[New-bugs-announce] [issue34602] python3 resource.setrlimit strange behaviour under macOS

[marche147]

New submission from marche147 <bitmarche at gmail.com>:

Consider the following code:

```
import resource
s, h = resource.getrlimit(resource.RLIMIT_STACK)
resource.setrlimit(resource.RLIMIT_STACK, (h, h))
```

Running this under macOS with python 3.6.5 gives the following exception:

```
bash-3.2$ uname -a
Darwin arch-osx 17.7.0 Darwin Kernel Version 17.7.0: Thu Jun 21 22:53:14 PDT 2018; root:xnu-4570.71.2~1/RELEASE_X86_64 x86_64
bash-3.2$ cat test.py
import resource
s, h = resource.getrlimit(resource.RLIMIT_STACK)
resource.setrlimit(resource.RLIMIT_STACK, (h, h))
bash-3.2$ python3 test.py
Traceback (most recent call last):
  File "test.py", line 3, in <module>
    resource.setrlimit(resource.RLIMIT_STACK, (h, h))
ValueError: current limit exceeds maximum limit
```

Nevertheless, when using python 2.7.10 under the same environment, this code works perfectly without exceptions being thrown. Additionally, neither of these operations fail under the same circumstances :

```
bash-3.2$ cat test.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/resource.h>

int main() {
  struct rlimit rl;
  if(getrlimit(RLIMIT_STACK, &rl) < 0) {
    perror("getrlimit");
    exit(1);
  }

  rl.rlim_cur = rl.rlim_max;
  if(setrlimit(RLIMIT_STACK, &rl) < 0) {
    perror("setrlimit");
    exit(1);
  }
  return 0;
}
bash-3.2$ gcc -o test test.c
bash-3.2$ ./test
```

```
bash-3.2$ ulimit -s -H
65532
bash-3.2$ ulimit -s
8192
bash-3.2$ ulimit -s 65532
bash-3.2$ ulimit -s
65532
```

I have also tried to run the above-mentioned python script on linux, also it does not generate exceptions both on python2 (2.7.10) & python3 (3.6.5).

----------
components: Library (Lib)
messages: 324731
nosy: marche147
priority: normal
severity: normal
status: open
title: python3 resource.setrlimit strange behaviour under macOS
type: behavior
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34602>
_______________________________________