[Qemu-devel] [PATCH] configure: check that C++ compiler actually works

[Qemu-devel] [PATCH] configure: check that C++ compiler actually works

[Peter Maydell]

Check that the C++ compiler works with the C compiler; if it
does not, then don't pass CXX to the build process. This
fixes a regression where QEMU was no longer building if the
build environment didn't have a C++ compiler (introduced
in commit 3144f78b, which incorrectly assumed that rules.mak
would only see a non-empty $(CXX) if configure had actually
found a working C++ compiler).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com>
---
Apologies for the breakage for people who were building in
setups with no C++ compiler -- I should have tested the
original change more thoroughly.

 configure | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/configure b/configure
index 4648117..6829cbb 100755
--- a/configure
+++ b/configure
@@ -1289,6 +1289,35 @@ else
     error_exit "\"$cc\" either does not exist or does not work"
 fi
 
+# Check that the C++ compiler exists and works with the C compiler
+if has $cxx; then
+    cat > $TMPC <<EOF
+int c_function(void);
+int main(void) { return c_function(); }
+EOF
+
+    compile_object
+
+    cat > $TMPC <<EOF
+extern "C" {
+   int c_function(void);
+}
+int c_function(void) { return 42; }
+EOF
+
+    if (cc=$cxx do_cc $QEMU_CFLAGS -o $TMPE $TMPC $TMPO $LDFLAGS); then
+        # C++ compiler $cxx works ok with C compiler $cc
+        :
+    else
+        echo "C++ compiler $cxx does not work with C compiler $cc"
+        echo "Disabling C++ specific optional code"
+        cxx=
+    fi
+else
+    echo "No C++ compiler available; disabling C++ specific optional code"
+    cxx=
+fi
+
 # Consult white-list to determine whether to enable werror
 # by default.  Only enable by default for git builds
 z_version=`cut -f3 -d. $source_path/VERSION`
-- 
1.8.5

Re: [Qemu-devel] [PATCH] configure: check that C++ compiler actually works

[Thomas Huth]

On Thu, 20 Feb 2014 15:10:16 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:

> Check that the C++ compiler works with the C compiler; if it
> does not, then don't pass CXX to the build process. This
> fixes a regression where QEMU was no longer building if the
> build environment didn't have a C++ compiler (introduced
> in commit 3144f78b, which incorrectly assumed that rules.mak
> would only see a non-empty $(CXX) if configure had actually
> found a working C++ compiler).
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com>
> ---
> Apologies for the breakage for people who were building in
> setups with no C++ compiler -- I should have tested the
> original change more thoroughly.
> 
>  configure | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/configure b/configure
> index 4648117..6829cbb 100755
> --- a/configure
> +++ b/configure
> @@ -1289,6 +1289,35 @@ else
>      error_exit "\"$cc\" either does not exist or does not work"
>  fi
> 
> +# Check that the C++ compiler exists and works with the C compiler
> +if has $cxx; then
> +    cat > $TMPC <<EOF
> +int c_function(void);
> +int main(void) { return c_function(); }
> +EOF
> +
> +    compile_object
> +
> +    cat > $TMPC <<EOF
> +extern "C" {
> +   int c_function(void);
> +}
> +int c_function(void) { return 42; }
> +EOF
> +
> +    if (cc=$cxx do_cc $QEMU_CFLAGS -o $TMPE $TMPC $TMPO $LDFLAGS); then
> +        # C++ compiler $cxx works ok with C compiler $cc
> +        :
> +    else
> +        echo "C++ compiler $cxx does not work with C compiler $cc"
> +        echo "Disabling C++ specific optional code"
> +        cxx=
> +    fi
> +else
> +    echo "No C++ compiler available; disabling C++ specific optional code"
> +    cxx=
> +fi
> +
>  # Consult white-list to determine whether to enable werror
>  # by default.  Only enable by default for git builds
>  z_version=`cut -f3 -d. $source_path/VERSION`

Works fine for me now on my system w/o C++ compiler:
Tested-by: Thomas Huth <thuth@linux.vnet.ibm.com>

Re: [Qemu-devel] [PATCH] configure: check that C++ compiler actually works

[Alexey Kardashevskiy]

On 02/21/2014 02:58 AM, Thomas Huth wrote:
> On Thu, 20 Feb 2014 15:10:16 +0000
> Peter Maydell <peter.maydell@linaro.org> wrote:
> 
>> Check that the C++ compiler works with the C compiler; if it
>> does not, then don't pass CXX to the build process. This
>> fixes a regression where QEMU was no longer building if the
>> build environment didn't have a C++ compiler (introduced
>> in commit 3144f78b, which incorrectly assumed that rules.mak
>> would only see a non-empty $(CXX) if configure had actually
>> found a working C++ compiler).
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com>
>> ---
>> Apologies for the breakage for people who were building in
>> setups with no C++ compiler -- I should have tested the
>> original change more thoroughly.
>>
>>  configure | 29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/configure b/configure
>> index 4648117..6829cbb 100755
>> --- a/configure
>> +++ b/configure
>> @@ -1289,6 +1289,35 @@ else
>>      error_exit "\"$cc\" either does not exist or does not work"
>>  fi
>>
>> +# Check that the C++ compiler exists and works with the C compiler
>> +if has $cxx; then
>> +    cat > $TMPC <<EOF
>> +int c_function(void);
>> +int main(void) { return c_function(); }
>> +EOF
>> +
>> +    compile_object
>> +
>> +    cat > $TMPC <<EOF
>> +extern "C" {
>> +   int c_function(void);
>> +}
>> +int c_function(void) { return 42; }
>> +EOF
>> +
>> +    if (cc=$cxx do_cc $QEMU_CFLAGS -o $TMPE $TMPC $TMPO $LDFLAGS); then
>> +        # C++ compiler $cxx works ok with C compiler $cc
>> +        :
>> +    else
>> +        echo "C++ compiler $cxx does not work with C compiler $cc"
>> +        echo "Disabling C++ specific optional code"
>> +        cxx=
>> +    fi
>> +else
>> +    echo "No C++ compiler available; disabling C++ specific optional code"
>> +    cxx=
>> +fi
>> +
>>  # Consult white-list to determine whether to enable werror
>>  # by default.  Only enable by default for git builds
>>  z_version=`cut -f3 -d. $source_path/VERSION`
> 
> Works fine for me now on my system w/o C++ compiler:
> Tested-by: Thomas Huth <thuth@linux.vnet.ibm.com>


Works for me too, in cross environment for ppc64 on x86_64,
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Thanks.


-- 
Alexey

Re: [Qemu-devel] [PATCH] configure: check that C++ compiler actually works

[Peter Maydell]

On 20 February 2014 15:10, Peter Maydell <peter.maydell@linaro.org> wrote:
> Check that the C++ compiler works with the C compiler; if it
> does not, then don't pass CXX to the build process. This
> fixes a regression where QEMU was no longer building if the
> build environment didn't have a C++ compiler (introduced
> in commit 3144f78b, which incorrectly assumed that rules.mak
> would only see a non-empty $(CXX) if configure had actually
> found a working C++ compiler).
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Reported-by: Thomas Huth <thuth@linux.vnet.ibm.com>
> ---
> Apologies for the breakage for people who were building in
> setups with no C++ compiler -- I should have tested the
> original change more thoroughly

Applied directly to master since it's a build-breakage fix.

thanks
-- PMM