threads/strerror_test.c

This is threads/strerror_test.c (Listing 31-2, page 665), an example from the book, The Linux Programming Interface.

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Cover of The Linux Programming Interface

+/* strerror_test.c
+
+   A program to test whether the implementation of strerror() thread-safe.
+*/
 #include <stdio.h>
 #include <string.h>                 /* Get declaration of strerror() */
 #include <pthread.h>
 #include "tlpi_hdr.h"
 
 static void *
 threadFunc(void *arg)
 {
     char *str;
 
     printf("Other thread about to call strerror()\n");
     str = strerror(EPERM);
     printf("Other thread: str (%p) = %s\n", str, str);
 
     return NULL;
 }
 
 int
 main(int argc, char *argv[])
 {
     pthread_t t;
     int s;
     char *str;
 
     str = strerror(EINVAL);
     printf("Main thread has called strerror()\n");
 
     s = pthread_create(&t, NULL, threadFunc, NULL);
     if (s != 0)
         errExitEN(s, "pthread_create");
 
     s = pthread_join(t, NULL);
     if (s != 0)
         errExitEN(s, "pthread_join");
 
+    /* If strerror() is not thread-safe, then the output of this printf() be
+       the same as that produced by the analogous printf() in threadFunc() */
+
     printf("Main thread:  str (%p) = %s\n", str, str);
 
     exit(EXIT_SUCCESS);
 }

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