[PATCH] Add configure check for _Static_assert()

[PATCH] Add configure check for _Static_assert()

[Thomas Petazzoni]

Commit 8efede20ef ("Use _Static_assert") introduced the usage of
_Static_assert(). However, _Static_assert() is a fairly new thing,
since it was introduced only in gcc 4.6. In order to support older
compilers, this patch adds a configure.in test that checks whether
_Static_assert() is usable or not, and adjust the behavior of the
assert_cc() macro accordingly.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 configure.ac    | 6 ++++++
 libkmod/macro.h | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/configure.ac b/configure.ac
index 40e54cf..cbe12f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -52,6 +52,12 @@ AC_CHECK_MEMBERS([struct stat.st_mtim], [], [], [#include <sys/stat.h>])
 # Check kernel headers
 AC_CHECK_HEADERS_ONCE([linux/module.h])
 
+AC_MSG_CHECKING([whether _Static_assert() is supported])
+AC_COMPILE_IFELSE(
+	[AC_LANG_SOURCE([[_Static_assert(1, "Test");]])],
+        [AC_DEFINE([HAVE_STATIC_ASSERT], [1], [Define is _Static_assert() is available])
+	 AC_MSG_RESULT([yes])],
+	[AC_MSG_RESULT([no])])
 
 #####################################################################
 # --with-
diff --git a/libkmod/macro.h b/libkmod/macro.h
index c6ba855..5992026 100644
--- a/libkmod/macro.h
+++ b/libkmod/macro.h
@@ -21,8 +21,12 @@
 
 #include <stddef.h>
 
+#if defined(HAVE_STATIC_ASSERT)
 #define assert_cc(expr) \
 	_Static_assert((expr), #expr)
+#else
+#define assert_cc(expr)
+#endif
 
 #if HAVE_TYPEOF
 #define check_types_match(expr1, expr2)		\
-- 
1.8.1.2

Re: [PATCH] Add configure check for _Static_assert()

[Lucas De Marchi]

Hi Thomas,

On Wed, Aug 28, 2013 at 12:33 PM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> Commit 8efede20ef ("Use _Static_assert") introduced the usage of
> _Static_assert(). However, _Static_assert() is a fairly new thing,
> since it was introduced only in gcc 4.6. In order to support older

What distro is still in gcc 4.6? Is it a LTS one?

> compilers, this patch adds a configure.in test that checks whether
> _Static_assert() is usable or not, and adjust the behavior of the
> assert_cc() macro accordingly.
>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>  configure.ac    | 6 ++++++
>  libkmod/macro.h | 4 ++++
>  2 files changed, 10 insertions(+)
>
> diff --git a/configure.ac b/configure.ac
> index 40e54cf..cbe12f3 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -52,6 +52,12 @@ AC_CHECK_MEMBERS([struct stat.st_mtim], [], [], [#include <sys/stat.h>])
>  # Check kernel headers
>  AC_CHECK_HEADERS_ONCE([linux/module.h])
>
> +AC_MSG_CHECKING([whether _Static_assert() is supported])
> +AC_COMPILE_IFELSE(
> +       [AC_LANG_SOURCE([[_Static_assert(1, "Test");]])],
> +        [AC_DEFINE([HAVE_STATIC_ASSERT], [1], [Define is _Static_assert() is available])
> +        AC_MSG_RESULT([yes])],
> +       [AC_MSG_RESULT([no])])
>
>  #####################################################################
>  # --with-
> diff --git a/libkmod/macro.h b/libkmod/macro.h
> index c6ba855..5992026 100644
> --- a/libkmod/macro.h
> +++ b/libkmod/macro.h
> @@ -21,8 +21,12 @@
>
>  #include <stddef.h>
>
> +#if defined(HAVE_STATIC_ASSERT)
>  #define assert_cc(expr) \
>         _Static_assert((expr), #expr)
> +#else
> +#define assert_cc(expr)

could you then define it similarly to what it was before then in this #else?

I think this would do it (totally untested) with the downside of an
ugly build error.

#define assert_cc(expr) \
       do { (void) sizeof(char [1 - 2*!(expr)]); } while(0)


thanks
Lucas De Marchi

Re: [PATCH] Add configure check for _Static_assert()

[Thomas Petazzoni]

Dear Lucas De Marchi,

On Thu, 29 Aug 2013 00:55:04 -0300, Lucas De Marchi wrote:
> Hi Thomas,
> 
> On Wed, Aug 28, 2013 at 12:33 PM, Thomas Petazzoni
> <thomas.petazzoni@free-electrons.com> wrote:
> > Commit 8efede20ef ("Use _Static_assert") introduced the usage of
> > _Static_assert(). However, _Static_assert() is a fairly new thing,
> > since it was introduced only in gcc 4.6. In order to support older
> 
> What distro is still in gcc 4.6? Is it a LTS one?

It's not a distro. As you know, I work on the Buildroot project, a tool
that builds rootfs for embedded Linux systems using cross-compilation.
One of the package we have is obviously kmod, but since we support a
wide range of architectures, not all of them are necessarily fully
up-to-date in terms of compiler version. The specific example that
raised the problem is a gcc 4.5.x toolchain for PowerPC provided by
Mentor Graphics Sourcery CodeBench (formerly known as CodeSourcery).

> > +#if defined(HAVE_STATIC_ASSERT)
> >  #define assert_cc(expr) \
> >         _Static_assert((expr), #expr)
> > +#else
> > +#define assert_cc(expr)
> 
> could you then define it similarly to what it was before then in this #else?
> 
> I think this would do it (totally untested) with the downside of an
> ugly build error.
> 
> #define assert_cc(expr) \
>        do { (void) sizeof(char [1 - 2*!(expr)]); } while(0)

Sure, will fix this and resend.

Thanks!

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Re: [PATCH] Add configure check for _Static_assert()

[Lucas De Marchi]

On Thu, Aug 29, 2013 at 4:49 AM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> Dear Lucas De Marchi,
>
> On Thu, 29 Aug 2013 00:55:04 -0300, Lucas De Marchi wrote:
>> Hi Thomas,
>>
>> On Wed, Aug 28, 2013 at 12:33 PM, Thomas Petazzoni
>> <thomas.petazzoni@free-electrons.com> wrote:
>> > Commit 8efede20ef ("Use _Static_assert") introduced the usage of
>> > _Static_assert(). However, _Static_assert() is a fairly new thing,
>> > since it was introduced only in gcc 4.6. In order to support older
>>
>> What distro is still in gcc 4.6? Is it a LTS one?
>
> It's not a distro. As you know, I work on the Buildroot project, a tool
> that builds rootfs for embedded Linux systems using cross-compilation.
> One of the package we have is obviously kmod, but since we support a
> wide range of architectures, not all of them are necessarily fully
> up-to-date in terms of compiler version. The specific example that
> raised the problem is a gcc 4.5.x toolchain for PowerPC provided by
> Mentor Graphics Sourcery CodeBench (formerly known as CodeSourcery).

ok

>
>> > +#if defined(HAVE_STATIC_ASSERT)
>> >  #define assert_cc(expr) \
>> >         _Static_assert((expr), #expr)
>> > +#else
>> > +#define assert_cc(expr)
>>
>> could you then define it similarly to what it was before then in this #else?
>>
>> I think this would do it (totally untested) with the downside of an
>> ugly build error.
>>
>> #define assert_cc(expr) \
>>        do { (void) sizeof(char [1 - 2*!(expr)]); } while(0)
>
> Sure, will fix this and resend.

ok

Lucas De Marchi

Re: [PATCH] Add configure check for _Static_assert()

[Lucas De Marchi]

On Thu, Aug 29, 2013 at 4:49 AM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> Dear Lucas De Marchi,
>
> On Thu, 29 Aug 2013 00:55:04 -0300, Lucas De Marchi wrote:
>> Hi Thomas,
>>
>> On Wed, Aug 28, 2013 at 12:33 PM, Thomas Petazzoni
>> <thomas.petazzoni@free-electrons.com> wrote:
>> > Commit 8efede20ef ("Use _Static_assert") introduced the usage of
>> > _Static_assert(). However, _Static_assert() is a fairly new thing,
>> > since it was introduced only in gcc 4.6. In order to support older
>>
>> What distro is still in gcc 4.6? Is it a LTS one?
>
> It's not a distro. As you know, I work on the Buildroot project, a tool
> that builds rootfs for embedded Linux systems using cross-compilation.
> One of the package we have is obviously kmod, but since we support a
> wide range of architectures, not all of them are necessarily fully
> up-to-date in terms of compiler version. The specific example that
> raised the problem is a gcc 4.5.x toolchain for PowerPC provided by
> Mentor Graphics Sourcery CodeBench (formerly known as CodeSourcery).
>
>> > +#if defined(HAVE_STATIC_ASSERT)
>> >  #define assert_cc(expr) \
>> >         _Static_assert((expr), #expr)
>> > +#else
>> > +#define assert_cc(expr)
>>
>> could you then define it similarly to what it was before then in this #else?
>>
>> I think this would do it (totally untested) with the downside of an
>> ugly build error.
>>
>> #define assert_cc(expr) \
>>        do { (void) sizeof(char [1 - 2*!(expr)]); } while(0)
>
> Sure, will fix this and resend.

Ping.

Lucas De Marchi