re PR c++/9393 (Anonymous namespaces and compiling the same file twice)

	PR c++/9393
	* doc/invoke.texi (Debugging Options): Document -frandom-seed.
	* configure.in: Check for gettimeofday.
	* tree.c (flag_random_seed): Define.
	(default_flag_random_seed): New.
	(append_random_chars): Use flag_random_seed rather than trying
	to acquire randomness here.
	* tree.h (default_flag_random_seed): Declare.
	* toplev.c (display_help): Add -frandom-seed and -fstack-limit-*
	descriptions.
	(decode_f_option): Handle -frandom-seed.
	(print_switch_values): Call default_flag_random_seed.
	* flags.h (flag_random_seed): Declare.
	* configure: Regenerate.
	* config.in: Regenerate.
	* config/alpha/t-crtfm: Use -frandom-seed.

From-SVN: r65500

1 files changed, 40 insertions, 28 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index 57d76b4..fc4630f 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -4294,6 +4294,38 @@ dump_tree_statistics ()
 
 #define FILE_FUNCTION_FORMAT "_GLOBAL__%s_%s"
 
+const char *flag_random_seed;
+
+/* Set up a default flag_random_seed value, if there wasn't one already.  */
+
+void
+default_flag_random_seed (void)
+{
+  unsigned HOST_WIDE_INT value;
+  char *new_random_seed;
+  
+  if (flag_random_seed != NULL)
+    return;
+
+  /* Get some more or less random data.  */
+#ifdef HAVE_GETTIMEOFDAY
+ {
+   struct timeval tv;
+   
+   gettimeofday (&tv, NULL);
+   value = (((unsigned HOST_WIDE_INT) tv.tv_usec << 16) 
+	    ^ tv.tv_sec ^ getpid ());
+ }
+#else
+  value = getpid ();
+#endif
+
+  /* This slightly overestimates the space required.  */
+  new_random_seed = xmalloc (HOST_BITS_PER_WIDE_INT / 3 + 2);
+  sprintf (new_random_seed, HOST_WIDE_INT_PRINT_UNSIGNED, value);
+  flag_random_seed = new_random_seed;
+}
+
 /* Appends 6 random characters to TEMPLATE to (hopefully) avoid name
    clashes in cases where we can't reliably choose a unique name.
 
@@ -4305,40 +4337,20 @@ append_random_chars (template)
 {
   static const char letters[]
     = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
-  static unsigned HOST_WIDE_INT value;
   unsigned HOST_WIDE_INT v;
+  size_t i;
 
-  if (! value)
-    {
-      struct stat st;
+  default_flag_random_seed ();
 
-      /* VALUE should be unique for each file and must not change between
-	 compiles since this can cause bootstrap comparison errors.  */
-
-      if (stat (main_input_filename, &st) < 0)
-	{
-	  /* This can happen when preprocessed text is shipped between
-	     machines, e.g. with bug reports.  Assume that uniqueness
-	     isn't actually an issue.  */
-	  value = 1;
-	}
-      else
-	{
-	  /* In VMS, ino is an array, so we have to use both values.  We
-	     conditionalize that.  */
-#ifdef VMS
-#define INO_TO_INT(INO) ((int) (INO)[1] << 16 ^ (int) (INO)[2])
-#else
-#define INO_TO_INT(INO) INO
-#endif
-	  value = st.st_dev ^ INO_TO_INT (st.st_ino) ^ st.st_mtime;
-	}
-    }
+  /* This isn't a very good hash, but it does guarantee no collisions 
+     when the random string is generated by the code above and the time
+     delta is small.  */
+  v = 0;
+  for (i = 0; i < strlen (flag_random_seed); i++)
+    v = (v << 4) ^ (v >> (HOST_BITS_PER_WIDE_INT - 4)) ^ flag_random_seed[i];
 
   template += strlen (template);
 
-  v = value;
-
   /* Fill in the random bits.  */
   template[0] = letters[v % 62];
   v /= 62;