[fpc-devel] Possible memory leak in cthread.

Jonas Maebe jonas.maebe at elis.ugent.be
Wed Aug 5 14:19:56 CEST 2009

On 05 Aug 2009, at 13:55, Wimpie Nortje wrote:

> program memleak;
> {$mode objfpc}{$H+}
> uses
> cthreads;
> begin
> end.
> If I run the program using valgrind I get the following output:
> ==1944==    Invalid free() / delete /  
> delete[]                                                              
> ==1944==    at 0x4025DFA: free (vg_replace_malloc.c:323)              
> ==1944==    by 0x4171664: (within /lib/tls/i686/cmov/libc-2.9.so)
> ==1944==    by 0x4020422: _vgnU_freeres (vg_preloaded.c:60)
> ==1944==    by 0x40E5B23: _Exit (in /lib/tls/i686/cmov/libc-2.9.so)
> ==1944==    by 0x405C77C: (below main) (in /lib/tls/i686/cmov/ 
> libc-2.9.so)
> ==1944==  Address 0xffffffff is not stack'd, malloc'd or (recently)  
> free'd

This invalid free is probably the reason for the memory leak.

It even happens for this program:

{$linklib c}

There is probably some error in FPC's startup code (the code in fpc/ 
rtl/linux/i386/cprt0.as) which doesn't initialise some libc pointer.  
You should indeed report a bug about this.

To Graeme and Michael: heaptrc is useless/irrelevant to analyse memory  
leaks reported inside libc. Such errors can always be due to wrong  
usage of the C library from within FPC code.


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