[Qemu-devel] [PATCH 0/2] configure: clang 3.5.0 build fixes

[Qemu-devel] [PATCH 0/2] configure: clang 3.5.0 build fixes

[Stefan Hajnoczi]

QEMU does not compile cleanly under clang 3.5.0.  These patches eliminate the
avalanche of warnings and make the build usable.

Stefan Hajnoczi (2):
  configure: handle clang -nopie argument warning
  configure: silence glib unknown attribute __alloc_size__

 configure | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

-- 
2.1.0

[Qemu-devel] [PATCH 1/2] configure: handle clang -nopie argument warning

[Stefan Hajnoczi]

gcc 4.9.2 treats -nopie as an error:

  cc: error: unrecognized command line option ‘-nopie’

clang 3.5.0 treats -nopie as a warning:

  clang: warning: argument unused during compilation: '-nopie'

The causes ./configure to fail with clang:

  ERROR: configure test passed without -Werror but failed with -Werror.

Make the -nopie test use -Werror so that compile_prog works for both gcc
and clang.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 configure | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure b/configure
index 7ba4bcb..4f9f689 100755
--- a/configure
+++ b/configure
@@ -1589,7 +1589,7 @@ EOF
     fi
   fi
 
-  if compile_prog "-fno-pie" "-nopie"; then
+  if compile_prog "-Werror -fno-pie" "-nopie"; then
     CFLAGS_NOPIE="-fno-pie"
     LDFLAGS_NOPIE="-nopie"
   fi
-- 
2.1.0

Re: [Qemu-devel] [PATCH 1/2] configure: handle clang -nopie argument warning

[John Snow]

On 03/10/2015 08:23 AM, Stefan Hajnoczi wrote:
> gcc 4.9.2 treats -nopie as an error:
>
>    cc: error: unrecognized command line option ‘-nopie’
>
> clang 3.5.0 treats -nopie as a warning:
>
>    clang: warning: argument unused during compilation: '-nopie'
>
> The causes ./configure to fail with clang:
>
>    ERROR: configure test passed without -Werror but failed with -Werror.
>
> Make the -nopie test use -Werror so that compile_prog works for both gcc
> and clang.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   configure | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/configure b/configure
> index 7ba4bcb..4f9f689 100755
> --- a/configure
> +++ b/configure
> @@ -1589,7 +1589,7 @@ EOF
>       fi
>     fi
>
> -  if compile_prog "-fno-pie" "-nopie"; then
> +  if compile_prog "-Werror -fno-pie" "-nopie"; then
>       CFLAGS_NOPIE="-fno-pie"
>       LDFLAGS_NOPIE="-nopie"
>     fi
>

Oh, clang doesn't support -nopie but doesn't fail, so we have to force 
it to in order to get proper configuration.

Makes sense.

Reviewed-by: John Snow <jsnow@redhat.com>

[Qemu-devel] [PATCH 2/2] configure: silence glib unknown attribute __alloc_size__

[Stefan Hajnoczi]

The glib headers use GCC attributes.  Unfortunately the __GNUC__ and
__GNUC_MINOR__ version macros are also defined by clang, but clang
doesn't support the same attributes as GCC.

clang 3.5.0 does not support the __alloc_size__ attribute:

  https://github.com/llvm-mirror/clang/commit/c047507a9a79e89fc8339e074fa72822a7e7ea73

The following warning is produced:

  gstrfuncs.h:257:44: warning: unknown attribute '__alloc_size__' ignored [-Wunknown-attributes]
      G_GNUC_MALLOC G_GNUC_ALLOC_SIZE(2);
  gmacros.h:67:45: note: expanded from macro 'G_GNUC_ALLOC_SIZE'
      #define G_GNUC_ALLOC_SIZE(x) __attribute__((__alloc_size__(x)))

This patch checks whether glib headers cause warnings and disables
-Wunknown-attributes if that is the case.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 configure | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/configure b/configure
index 4f9f689..00740ad 100755
--- a/configure
+++ b/configure
@@ -2773,6 +2773,16 @@ if ! $pkg_config --atleast-version=2.38 glib-2.0; then
     glib_subprocess=no
 fi
 
+# Silence clang 3.5.0 warnings about glib attribute __alloc_size__ usage
+cat > $TMPC << EOF
+#include <glib.h>
+int main(void) { return 0; }
+EOF
+if ! compile_prog "-Werror" "" ; then
+  glib_cflags="-Wno-unknown-attributes $glib_cflags"
+  CFLAGS="-Wno-unknown-attributes $CFLAGS"
+fi
+
 ##########################################
 # SHA command probe for modules
 if test "$modules" = yes; then
-- 
2.1.0

Re: [Qemu-devel] [PATCH 2/2] configure: silence glib unknown attribute __alloc_size__

[John Snow]

On 03/10/2015 08:23 AM, Stefan Hajnoczi wrote:
> The glib headers use GCC attributes.  Unfortunately the __GNUC__ and
> __GNUC_MINOR__ version macros are also defined by clang, but clang
> doesn't support the same attributes as GCC.
>
> clang 3.5.0 does not support the __alloc_size__ attribute:
>
>    https://github.com/llvm-mirror/clang/commit/c047507a9a79e89fc8339e074fa72822a7e7ea73
>
> The following warning is produced:
>
>    gstrfuncs.h:257:44: warning: unknown attribute '__alloc_size__' ignored [-Wunknown-attributes]
>        G_GNUC_MALLOC G_GNUC_ALLOC_SIZE(2);
>    gmacros.h:67:45: note: expanded from macro 'G_GNUC_ALLOC_SIZE'
>        #define G_GNUC_ALLOC_SIZE(x) __attribute__((__alloc_size__(x)))
>
> This patch checks whether glib headers cause warnings and disables
> -Wunknown-attributes if that is the case.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   configure | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/configure b/configure
> index 4f9f689..00740ad 100755
> --- a/configure
> +++ b/configure
> @@ -2773,6 +2773,16 @@ if ! $pkg_config --atleast-version=2.38 glib-2.0; then
>       glib_subprocess=no
>   fi
>
> +# Silence clang 3.5.0 warnings about glib attribute __alloc_size__ usage
> +cat > $TMPC << EOF
> +#include <glib.h>
> +int main(void) { return 0; }
> +EOF
> +if ! compile_prog "-Werror" "" ; then
> +  glib_cflags="-Wno-unknown-attributes $glib_cflags"
> +  CFLAGS="-Wno-unknown-attributes $CFLAGS"
> +fi
> +
>   ##########################################
>   # SHA command probe for modules
>   if test "$modules" = yes; then
>

Reviewed-by: John Snow <jsnow@redhat.com>

Re: [Qemu-devel] [PATCH 0/2] configure: clang 3.5.0 build fixes

[Stefan Hajnoczi]

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On Tue, Mar 10, 2015 at 12:23:43PM +0000, Stefan Hajnoczi wrote:
> QEMU does not compile cleanly under clang 3.5.0.  These patches eliminate the
> avalanche of warnings and make the build usable.
> 
> Stefan Hajnoczi (2):
>   configure: handle clang -nopie argument warning
>   configure: silence glib unknown attribute __alloc_size__
> 
>  configure | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> -- 
> 2.1.0
> 
> 

Thanks, applied to my net tree:
https://github.com/stefanha/qemu/commits/net

Stefan

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