PyMem_MALLOC (was [Python-Dev] Snake farm) (original) (raw)

M.-A. Lemburg mal@lemburg.com
Fri, 22 Nov 2002 16:52:20 +0100

arc Recht wrote:

>> > So it looks like PyOblectFree() was called with 0x800 as an argument, >> > which is a bogus pointer value. Can you go up one stack level and see >> > what the value of k in functioncall() is? >> 713 if (ADDRESSINRANGE(p, pool->arenaindex)) { >> (gdb) up >> # 1 0x080dfef4 in functioncall (func=0x826317c, arg=0x8256aac, >> kw=0x8269bdc) at Objects/funcobject.c:481 >> 481 PyMemDEL(k); >> (gdb) p k >> $1 = (struct object **) 0x800 > > > Well, then maybe you can follow MvL's suggestion and find out how come > this value was returned by PyMemNEW(PyObject , 2nk)???

The problem seems to be in the FreeBSD malloc implementation. malloc(0) returns 0x800 in all my tests. malloc(1) and up seems to work properly..

Maybe we have to relax the configure test a bit and set the MALLOC_ZERO_RETURNS_NULL #define not only on NULL returns, but on returns < 0x1000 as well ?! (or add something to pyport.h along these lines specific to FreeBSD)...

check whether malloc(0) returns NULL or not

AC_MSG_CHECKING(what malloc(0) returns) AC_CACHE_VAL(ac_cv_malloc_zero, [AC_TRY_RUN([#include <stdio.h> #ifdef HAVE_STDLIB #include <stdlib.h> #else char *malloc(), *realloc(); int *free(); #endif main() { char *p; p = malloc(0); if ((unsigned long)p < 0x1000) exit(1); p = realloc(p, 0); if ((unsigned long)p < 0x1000) exit(1); free(p); exit(0); }], ac_cv_malloc_zero=nonnull, ac_cv_malloc_zero=null, ac_cv_malloc_zero=nonnull)]) # XXX arm cross-compile? AC_MSG_RESULT($ac_cv_malloc_zero) if test "$ac_cv_malloc_zero" = null then AC_DEFINE(MALLOC_ZERO_RETURNS_NULL, 1, [Define if malloc(0) returns a NULL pointer.]) fi

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