1 files changed, 52 insertions, 0 deletions
diff --git a/gcc/fortran/primary.c b/gcc/fortran/primary.c
index 7d2f9c7..e467e0b 100644
--- a/gcc/fortran/primary.c
+++ b/gcc/fortran/primary.c
@@ -736,6 +736,58 @@ done:
       gfc_internal_error ("gfc_range_check() returned bad value");
     }
 
+  /* Warn about trailing digits which suggest the user added too many
+     trailing digits, which may cause the appearance of higher pecision
+     than the kind kan support.
+
+     This is done by replacing the rightmost non-zero digit with zero
+     and comparing with the original value.  If these are equal, we
+     assume the user supplied more digits than intended (or forgot to
+     convert to the correct kind).
+  */
+
+  if (warn_conversion_extra)
+    {
+      mpfr_t r;
+      char *c, *p;
+      bool did_break;
+
+      c = strchr (buffer, 'e');
+      if (c == NULL)
+	c = buffer + strlen(buffer);
+
+      did_break = false;
+      for (p = c - 1; p >= buffer; p--)
+	{
+	  if (*p == '.')
+	    continue;
+	  
+	  if (*p != '0')
+	    {
+	      *p = '0';
+	      did_break = true;
+	      break;
+	    }
+	}
+
+      if (did_break)
+	{
+	  mpfr_init (r);
+	  mpfr_set_str (r, buffer, 10, GFC_RND_MODE);
+	  if (negate)
+	    mpfr_neg (r, r, GFC_RND_MODE);
+
+	  mpfr_sub (r, r, e->value.real, GFC_RND_MODE);
+
+	  if (mpfr_cmp_ui (r, 0) == 0)
+	    gfc_warning (OPT_Wconversion_extra, "Non-significant digits "
+			 "in %qs number at %C, maybe incorrect KIND",
+			 gfc_typename (&e->ts));
+
+	  mpfr_clear (r);
+	}
+    }
+
   *result = e;
   return MATCH_YES;