[Qemu-devel] [PATCH] configure: change endian cross compilation test

[Qemu-devel] [PATCH] configure: change endian cross compilation test

[Stuart Yoder]

From: Stuart Yoder <stuart.yoder@freescale.com>

Previous check in configure's endian test was to determine if
this is a cross-compile build by testing whether --cross-prefix
was used.  This does not work for cross build environments
like Yocto that may set CC instead of --cross-prefix.

Instead, test whether host compiler is same as target compiler,
which also works when --cross-prefix is used.

Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
---
 configure |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/configure b/configure
index fe4fc4f..c5333bf 100755
--- a/configure
+++ b/configure
@@ -1269,7 +1269,7 @@ feature_not_found() {
   exit 1;
 }
 
-if test -z "$cross_prefix" ; then
+if test $cc = $host_cc; then
 
 # ---
 # big/little endian test
-- 
1.7.3.4

Re: [Qemu-devel] [PATCH] configure: change endian cross compilation test

[Paul Brook]

> From: Stuart Yoder <stuart.yoder@freescale.com>
> 
> Previous check in configure's endian test was to determine if
> this is a cross-compile build by testing whether --cross-prefix
> was used.  This does not work for cross build environments
> like Yocto that may set CC instead of --cross-prefix.
> 
> Instead, test whether host compiler is same as target compiler,
> which also works when --cross-prefix is used.

I'd much rather remove this test altogether.  If the cross case doesn't give 
the right answer for all the host systems we care about then we should fix 
that.

Paul

Re: [Qemu-devel] [PATCH] configure: change endian cross compilation test

[Peter Maydell]

2012/3/14 Paul Brook <paul@codesourcery.com>:
>> From: Stuart Yoder <stuart.yoder@freescale.com>
>>
>> Previous check in configure's endian test was to determine if
>> this is a cross-compile build by testing whether --cross-prefix
>> was used.  This does not work for cross build environments
>> like Yocto that may set CC instead of --cross-prefix.

Do we even support not using --cross-prefix ? I'd have expected just
setting CC to run into random problems like using the host arch's
version of strip rather than the cross toolchain, the host's
pkg-config rather than the one that knows where the cross libraries
are, etc etc.

>> Instead, test whether host compiler is same as target compiler,
>> which also works when --cross-prefix is used.
>
> I'd much rather remove this test altogether.  If the cross case doesn't give
> the right answer for all the host systems we care about then we should fix
> that.

Agreed. I think looking at the host CPUs we support the only ones
that aren't guaranteed either big or little endian are (a) mips
and (b) ARM. ARM already identifies big-endian by a compile-time
check, and it seems likely that MIPS could too.

-- PMM

Re: [Qemu-devel] [PATCH] configure: change endian cross compilation test

[Peter Maydell]

[added qemu-devel back again]

On 14 March 2012 17:51, Stuart Yoder <b08248@gmail.com> wrote:
> On Wed, Mar 14, 2012 at 12:17 PM, Peter Maydell
> <peter.maydell@linaro.org> wrote:
>> Agreed. I think looking at the host CPUs we support the only ones
>> that aren't guaranteed either big or little endian are (a) mips
>> and (b) ARM. ARM already identifies big-endian by a compile-time
>> check, and it seems likely that MIPS could too.
>
> So, you're proposing just leaving the test as:
>
> # if cross compiling, cannot launch a program, so make a static guess
> case "$cpu" in
>  arm)
>    # ARM can be either way; ask the compiler which one we are
>    if check_define __ARMEB__; then
>      bigendian=yes
>    fi
>  ;;
>  hppa|m68k|mips|mips64|ppc|ppc64|s390|s390x|sparc|sparc64)
>    bigendian=yes
>  ;;
> esac

No, I'm proposing that you find out what the right check_define
for mips is and make mips|mips64 have a similar case to the arm
one. Google suggests the answer is __MIPSEB__; you can do a quick
check by firing up the mipsel/mips images from
http://people.debian.org/~aurel32/qemu/ under qemu :-)

-- PMM

Re: [Qemu-devel] [PATCH] configure: change endian cross compilation test

[Stefan Weil]

Am 14.03.2012 19:09, schrieb Peter Maydell:
> [added qemu-devel back again]
>
> On 14 March 2012 17:51, Stuart Yoder<b08248@gmail.com>  wrote:
>> On Wed, Mar 14, 2012 at 12:17 PM, Peter Maydell
>> <peter.maydell@linaro.org>  wrote:
>>> Agreed. I think looking at the host CPUs we support the only ones
>>> that aren't guaranteed either big or little endian are (a) mips
>>> and (b) ARM. ARM already identifies big-endian by a compile-time
>>> check, and it seems likely that MIPS could too.
>> So, you're proposing just leaving the test as:
>>
>> # if cross compiling, cannot launch a program, so make a static guess
>> case "$cpu" in
>>   arm)
>>     # ARM can be either way; ask the compiler which one we are
>>     if check_define __ARMEB__; then
>>       bigendian=yes
>>     fi
>>   ;;
>>   hppa|m68k|mips|mips64|ppc|ppc64|s390|s390x|sparc|sparc64)
>>     bigendian=yes
>>   ;;
>> esac
> No, I'm proposing that you find out what the right check_define
> for mips is and make mips|mips64 have a similar case to the arm
> one. Google suggests the answer is __MIPSEB__; you can do a quick
> check by firing up the mipsel/mips images from
> http://people.debian.org/~aurel32/qemu/ under qemu :-)
>
> -- PMM

Running

     git grep "__MIPSEB__"

or

     git grep "__MIPSEL__"

would be a quicker check :-))

Stefan W.