Re: posix_spawn issues on i686

[Jeremy Drake <cygwin@jdrake.com>]

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On Mon, 10 Jan 2022, Jeremy Drake wrote:

> From https://github.com/msys2/MSYS2-packages/issues/2801
>
> MSYS2 recently rebuilt GNU make 4.3, and I found that after rebuilding, it
> broke rather horribly on i686, where any attempt to run a command resulted
> in "Invalid argument" errors.  Some debugging revealed that rebuilding
> make resulted in it using posix_spawn now instead of vfork.  Passing
> --disable-posix-spawn to make's configure script results in a working i686
> make.
>

> Can you create a simple, self-contained testcase in plain C?


Sorry, I am not subscribed to the list so don't have the message to reply
to for threading purposes, but attached please find a C reproducer that
works on x86_64 but fails on i686.  The particular issue seems to be the
POSIX_SPAWN_RESETIDS flag - not setting that allows i686 to succeed too.

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#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <unistd.h>
#include <spawn.h>
#include <sys/wait.h>

extern char **environ;

int main()
{
    pid_t pid;
    char *argv[] = {"sh", "-c", "echo hi", NULL};
    posix_spawnattr_t attr;
    int status;
    short flags = POSIX_SPAWN_RESETIDS;

    if ((status = posix_spawnattr_init(&attr)) != 0) {
        printf("posix_spawnattr_init: %s\n", strerror(status));
	return status;
    }
    if ((status = posix_spawnattr_setflags(&attr, flags)) != 0) {
        printf("posix_spawnattr_setflags: %s\n", strerror(status));
	return status;
    }

    status = posix_spawn(&pid, "/bin/sh", NULL, &attr, argv, environ);
    if (status == 0) {
        printf("Child pid: %i\n", pid);
        do {
          if (waitpid(pid, &status, 0) != -1) {
            printf("Child status %d\n", WEXITSTATUS(status));
          } else {
            perror("waitpid");
            return 1;
          }
        } while (!WIFEXITED(status) && !WIFSIGNALED(status));
    } else {
        printf("posix_spawn: %s\n", strerror(status));
    }
    return status;
}