invoke.texi (-fno-builtin): Document that this is always on in C++.

	* invoke.texi (-fno-builtin): Document that this is always on
	in C++.

	* decl.c (duplicate_decls): Tidy.
	(init_decl_processing): Always set flag_no_builtin.

From-SVN: r42553

gcc/ChangeLog

+2001-05-24  Mark Mitchell  <mark@codesourcery.com>
+
+	* invoke.texi (-fno-builtin): Document that this is always on
+	in C++.
+
 2001-05-24  Philip Blundell  <philb@gnu.org>
 
 	* doc/install.texi (arm*-*-linux-gnu): Say that binutils 2.10 is

gcc/cp/ChangeLog

+2001-05-24  Mark Mitchell  <mark@codesourcery.com>
+
+	* decl.c (duplicate_decls): Tidy.
+	(init_decl_processing): Always set flag_no_builtin.
+
 2001-05-24  Nathan Sidwell  <nathan@codesourcery.com>
 
 	PR c++/2184

gcc/cp/decl.c

@@ -3717,11 +3717,8 @@ duplicate_decls (newdecl, olddecl)
 	    DECL_ARGUMENTS (newdecl) = DECL_ARGUMENTS (olddecl);
 	}
     }
-
-  if (TREE_CODE (newdecl) == NAMESPACE_DECL)
-    {
-      NAMESPACE_LEVEL (newdecl) = NAMESPACE_LEVEL (olddecl);
-    }
+  else if (TREE_CODE (newdecl) == NAMESPACE_DECL)
+    NAMESPACE_LEVEL (newdecl) = NAMESPACE_LEVEL (olddecl);
 
   /* Now preserve various other info from the definition.  */
   TREE_ADDRESSABLE (newdecl) = TREE_ADDRESSABLE (olddecl);
@@ -6372,6 +6369,12 @@ init_decl_processing ()
       flag_inline_functions = 0;
     }
 
+  /* In C++, we never create builtin functions whose name does not
+     begin with `__'.  Users should be using headers to get prototypes
+     in C++.  It would be nice if we could warn when `-fbuiltin' is
+     used explicitly, but we do not have that information.  */
+  flag_no_builtin = 1;
+
   /* Initially, C.  */
   current_lang_name = lang_name_c;
 

gcc/invoke.texi

@@ -972,6 +972,13 @@ and faster, but since the function calls no longer appear as such, you
 cannot set a breakpoint on those calls, nor can you change the behavior
 of the functions by linking with a different library.
 
+In C++, @samp{-fno-builtin} is always in effect.  The @samp{-fbuiltin}
+option has no effect.  Therefore, in C++, the only way to get the
+optimization benefits of builtin functions is to call the function
+using the @samp{__builtin_} prefix.  The GNU C++ Standard Library uses
+builtin functions to implement many functions (like
+@code{std::strchr}), so that you automatically get efficient code.
+
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