c-tree.h (warn_float_equal): Declare.

        * c-tree.h (warn_float_equal): Declare.
        * c-decl.c (warn_float_equal): Define.
        (c_decode_option): Recognize -W[no-]float-equal.
        * c-typeck.c (build_binary_op): Conditionally warn
        about equality tests of floating point types.
        * toplev.c (documented_lan_options): Add -W[no-]float-equal.

From-SVN: r29722

gcc/ChangeLog

+Thu Sep 30 00:13:27 1999  Dirk Zoller  <duz@rtsffm.com>
+
+	* c-tree.h (warn_float_equal): Declare.
+	* c-decl.c (warn_float_equal): Define.
+	(c_decode_option): Recognize -W[no-]float-equal.
+	* c-typeck.c (build_binary_op): Conditionally warn
+	about equality tests of floating point types.
+	* toplev.c (documented_lan_options): Add -W[no-]float-equal.
+
 Wed Sep 29 23:43:39 1999  Jeffrey A Law  (law@cygnus.com)
 
 	* cse.c (struct set): Delete inner_dest_loc field. 

gcc/c-decl.c

@@ -446,6 +446,10 @@ int warn_unknown_pragmas = 0; /* Tri state variable.  */
 
 int warn_sign_compare = -1;
 
+/* Warn about testing equality of floating point numbers. */
+
+int warn_float_equal = 0;
+
 /* Nonzero means warn about use of multicharacter literals.  */
 
 int warn_multichar = 1;
@@ -724,6 +728,10 @@ c_decode_option (argc, argv)
     warn_sign_compare = 1;
   else if (!strcmp (p, "-Wno-sign-compare"))
     warn_sign_compare = 0;
+  else if (!strcmp (p, "-Wfloat-equal"))
+    warn_float_equal = 1;
+  else if (!strcmp (p, "-Wno-float-equal"))
+    warn_float_equal = 0;
   else if (!strcmp (p, "-Wmultichar"))
     warn_multichar = 1;
   else if (!strcmp (p, "-Wno-multichar"))

gcc/c-tree.h

@@ -422,6 +422,10 @@ extern int warn_missing_braces;
 
 extern int warn_sign_compare;
 
+/* Warn about testing equality of floating point numbers. */
+
+extern int warn_float_equal;
+
 /* Warn about multicharacter constants.  */
 
 extern int warn_multichar;

gcc/c-typeck.c

@@ -2099,6 +2099,8 @@ build_binary_op (code, orig_op0, orig_op1, convert_p)
 
     case EQ_EXPR:
     case NE_EXPR:
+      if (warn_float_equal && (code0 == REAL_TYPE || code1 == REAL_TYPE))
+	warning ("comparing floating point with == or != is unsafe");
       /* Result of comparison is always int,
 	 but don't convert the args to int!  */
       build_type = integer_type_node;

gcc/toplev.c

@@ -1100,6 +1100,8 @@ documented_lang_options[] =
   { "-Wno-redundant-decls", "" },
   { "-Wsign-compare", "Warn about signed/unsigned comparisons" },
   { "-Wno-sign-compare", "" },
+  { "-Wfloat-equal", "Warn about testing equality of floating point numbers" },
+  { "-Wno-float-equal", "" },
   { "-Wunknown-pragmas", "Warn about unrecognised pragmas" },
   { "-Wno-unknown-pragmas", "" },
   { "-Wstrict-prototypes", "Warn about non-prototyped function decls" },