threads/strerror_tls.c

This is threads/strerror_tls.c (Listing 31-4, page 669), an example from the book, The Linux Programming Interface.

The source code file is copyright 2024, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

  Cover of The Linux Programming Interface
+/* strerror_tls.c
+
+   An implementation of strerror() that is made thread-safe through
+   the use of thread-local storage.
+
+   See also strerror_tsd.c.
+
+   Thread-local storage requires: Linux 2.6 or later, NPTL, and
+   gcc 3.3 or later.
+*/
 #define _GNU_SOURCE                 /* Get '_sys_nerr' and '_sys_errlist'
                                        declarations from <stdio.h> */
 #include <stdio.h>
 #include <string.h>                 /* Get declaration of strerror() */
 #include <pthread.h>
 
 #define MAX_ERROR_LEN 256           /* Maximum length of string in per-thread
                                        buffer returned by strerror() */
 
 static __thread char buf[MAX_ERROR_LEN];
                                     /* Thread-local return buffer */
 
 char *
 strerror(int err)
 {
     if (err < 0 || err >= _sys_nerr || _sys_errlist[err] == NULL) {
         snprintf(buf, MAX_ERROR_LEN, "Unknown error %d", err);
     } else {
         strncpy(buf, _sys_errlist[err], MAX_ERROR_LEN - 1);
         buf[MAX_ERROR_LEN - 1] = '\0';          /* Ensure null termination */
     }
 
     return buf;
 }

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