[php-src] Issue #8240: Misleading error message on popen() when /bin/sh is missing

Issue: https://github.com/php/php-src/issues/8240 Comment Author: arnaud-lb Hello I confirm. The glibc popen() function sets errno to ENOMEM (Cannot allocate memory) when it fails to spawn the command. This can be seen here: https://sourceware.org/git/?p=glibc.git;a=blob;f=libio/iopopen.c;h=06778cf110ef9b2745664df00bfd37f291e23ff3;hb=HEAD#l210 This can be reproduced with this C code: ``` c // test.c #include <stdio.h> #include <errno.h> #include <string.h> int main() { errno = 0; FILE * f = popen("/bin/true", "r"); fprintf(stderr, "f: %px, errno: %d, strerror: %s\n", f, errno, strerror(errno)); } ``` ``` ; gcc -static -o test test.c ; sudo chroot . /test f: (nil)x, errno: 12, strerror: Cannot allocate memory ``` The gnu man page mentions something about memory allocations and errno: > The popen() function does not set errno if memory allocation fails. So it _may_ done on purpose. However, this doesn't appears to be standard behavior. Compiling against musl libc has different results: ``` ; musl-gcc -static -o test test.c ; sudo chroot . /test f: 0x, errno: 2, strerror: No such file or directory ``` We could trigger a different error when errno is ENOMEM, but other libcs appear to set errno to ENOMEM to indicate memory allocation failures.