X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;ds=sidebyside;f=tests%2Ftest-fwriting.c;h=a16213046373790b0cdf636d419641f14154cba2;hb=a7ebfd1caaa58b6a7bc0b1d1510b0255604e804a;hp=00b6870b4a31f7c2192c2c8b2f6d42377658e49f;hpb=503e2514a1404a19a00117845216993a3c2ccf5f;p=gnulib.git

diff --git a/tests/test-fwriting.c b/tests/test-fwriting.c
index 00b6870b4..a16213046 100644
--- a/tests/test-fwriting.c
+++ b/tests/test-fwriting.c
@@ -21,9 +21,19 @@
 
 #include "fwriting.h"
 
+#include <stdio.h>
 #include <stdlib.h>
 
-#define ASSERT(expr) if (!(expr)) abort ();
+#define ASSERT(expr) \
+  do									     \
+    {									     \
+      if (!(expr))							     \
+        {								     \
+          fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+          abort ();							     \
+        }								     \
+    }									     \
+  while (0)
 
 #define TESTFILE "t-fwriting.tmp"
 
@@ -73,6 +83,7 @@ main ()
      fwriting is only deterministic after input or output, but this
      test case should be portable even on open, after reposition, and
      after fflush.  */
+  /* First a scenario with only fgetc, fseek, fputc.  */
   fp = fopen (TESTFILE, "r+");
   if (fp == NULL)
     goto skip;
@@ -91,12 +102,14 @@ main ()
   if (fseek (fp, 0, SEEK_CUR) != 0)
     goto skip;
   ASSERT (!fwriting (fp));
-  if (fputc ('z', fp) != 'z')
+  if (fputc ('x', fp) != 'x')
     goto skip;
   ASSERT (fwriting (fp));
   if (fseek (fp, 0, SEEK_END))
     goto skip;
-  /* fwriting (fp) is undefined here, but freading (fp) is false.  */
+  /* freading (fp) is undefined here, because on some implementations (e.g.
+     glibc) fseek causes a buffer to be read.
+     fwriting (fp) is undefined as well.  */
   if (fclose (fp))
     goto skip;
 
@@ -105,6 +118,7 @@ main ()
      fwriting is only deterministic after input or output, but this
      test case should be portable even on open, after reposition, and
      after fflush.  */
+  /* Here a scenario that includes fflush.  */
   fp = fopen (TESTFILE, "r+");
   if (fp == NULL)
     goto skip;
@@ -120,7 +134,7 @@ main ()
   ASSERT (!fwriting (fp));
   fflush (fp);
   ASSERT (!fwriting (fp));
-  if (fgetc (fp) != 'a')
+  if (fgetc (fp) != 'x')
     goto skip;
   ASSERT (!fwriting (fp));
   /* This fseek call is necessary when switching from reading to writing.
@@ -133,7 +147,9 @@ main ()
   ASSERT (fwriting (fp));
   if (fseek (fp, 0, SEEK_END))
     goto skip;
-  /* fwriting (fp) is undefined here, but freading (fp) is false.  */
+  /* freading (fp) is undefined here, because on some implementations (e.g.
+     glibc) fseek causes a buffer to be read.
+     fwriting (fp) is undefined as well.  */
   if (fclose (fp))
     goto skip;