretz Sent: Tuesday, January 13, 2004 3:32 AM To: gcc-help@xxxxxxxxxxx Subject: segmentation fault when allocating memory with new or malloc
Hi,
allocating memory with one of these lines:
pl=(list*)malloc((v)*sizeof(list)); or list*pl; pl=new list[v];
causes the program to be terminated by a segmentation fault.
v is an integer that equals e.g. 7 in my test runs (thus far from throwing a bad_alloc)
and list is trivially: struct list{ int x; int y; double d; };
Replacing the variable v by a constant value does not improve the situation.
Also:
cout << "A\n";
try {pl=new list[v];}
catch(bad_alloc) {cerr<< "not enough memory\n";}
cout << "B\n";
results in the output:
A
Segmentation fault
Additionally weird is that omitting the memory allocation
makes the program run further. Yet it crashes with a seg fault.
when trying to set up an outfile stream:
bmpofstream image("floor.bmp",xmax,ymax);
later in the program. The rest of the program contains datastructures for which I allcoate some 100kB memory (with new).
I use g++, gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)
Regards, ToK
-- ---------------------------------------------------------------------- Tobias Kretz | Lotharstr. 1, Building MD, Room 263 Physics of Transport and Traffic | D-47048 Duisburg Institute of Physics | Phone: +49-203-379-3673 Department of Natural Sciences | Fax: +49-203-379-6564 University Duisburg-Essen | http://www.traffic.uni-duisburg.de/ ----------------------------------------------------------------------
