Is malloc signal-"tolerant"?

[Stefan Hoffmeister]

Hi,

it is a well-documented fact that malloc is not a signal-safe function -
i.e. it cannot be called from the context of a signal handler.

But is malloc signal-"tolerant" in that its internal data structures
survive a longjmp() (or a siglongjmp()) out of a signal handler?

Given this program, for instance, which basically exercises malloc and
free in a very tight loop,

***************************
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <setjmp.h>
#include <string.h>

sigjmp_buf JumpBuffer;
int Loop = 1;

void SignalIntHandler(int SignalNumber)
{
  siglongjmp(JumpBuffer, 1);
}

void SignalQuitHandler(int SignalNumber)
{
  Loop = 0;
}

void LoopWithFun()
{
  sigsetjmp(JumpBuffer, 1);

  while (Loop)
  {
    int MemSize = rand();

    free(malloc(MemSize));
  }
}

int main(int argc, char *argv[])
{
  struct sigaction sa;

  printf("Starting the fun\r\n");

  memset(&sa, sizeof(sa), 0);

  sa.sa_handler = SignalIntHandler;
  sa.sa_flags = SA_RESTART;
  sigaction(SIGINT, &sa, 0);

  sa.sa_handler = SignalQuitHandler;
  sa.sa_flags = SA_RESTART;
  sigaction(SIGQUIT, &sa, 0);

  LoopWithFun();

  printf("Done\n");

  return 0;
}
***************************

and a shell command on a separate terminal 

  while true; do killall -INT TheAboveProgram; done

that essentially keeps signalling to the test program - should this
survive?

[This would imply that the for the duration of a malloc operation,
certain signals are blocked - I cannot imagine any other way to
guarantee signal-atomic operations.]

Currently the above test scenario terminates with a SIGSEGV after a
while (glibc 2.2.4, kernel 2.4.17), presumably because either malloc or
free were disturbed by the siglongjmp() while updating some rather
important data structure.

TIA!
Stefan