Re: [PATCH 1/2] Fix -fno-lto (PR lto/46905)

[Andi Kleen <andi@firstfloor.org>]

On Thu, Dec 16, 2010 at 03:39:33PM +0000, Joseph S. Myers wrote:
> On Thu, 16 Dec 2010, Richard Guenther wrote:
> 
> > > I also tried to do it without opts.c, but setting an 0 initialization
> > > value for the -fno-lto entry, but that didn't work either.
> > 
> > Huh, that's strange.  Joseph, do you have any idea why?  Is it because
> > of how flags get passed to collect2?
> 
> Having both flto and fno-lto in common.opt seems dodgy.  Try making the 
> code in opts.c that handles OPT_flto check "value" (value == 0 meaning 
> -fno-lto) instead.

That worked. Here's an updated version. Ok now?

From: Andi Kleen <ak@linux.intel.com>
Date: Wed, 15 Dec 2010 20:10:22 +0100
Subject: [PATCH] Fix -fno-lto (PR lto/46905)

This fixes PR lto/46905.

It's sometimes convenient in large Makefiles to globally enable LTO
in CFLAGS, but disable it again for specific files. The simplest
way to do that is appending -fno-lto, but that didn't work.
Add explicit code to handle this case.

gcc/

2010-12-15  Andi Kleen	<ak@linux.intel.com>

	PR lto/46905
	* collect2.c (main): Handle -fno-lto.
	* common.opt (fno-lto): Add.
	* opts.c (common_handle_option): Handle OPT_fno_lto.

diff --git a/gcc/collect2.c b/gcc/collect2.c
index 89b21d5..77f794f 100644
--- a/gcc/collect2.c
+++ b/gcc/collect2.c
@@ -1211,6 +1211,8 @@ main (int argc, char **argv)
         else if ((! strncmp (argv[i], "-flto=", 6)
 		  || ! strcmp (argv[i], "-flto")) && ! use_plugin)
 	  lto_mode = LTO_MODE_WHOPR;
+	else if (!strncmp (argv[i], "-fno-lto", 8))
+	  lto_mode = LTO_MODE_NONE;
         else if (! strcmp (argv[i], "-plugin"))
 	  {
 	    use_plugin = true;
diff --git a/gcc/opts.c b/gcc/opts.c
index 2c8e767..cc4181e 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1670,7 +1670,7 @@ common_handle_option (struct gcc_options *opts,
       break;
 
     case OPT_flto:
-      opts->x_flag_lto = "";
+      opts->x_flag_lto = value ? "" : NULL;
       break;
 
     case OPT_w: