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malloc problem on ix86/darwin

From: Jasper Taylor
Subject: malloc problem on ix86/darwin
Date: Mon, 16 Apr 2007 13:33:04 +0100

Hello all,

I am using c code to add a structured database to my gprolog application. This code calls malloc() to extend the database when needed. It works OK under Linux (32- and 64-bit) and Windows but I am having problems under MacOS.

What happens is it works OK to start with but when the database reaches a certain size I get "child killed: bus error". Looking through the archives I saw that there are occasionally problems with the bits used in the addresses returned by malloc, so I added a wrapper that kept a mask of all bits so far used in malloced addresses and printed out whenever there were new ones. Here's the code for anyone interested:

long usedBits = NULL;
void* safe_malloc(count) {
  long ptr;

  ptr = (long)malloc(count);
  if (ptr & ~usedBits) {
    usedBits = usedBits|ptr;
    printf("debug_c malloc uses new bits, mask now %lx\n", usedBits);
  return (void*)ptr;

What happened was interesting: as long as everything was working properly, the mask of used bits was stable at 0x017ffff0. But every bus error was preceded by the mask growing to 0x117ffff0, i.e., the first time bit 28 is used, even though bits 27-25 and 23 are still so far unused. This is MacOS 10.4.9 with gcc 4.0.1 and gprolog 1.3.1

Is it possible that I should be using some alternative to malloc(), provided in gprolog.h? I can't find any reference to such a requirement in the documentation.

Any help very much appreciated!

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