Re: Double free() in libc or gdb ?
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On Monday 12 March 2012 18:55:55 Konstantin Belousov wrote:
> On Mon, Mar 12, 2012 at 05:50:33PM +0100, Alexandre Martins wrote:
> > Dear all,
> >=20
> > I'm currently having some trouble with the dynamic loader.
> >=20
> > I have the libc compilled with "MALLOC_DEBUG" flag to detect double fre=
e.
> > When i run this piece of code (attached file) thought GDB, i have this
> > assertion :
> >=20
> > Assertion failed: ((run->regs_mask[elm] & (1U << bit)) =3D=3D 0), funct=
ion
> > arena_run_reg_dalloc, file /usr/src/lib/libc/stdlib/malloc.c, line 2543.
> >=20
> > But when i run the same binary without GDB, no assert.
> >=20
> > I'm very confused. Can you help me to debug that ?
>=20
> There is no attachment. Put the source somewhere on web.
Sorry, I'll past code here :
first.c:
____________________
#include <stdio.h>
void print_name(void)
{
printf("I'm " __FILE__ " at line %d\n", __LINE__);
}
____________________
second.c
____________________
#include <stdio.h>
void second_name(void)
{
printf("I'm " __FILE__ " at line %d\n", __LINE__);
}
void print_name(void)
{
printf("I'm " __FILE__ " at line %d\n", __LINE__);
}
____________________
main.c
____________________
#include <stdio.h>
#include <dlfcn.h>
extern void print_name(void);
int main(int argc, char *argv[])
{
void (*second_name)(void);
void *handle;
int count =3D 0;
while(42)
{
print_name();
handle =3D dlopen("second.so", RTLD_NOW);
print_name();
if (handle !=3D NULL)
{
second_name =3D dlsym(handle, "second_name");
if (second_name !=3D NULL)
{
printf("second : ");
second_name();
}
dlclose(handle);
}
else
fprintf(stderr, "Error : %s\n", dlerror());
}
}
____________________
Compilation and execution :
gcc -shared -O0 -g second.c -o second.so
gcc -shared -O0 -g first.c -o libfirst.so
gcc -O0 -g toto.c -lfirst -L. -o test
export LD_LIBRARY_PATH=3D$PWD
gdb ./test
Thank you for your help
=2D-=20
Alexandre Martins
NETASQ -- We secure IT
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