errno/h_errno

[H. Peter Anvin]

On 2025-06-09 20:51, H. Peter Anvin wrote:
> 
> Ok, I grok that back in 2016 the tools might not have been ready yet, but in 2025?
> 

It is also perhaps worth noting that the errno TLS symbol is already 
globally exported and visible. This code works exactly as expected when 
linked against current glibc, either statically or dynamically:

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#undef errno
extern __thread int errno __attribute__((tls_model("initial-exec")));

int main(void)
{
     errno = 0;
     close(999);
     /* errno should be EBADF now */
     printf("errno = %d (%s), &errno = %p, __errno_location = %p\n",
	   errno, strerrorname_np(errno), &errno, __errno_location());
     return 0;
}