--- libgcc2.c-original	Tue Mar 20 19:22:16 2001
+++ libgcc2.c	Wed Mar 21 12:33:57 2001
@@ -1459,6 +1459,10 @@ char *ctime ();
 #include "gcov-io.h"
 #include <string.h>

+/* For O_RDWR and O_CREAT */
+#include <fcntl.h>
+#include <errno.h>
+
 static struct bb *bb_head;

 /* Return the number of digits needed to print a value */
@@ -1478,6 +1482,23 @@ static struct bb *bb_head;
   return ret;
 }

+/* Opens a file, locking it for exclusive access. Used for .da files
+ * below. If locking is not available, define it as fopen(name,
+ * "rw"). */
+static FILE *
+lopen(const char *name)
+{
+  int fd = open(name, O_RDWR | O_CREAT, 0666);
+  if (fd < 0)
+    return NULL;
+
+  while ( (lockf(fd, F_LOCK, 0) < 0))
+    if (errno != EINTR)
+      return NULL;
+
+  return fdopen(fd, "r+b");
+}
+
 void
 __bb_exit_func (void)
 {
@@ -1499,21 +1520,21 @@ __bb_exit_func (void)

       for (ptr = bb_head; ptr != (struct bb *) 0; ptr = ptr->next)
 	{
+	  long n_counts = 0;
+
 	  /* If the file exists, and the number of counts in it is the same,
 	     then merge them in.  */
-
-	  if ((da_file = fopen (ptr->filename, "r")) != 0)
-	    {
-	      long n_counts = 0;
-
-	      if (__read_long (&n_counts, da_file, 8) != 0)
-		{
-		  fprintf (stderr, "arc profiling: Can't read output file %s.\n",
-			   ptr->filename);
-		  continue;
-		}

-	      if (n_counts == ptr->ncounts)
+
+	  if ((da_file = lopen (ptr->filename)) == 0)
+	    {
+	      fprintf (stderr, "arc profiling: Can't open output file %s.\n",
+		       ptr->filename);
+	      continue;
+	    }
+
+	  if ( (__read_long (&n_counts, da_file, 8) == 0)
+	       && (n_counts == ptr->ncounts) )
 		{
 		  int i;

@@ -1530,17 +1551,10 @@ __bb_exit_func (void)
 		      ptr->counts[i] += v;
 		    }
 		}
-
-	      if (fclose (da_file) == EOF)
-		fprintf (stderr, "arc profiling: Error closing output file %s.\n",
-			 ptr->filename);
-	    }
-	  if ((da_file = fopen (ptr->filename, "w")) == 0)
-	    {
-	      fprintf (stderr, "arc profiling: Can't open output file %s.\n",
-		       ptr->filename);
-	      continue;
-	    }
+
+          /* Perhaps we should also truncate the file before
+	   * writing? */
+	  rewind(da_file);

 	  /* ??? Should first write a header to the file.  Preferably, a 4 byte
 	     magic number, 4 bytes containing the time the program was