Re: [xen-4.0-testing test] 7147: regressions - FAIL

[Keir Fraser <keir@xen.org>]

On 23/05/2011 16:08, "Ian Jackson" <Ian.Jackson@eu.citrix.com> wrote:

> I wrote:
>> At top level:
>> cc1: error: unrecognized command line option "-Wno-unused-but-set-variable"
> 
> How about this fix.

I've been fiddling with a similar principle but much smaller patch (see
below). But it's failing for me in the same way as yours -- *all* optional
flags disappear from my CFLAGS (e.g., -Wno-unused-but-set-variable, which my
gcc-4.5.1 definitely does support).

So I'm still scratching my head on this one... :-(

diff -r 0f670f5146c8 Config.mk
--- a/Config.mk Sat May 21 07:55:46 2011 +0100
+++ b/Config.mk Mon May 23 16:16:54 2011 +0100
@@ -72,8 +72,10 @@ PYTHON_PREFIX_ARG ?= --prefix="$(PREFIX)
 
 # cc-option: Check if compiler supports first option, else fall back to
second.
 # Usage: cflags-y += $(call cc-option,$(CC),-march=winchip-c6,-march=i586)
-cc-option = $(shell if test -z "`$(1) $(2) -S -o /dev/null -xc \
-              /dev/null 2>&1`"; then echo "$(2)"; else echo "$(3)"; fi ;)
+#cc-option = $(shell if test -z "`$(1) $(2) -S -o /dev/null -xc \
+#              /dev/null 2>&1`"; then echo "$(2)"; else echo "$(3)"; fi ;)
+cc-option = $(shell if test -z "`echo 'void*p=1;' | \
+              $(1) $(2) -S -o /dev/null -xc - 2>&1`"; then echo "$(2)";
else echo "$(3)"; fi ;)
 
 # cc-option-add: Add an option to compilation flags, but only if supported.
 # Usage: $(call cc-option-add CFLAGS,CC,-march=winchip-c6)


> Ian.
> 
> diff -r 0f670f5146c8 Config.mk
> --- a/Config.mk Sat May 21 07:55:46 2011 +0100
> +++ b/Config.mk Mon May 23 16:07:59 2011 +0100
> @@ -72,8 +72,7 @@ PYTHON_PREFIX_ARG ?= --prefix="$(PREFIX)
>  
>  # cc-option: Check if compiler supports first option, else fall back to
> second.
>  # Usage: cflags-y += $(call cc-option,$(CC),-march=winchip-c6,-march=i586)
> -cc-option = $(shell if test -z "`$(1) $(2) -S -o /dev/null -xc \
> -              /dev/null 2>&1`"; then echo "$(2)"; else echo "$(3)"; fi ;)
> +cc-option = $(shell $(XEN_ROOT)/config/test-cc-option.sh $(1) $(2) $(3))
>  
>  # cc-option-add: Add an option to compilation flags, but only if supported.
>  # Usage: $(call cc-option-add CFLAGS,CC,-march=winchip-c6)
> diff -r 0f670f5146c8 config/test-cc-option.sh
> --- /dev/null Thu Jan 01 00:00:00 1970 +0000
> +++ b/config/test-cc-option.sh Mon May 23 16:07:59 2011 +0100
> @@ -0,0 +1,31 @@
> +#!/bin/sh
> +set -e
> +
> +cc="$1"
> +opt="$2"
> +alt="$3"
> +
> +case "$opt" in
> +-Wno-*)
> +   # Sadly a broken implementation of the fix to GCC PR 28322
> +   # (actually shipped eg in Debian lenny) makes it hard to spot
> +   # whether the compiler recognises a -Wno-foo option without
> +   # generating a warning for some other reason.
> +
> +   input="${0%-cc-option.sh}-cc-warning.c"
> +   if $cc $opt -Wreturn-type -Wno-error -S -o /dev/null "$input" \
> +           >/dev/null 2>&1; then
> +       res="$opt"
> +   else
> +       res="$alt"
> +   fi
> +   ;;
> +*)
> +    if test -z "`$cc $opt $nerr -S -o /dev/null -xc $input 2>&1`"; then
> +        res="$opt"
> +    else
> +        res="$alt"
> +    fi
> +    ;;
> +esac
> +printf "%s\n" "$res"
> diff -r 0f670f5146c8 config/test-cc-warning.c
> --- /dev/null Thu Jan 01 00:00:00 1970 +0000
> +++ b/config/test-cc-warning.c Mon May 23 16:07:59 2011 +0100
> @@ -0,0 +1,2 @@
> +extern int bogus(void);
> +int bogus(void) { }