[v1] configure: Make "does libgio work" test pull in some actual functions

[PATCH for-5.2] configure: Make "does libgio work" test pull in some actual functions

Posted by Peter Maydell 3 years, 5 months ago

In commit 76346b6264a9b01979 we tried to add a configure check that
the libgio pkg-config data was correct, which builds an executable
linked against it.  Unfortunately this doesn't catch the problem
(missing static library dependency info), because a "do nothing" test
source file doesn't have any symbol references that cause the linker
to pull in .o files from libgio.a, and so we don't see the "missing
symbols from libmount" error that a full QEMU link triggers.

(The ineffective test went unnoticed because of a typo that
effectively disabled libgio unconditionally, but after commit
3569a5dfc11f2 fixed that, a static link of the system emulator on
Ubuntu stopped working again.)

Improve the gio test by having the test source fragment reference a
g_dbus function (which is what is indirectly causing us to end up
wanting functions from libmount).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
The ideal thing here might perhaps be to force the linker to
pull in everything in the library rather than trusting that
this particular function is sufficient to trigger the need
for libmount functions, but annoyingly gcc and clang
have different command line options to do that.

 configure | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 4cef321d9dc..2717cf1db0a 100755
--- a/configure
+++ b/configure
@@ -3512,8 +3512,15 @@ if $pkg_config --atleast-version=$glib_req_ver gio-2.0; then
     # Check that the libraries actually work -- Ubuntu 18.04 ships
     # with pkg-config --static --libs data for gio-2.0 that is missing
     # -lblkid and will give a link error.
-    write_c_skeleton
-    if compile_prog "" "$gio_libs" ; then
+    cat > $TMPC <<EOF
+#include <gio/gio.h>
+int main(void)
+{
+    g_dbus_proxy_new_sync(0, 0, 0, 0, 0, 0, 0, 0);
+    return 0;
+}
+EOF
+    if compile_prog "$gio_cflags" "$gio_libs" ; then
         gio=yes
     else
         gio=no
-- 
2.20.1

Re: [PATCH for-5.2] configure: Make "does libgio work" test pull in some actual functions

Posted by Paolo Bonzini 3 years, 5 months ago

On 16/11/20 11:46, Peter Maydell wrote:
> In commit 76346b6264a9b01979 we tried to add a configure check that
> the libgio pkg-config data was correct, which builds an executable
> linked against it.  Unfortunately this doesn't catch the problem
> (missing static library dependency info), because a "do nothing" test
> source file doesn't have any symbol references that cause the linker
> to pull in .o files from libgio.a, and so we don't see the "missing
> symbols from libmount" error that a full QEMU link triggers.
> 
> (The ineffective test went unnoticed because of a typo that
> effectively disabled libgio unconditionally, but after commit
> 3569a5dfc11f2 fixed that, a static link of the system emulator on
> Ubuntu stopped working again.)
> 
> Improve the gio test by having the test source fragment reference a
> g_dbus function (which is what is indirectly causing us to end up
> wanting functions from libmount).
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> The ideal thing here might perhaps be to force the linker to
> pull in everything in the library rather than trusting that
> this particular function is sufficient to trigger the need
> for libmount functions, but annoyingly gcc and clang
> have different command line options to do that.
> 
>   configure | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/configure b/configure
> index 4cef321d9dc..2717cf1db0a 100755
> --- a/configure
> +++ b/configure
> @@ -3512,8 +3512,15 @@ if $pkg_config --atleast-version=$glib_req_ver gio-2.0; then
>       # Check that the libraries actually work -- Ubuntu 18.04 ships
>       # with pkg-config --static --libs data for gio-2.0 that is missing
>       # -lblkid and will give a link error.
> -    write_c_skeleton
> -    if compile_prog "" "$gio_libs" ; then
> +    cat > $TMPC <<EOF
> +#include <gio/gio.h>
> +int main(void)
> +{
> +    g_dbus_proxy_new_sync(0, 0, 0, 0, 0, 0, 0, 0);
> +    return 0;
> +}
> +EOF
> +    if compile_prog "$gio_cflags" "$gio_libs" ; then
>           gio=yes
>       else
>           gio=no
> 

Looks good,

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo

Re: [PATCH for-5.2] configure: Make "does libgio work" test pull in some actual functions

Posted by Peter Maydell 3 years, 5 months ago

On Mon, 16 Nov 2020 at 18:25, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 16/11/20 11:46, Peter Maydell wrote:
> > In commit 76346b6264a9b01979 we tried to add a configure check that
> > the libgio pkg-config data was correct, which builds an executable
> > linked against it.  Unfortunately this doesn't catch the problem
> > (missing static library dependency info), because a "do nothing" test
> > source file doesn't have any symbol references that cause the linker
> > to pull in .o files from libgio.a, and so we don't see the "missing
> > symbols from libmount" error that a full QEMU link triggers.
> >
> > (The ineffective test went unnoticed because of a typo that
> > effectively disabled libgio unconditionally, but after commit
> > 3569a5dfc11f2 fixed that, a static link of the system emulator on
> > Ubuntu stopped working again.)
> >
> > Improve the gio test by having the test source fragment reference a
> > g_dbus function (which is what is indirectly causing us to end up
> > wanting functions from libmount).
> >
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > ---
> > The ideal thing here might perhaps be to force the linker to
> > pull in everything in the library rather than trusting that
> > this particular function is sufficient to trigger the need
> > for libmount functions, but annoyingly gcc and clang
> > have different command line options to do that.
> >
> >   configure | 11 +++++++++--
> >   1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/configure b/configure
> > index 4cef321d9dc..2717cf1db0a 100755
> > --- a/configure
> > +++ b/configure
> > @@ -3512,8 +3512,15 @@ if $pkg_config --atleast-version=$glib_req_ver gio-2.0; then
> >       # Check that the libraries actually work -- Ubuntu 18.04 ships
> >       # with pkg-config --static --libs data for gio-2.0 that is missing
> >       # -lblkid and will give a link error.
> > -    write_c_skeleton
> > -    if compile_prog "" "$gio_libs" ; then
> > +    cat > $TMPC <<EOF
> > +#include <gio/gio.h>
> > +int main(void)
> > +{
> > +    g_dbus_proxy_new_sync(0, 0, 0, 0, 0, 0, 0, 0);
> > +    return 0;
> > +}
> > +EOF
> > +    if compile_prog "$gio_cflags" "$gio_libs" ; then
> >           gio=yes
> >       else
> >           gio=no
> >
>
> Looks good,
>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks; applied to target-arm.next for 5.2.

-- PMM