RE: [bug #18396] stack size setrlimit call interacts badly with Solaris/x86 kernel bug

[Martin Dorey]

> However, your point about programs invoked by make inheriting the 
> setrlimit() is definitely something that seems problematic.  Perhaps
GNU 
> make could change the stack limit back to what it was after it forks
but 
> before it execs its child.  I wonder what happens if you change a
limit to 
> something too small for the current processes resources?

It doesn't look specified by
http://www.opengroup.org/onlinepubs/009695399/functions/getrlimit.html.

This test suggests that it works fine on my Linux box.  I presume the
limit check is normally done on a faulting access off the end of the
stack, so setrlimit would need some to have some different and special
code to check the current stack usage if it wanted to apply the check
immediately.  It seems a bit unlikely that anyone would have gone to
that effort, thus stopping you from doing something useful in this sort
of situation.

#include <alloca.h>
#include <errno.h>
#include <iostream>
#include <stddef.h>
#include <string.h>
#include <sys/time.h>
#include <sys/resource.h>

void useLotsOfStack(size_t size);

size_t getAndDisplayStackLimit() {
  rlimit resourceLimit;
  if (getrlimit(RLIMIT_STACK, &resourceLimit) < 0) {
    std::cerr << "getrlimit failed with " << errno << std::endl;
  }
  std::cout << "rlim_cur == " << resourceLimit.rlim_cur << std::endl;
  std::cout << "rlim_max == " << resourceLimit.rlim_max << std::endl;
  return resourceLimit.rlim_cur;
}

void setStackLimit(size_t size) {
  rlimit resourceLimit;
  resourceLimit.rlim_cur = size;
  if (setrlimit(RLIMIT_STACK, &resourceLimit) < 0) {
    std::cerr << "setrlimit failed with " << errno << std::endl;
    exit(1);
  }
  getAndDisplayStackLimit();
}

int main() {
  size_t initialLimit = getAndDisplayStackLimit();
  //useLotsOfStack(initialLimit * 10);
  setStackLimit(initialLimit * 100);
  useLotsOfStack(initialLimit * 10);
  setStackLimit(initialLimit);
  useLotsOfStack(initialLimit * 10);
}

void useLotsOfStack(size_t size) {
  memset(alloca(size), 0, size);
}
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Martin's Outlook, BlueArc Engineering