threads/strerror_tls.c

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

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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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