[PATCH] Support -fno-builtin-foo options in C++

[Roger Sayle <roger at eyesopen dot com>]

This patch originally started life as a documentation correction.
Since builtin functions were re-enabled in C++ for GCC v3.1, the
"-fno-builtin" is now functional again.  However reading the
affected documentation, I realized there's also no reason that
g++ doesn't also support "-fno-builtin-foo" to disable the
builtin function "foo" (in C++ terms this disables both "::foo"
and "std::foo").  This option is now available on all C-family
front-ends.

Tested with a complete bootstrap and "make -k check", all languages
except Ada and treelang, on i686-pc-linux-gnu with no new regressions.

Ok for mainline?


2002-07-14  Roger Sayle  <roger@eyesopen.com>

	* cp/decl2.c (cxx_decode_option): Support -fno-builtin-foo.

	* doc/invoke.texi: Document that both -fno-builtin-foo and
	-fno-builtin are supported by the g++ front-end.


Index: cp/decl2.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/decl2.c,v
retrieving revision 1.545
diff -c -3 -p -r1.545 decl2.c
*** cp/decl2.c	9 Jul 2002 23:31:28 -0000	1.545
--- cp/decl2.c	14 Jul 2002 04:57:52 -0000
*************** cxx_decode_option (argc, argv)
*** 540,545 ****
--- 540,547 ----
  	  warning ("-fname-mangling-version is no longer supported");
  	  return 1;
  	}
+       else if ((option_value = skip_leading_substring (p, "no-builtin-")))
+ 	disable_builtin_function (option_value);
        else if (dump_switch_p (p))
  	;
        else
Index: doc/invoke.texi
===================================================================
RCS file: /cvs/gcc/gcc/gcc/doc/invoke.texi,v
retrieving revision 1.155
diff -c -3 -p -r1.155 invoke.texi
*** doc/invoke.texi	10 Jul 2002 19:17:51 -0000	1.155
--- doc/invoke.texi	14 Jul 2002 04:57:54 -0000
*************** switch only affects the @code{asm} and @
*** 1079,1085 ****
  @code{inline} is a standard keyword in ISO C99.

  @item -fno-builtin
! @itemx -fno-builtin-@var{function} @r{(C and Objective-C only)}
  @opindex fno-builtin
  @cindex built-in functions
  Don't recognize built-in functions that do not begin with
--- 1079,1085 ----
  @code{inline} is a standard keyword in ISO C99.

  @item -fno-builtin
! @itemx -fno-builtin-@var{function}
  @opindex fno-builtin
  @cindex built-in functions
  Don't recognize built-in functions that do not begin with
*************** and faster, but since the function calls
*** 1097,1111 ****
  cannot set a breakpoint on those calls, nor can you change the behavior
  of the functions by linking with a different library.

! In C++, @option{-fno-builtin} is always in effect.  The @option{-fbuiltin}
! option has no effect.  Therefore, in C++, the only way to get the
! optimization benefits of built-in functions is to call the function
! using the @samp{__builtin_} prefix.  The GNU C++ Standard Library uses
! built-in functions to implement many functions (like
! @code{std::strchr}), so that you automatically get efficient code.
!
! With the @option{-fno-builtin-@var{function}} option, not available
! when compiling C++, only the built-in function @var{function} is
  disabled.  @var{function} must not begin with @samp{__builtin_}.  If a
  function is named this is not built-in in this version of GCC, this
  option is ignored.  There is no corresponding
--- 1097,1104 ----
  cannot set a breakpoint on those calls, nor can you change the behavior
  of the functions by linking with a different library.

! With the @option{-fno-builtin-@var{function}} option
! only the built-in function @var{function} is
  disabled.  @var{function} must not begin with @samp{__builtin_}.  If a
  function is named this is not built-in in this version of GCC, this
  option is ignored.  There is no corresponding

Roger
--
Roger Sayle,                         E-mail: roger@eyesopen.com
OpenEye Scientific Software,         WWW: http://www.eyesopen.com/
Suite 1107, 3600 Cerrillos Road,     Tel: (+1) 505-473-7385
Santa Fe, New Mexico, 87507.         Fax: (+1) 505-473-0833