python / python/cpython

Setting resource.RLIMIT_STACK not working on MacOS

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OS-mac stdlib type-bug
Dominant language
Python
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Description

Bug report

Bug description:

Running

python3.14 -c "import resource; resource.setrlimit(resource.RLIMIT_STACK, resource.getrlimit(resource.RLIMIT_STACK))"

On MacOS 15.7.2 on my M4 Macbook produces the following error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import resource; resource.setrlimit(resource.RLIMIT_STACK, resource.getrlimit(resource.RLIMIT_STACK))
                     ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: current limit exceeds maximum limit

Given we are setting the limit to what it was previously, I would not expect this to exceed the maximum limit, because we are not actually changing any limits. The following c program works without issue

#include <stdio.h>
#include <errno.h>
#include <sys/resource.h>

int main(void)
{
    struct rlimit limits = {
        8372224,
        60792480
    };
    int r = setrlimit(RLIMIT_STACK, &limits);
    if (r == -1) {
        perror("setrlimit");
        return 1;
    }
    return 0;
}

(The limits I am setting there are the defaults that python reports).

This seems to be related to #78783.

CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs
  • gh-150170

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the reported Python command using resource.setrlimit and resource.getrlimit on macOS, then review related issue #78783 and linked PR gh-150170. Done means setting RLIMIT_STACK to the values returned by getrlimit no longer raises ValueError on the reported macOS configuration.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
operating-systems
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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