[lttng-dev] [PATCH lttng-ust] Fix: Check g++ version before compiling 'hello.cxx' test

[Zifei Tong]

I've updated the patch addressing the problems mentioned earlier.

> Going forward, I think checking for the designated initializer feature
> via a small C++ testfile is more in line with the Autoconf philosophy.

> Moreover, the documentation and patches should take LLVM into account.

Tested on a Ububtu system with g++ 4.6, g++ 4.7 and clang++.

Fix: Check C++ designated initializers support before compiling 'hello.cxx' test

Fixes #557

Signed-off-by: Zifei Tong <soariez at gmail.com>
---
 README       |  3 ++-
 configure.ac | 15 ++++++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/README b/README
index 1f6b9d2..a2ff00b 100644
--- a/README
+++ b/README
@@ -111,7 +111,8 @@ USAGE:
   - Enable instrumentation and control tracing with the "lttng" command
     from lttng-tools. See lttng-tools doc/quickstart.txt.
   - Note for C++ support: since LTTng-UST 2.3, both tracepoints and
-    tracepoint probes can be compiled with g++.
+    tracepoint probes can be compiled in C++. To compile tracepoint probes
+    in C++, you need g++ >= 4.7 or Clang.


 ENVIRONMENT VARIABLES:
diff --git a/configure.ac b/configure.ac
index 802ccaa..0bc7992 100644
--- a/configure.ac
+++ b/configure.ac
@@ -83,8 +83,21 @@ AC_CACHE_CHECK([whether the C++ compiler works],
 		[rw_cv_prog_cxx_works],
 		[AC_LANG_PUSH([C++])
 		AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
-				[rw_cv_prog_cxx_works=yes],
+				[check_cxx_designated_initializers=yes],
 				[rw_cv_prog_cxx_works=no])
+		if test "$check_cxx_designated_initializers" = "yes"; then
+			AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+				struct foo { int a; int b; };
+				void fct(void)
+				{
+					struct foo f = {.a = 0, .b = 1};
+				}
+			]])],[
+				rw_cv_prog_cxx_works=yes
+			],[
+				rw_cv_prog_cxx_works=no
+			])
+		fi
 		AC_LANG_POP([C++])])

 AM_CONDITIONAL([CXX_WORKS], [test "x$rw_cv_prog_cxx_works" = "xyes"])
-- 
1.8.3.1

On 6/16/13, Mathieu Desnoyers <mathieu.desnoyers at efficios.com> wrote:
> * Christian Babeux (christian.babeux at efficios.com) wrote:
>> Hi Zifei,
>>
>> Checking specific version numbers might be a bit counterproductive
>> (e.g. what if some embedded platform as a GCC 4.7 with designated
>> initializer explicitly patched out?).
>>
>> Going forward, I think checking for the designated initializer feature
>> via a small C++ testfile is more in line with the Autoconf philosophy.
>> Also, we should conditionally disable the compilation of the
>> tracepoint probes requiring designated initializers if not supported.
>
> Moreover, the documentation and patches should take LLVM into account.
>
> Thanks,
>
> Mathieu
>
>>
>> Thanks,
>>
>> Christian
>>
>> On Sat, Jun 15, 2013 at 2:08 PM, Zifei Tong <soariez at gmail.com> wrote:
>> > Designated initializer support that is required to compile c++
>> > tracepoint probes is only available since g++ 4.7.
>> >
>> > Fixes #557
>> >
>> > Signed-off-by: Zifei Tong <soariez at gmail.com>
>> > ---
>> >  README       |  3 ++-
>> >  configure.ac | 16 ++++++++++++++--
>> >  2 files changed, 16 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/README b/README
>> > index 1f6b9d2..1c7a2f8 100644
>> > --- a/README
>> > +++ b/README
>> > @@ -111,7 +111,8 @@ USAGE:
>> >    - Enable instrumentation and control tracing with the "lttng"
>> > command
>> >      from lttng-tools. See lttng-tools doc/quickstart.txt.
>> >    - Note for C++ support: since LTTng-UST 2.3, both tracepoints and
>> > -    tracepoint probes can be compiled with g++.
>> > +    tracepoint probes can be compiled with g++. To compile tracepoint
>> > probes
>> > +    in g++, you need version 4.7 or above.
>> >
>> >
>> >  ENVIRONMENT VARIABLES:
>> > diff --git a/configure.ac b/configure.ac
>> > index 802ccaa..85a64a1 100644
>> > --- a/configure.ac
>> > +++ b/configure.ac
>> > @@ -83,9 +83,21 @@ AC_CACHE_CHECK([whether the C++ compiler works],
>> >                 [rw_cv_prog_cxx_works],
>> >                 [AC_LANG_PUSH([C++])
>> >                 AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
>> > -                               [rw_cv_prog_cxx_works=yes],
>> > +                               [check_gcc_cxx_version=yes],
>> >                                 [rw_cv_prog_cxx_works=no])
>> > -               AC_LANG_POP([C++])])
>> > +               AC_LANG_POP([C++])
>> > +               if test "$check_gcc_cxx_version" = "yes"; then
>> > +                       gcc_cxx_version=`$CXX -dumpversion`
>> > +                       gcc_cxx_major_version=$(echo $gcc_cxx_version |
>> > sed
>> > 's/^\([[0-9]]*\)\.[[0-9]]*.*$/\1/')
>> > +                       gcc_cxx_minor_version=$(echo $gcc_cxx_version |
>> > sed
>> > 's/^[[0-9]]*\.\([[0-9]]*\).*$/\1/')
>> > +                       if test "$gcc_cxx_major_version" -gt 4; then
>> > +                               rw_cv_prog_cxx_works="yes"
>> > +                       elif test "$gcc_cxx_major_version" -eq 4 -a
>> > "$gcc_cxx_minor_version" -ge 7; then
>> > +                               rw_cv_prog_cxx_works="yes"
>> > +                       else
>> > +                               rw_cv_prog_cxx_works="no"
>> > +                       fi
>> > +               fi])
>> >
>> >  AM_CONDITIONAL([CXX_WORKS], [test "x$rw_cv_prog_cxx_works" = "xyes"])
>> >
>> > --
>> > 1.8.3.1
>> >
>> > --
>> > Best Regards,
>> > 仝子飞 (Zifei Tong)
>> >
>> > _______________________________________________
>> > lttng-dev mailing list
>> > lttng-dev at lists.lttng.org
>> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>