[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Alexey Brodkin]

Some Qt sub-projects use pkg-config to recover compiler and linker
flags. Among other things include paths will be pulled in CFLAGS.

What's interesting Qt tries to play smart and convert include
paths from simple "-I" to "-isystem" if they match ones returned by [1]
---------------------------->8---------------------------
XXX/output/host/usr/bin/yyy-buildroot-linux-g++
--sysroot=XXX/output/host/usr/yyy-buildroot-linux/sysroot
-pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
-Os  -xc++ -E -v - < /dev/null
---------------------------->8---------------------------

Most probably that [2] was done to mute tons of warnings generated for
"system" headers. But commit message gives no hint here :(

So Qt's subprojects [and 3-rd party apps written on Qt] may end-up
having "-system ZZZ" in their Makefile. That's all right until an
application wants to use an STL header that includes for example
"stdlib.h" with gcc 6.x, see what happens then [3].

That fixes building of Qt5Webkit on ARM with gcc 6.x, see [4].

[1] http://code.qt.io/cgit/qt/qtbase.git/tree/configure?h=5.6.1#n3660
[2] http://code.qt.io/cgit/qt/qtbase.git/commit?id=0b144bc76a368ecc6c5c1121a1b51e888a0621ac
[3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129
[4] http://lists.busybox.net/pipermail/buildroot/2016-September/172666.html

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Seiderer <ps.report@gmx.net>
Cc: Julien Corjon <corjon.j@ecagroup.com>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
---
 package/qt5/qt5base/qt5base.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/package/qt5/qt5base/qt5base.mk b/package/qt5/qt5base/qt5base.mk
index bf541b0..2c52e2c 100644
--- a/package/qt5/qt5base/qt5base.mk
+++ b/package/qt5/qt5base/qt5base.mk
@@ -26,6 +26,7 @@ QT5BASE_CONFIGURE_OPTS += \
 	-system-zlib \
 	-system-pcre \
 	-no-pch \
+	-no-pkg-config \
 	-shared
 
 # Uses libgbm from mesa3d
-- 
2.7.4

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Yann E. MORIN]

Alexey, All,

On 2016-09-22 22:48 +0300, Alexey Brodkin spake thusly:
> Some Qt sub-projects use pkg-config to recover compiler and linker
> flags. Among other things include paths will be pulled in CFLAGS.
> 
> What's interesting Qt tries to play smart and convert include
> paths from simple "-I" to "-isystem" if they match ones returned by [1]
> ---------------------------->8---------------------------
> XXX/output/host/usr/bin/yyy-buildroot-linux-g++
> --sysroot=XXX/output/host/usr/yyy-buildroot-linux/sysroot
> -pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
> -Os  -xc++ -E -v - < /dev/null
> ---------------------------->8---------------------------
> 
> Most probably that [2] was done to mute tons of warnings generated for
> "system" headers. But commit message gives no hint here :(
> 
> So Qt's subprojects [and 3-rd party apps written on Qt] may end-up
> having "-system ZZZ" in their Makefile. That's all right until an
> application wants to use an STL header that includes for example
> "stdlib.h" with gcc 6.x, see what happens then [3].
> 
> That fixes building of Qt5Webkit on ARM with gcc 6.x, see [4].
> 
> [1] http://code.qt.io/cgit/qt/qtbase.git/tree/configure?h=5.6.1#n3660
> [2] http://code.qt.io/cgit/qt/qtbase.git/commit?id=0b144bc76a368ecc6c5c1121a1b51e888a0621ac
> [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129
> [4] http://lists.busybox.net/pipermail/buildroot/2016-September/172666.html
> 
> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: Peter Seiderer <ps.report@gmx.net>
> Cc: Julien Corjon <corjon.j@ecagroup.com>
> Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
> ---
>  package/qt5/qt5base/qt5base.mk | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/package/qt5/qt5base/qt5base.mk b/package/qt5/qt5base/qt5base.mk
> index bf541b0..2c52e2c 100644
> --- a/package/qt5/qt5base/qt5base.mk
> +++ b/package/qt5/qt5base/qt5base.mk
> @@ -26,6 +26,7 @@ QT5BASE_CONFIGURE_OPTS += \
>  	-system-zlib \
>  	-system-pcre \
>  	-no-pch \
> +	-no-pkg-config \

I have not paid much attention to the previous discussion on the topic.

However, I think disabling use of pkg-config is wrong. That is qmake
that is at fault here because, from what I understood from the previous
discussion, it emits -isystem where it should not.

So qmake needs to be fixed to not emit -isystem in those conditions.

Removing the use of pkg-config is just papering over the real problem.

Usually, using pkg-config solves more issues than not using it.

So, I am not very happy with this patch, to say the least... :-(

Yes, I undestand this is a complex issue. Yes, I understand it will be
hard to fix, and even if we can come up with something, it will be hard
to get something upstream that reverts this change.

At worst, let's see if we can at least try to revert that patch from
upstream and see if it fixes the issues.

Regards,
Yann E. MORIN.

>  	-shared
>  
>  # Uses libgbm from mesa3d
> -- 
> 2.7.4
> 

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Thomas Petazzoni]

Hello,

On Thu, 22 Sep 2016 22:58:17 +0200, Yann E. MORIN wrote:

> I have not paid much attention to the previous discussion on the topic.
> 
> However, I think disabling use of pkg-config is wrong. That is qmake
> that is at fault here because, from what I understood from the previous
> discussion, it emits -isystem where it should not.
> 
> So qmake needs to be fixed to not emit -isystem in those conditions.
> 
> Removing the use of pkg-config is just papering over the real problem.
> 
> Usually, using pkg-config solves more issues than not using it.
> 
> So, I am not very happy with this patch, to say the least... :-(

I entirely agree with Yann. Disabling pkg-config is clearly not the
solution we want to use.

Alexey, have you tried the other approaches I outlined in the thread
where the initial discussion took place?

Thanks,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Alexey Brodkin]

Hi Thomas, Yann,

On Fri, 2016-09-23 at 07:57 +0200, Thomas Petazzoni wrote:
> Hello,
> 
> On Thu, 22 Sep 2016 22:58:17 +0200, Yann E. MORIN wrote:
> 
> > 
> > I have not paid much attention to the previous discussion on the topic.
> > 
> > However, I think disabling use of pkg-config is wrong. That is qmake
> > that is at fault here because, from what I understood from the previous
> > discussion, it emits -isystem where it should not.
> > 
> > So qmake needs to be fixed to not emit -isystem in those conditions.
> > 
> > Removing the use of pkg-config is just papering over the real problem.
> > 
> > Usually, using pkg-config solves more issues than not using it.
> > 
> > So, I am not very happy with this patch, to say the least... :-(
> 
> I entirely agree with Yann. Disabling pkg-config is clearly not the
> solution we want to use.
>
> Alexey, have you tried the other approaches I outlined in the thread
> where the initial discussion took place?

Well I don't like removal of pkg-config usage either but...
Another approach with setting?QMAKE_CFLAGS_ISYSTEM to "" may work as well
(even thought I haven't tried it yet) but that will mean people using
buildroot-built toolchain for building their Qt5 apps will see those
compiler warnings about "wrong" stuff in system headers. In the end that's why
this "-isystem" was introduced in the first place.

In other words disabling pkg-config in Qt5 affects only Qt5 itself while
adding "QMAKE_CFLAGS_ISYSTEM = ''" to "package/qt5/qt5base/qmake.conf"
affects both Qt5 itself and apps that are written on Qt.

-Alexey

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Thomas Petazzoni]

Hello,

On Fri, 23 Sep 2016 06:12:44 +0000, Alexey Brodkin wrote:

> > Alexey, have you tried the other approaches I outlined in the thread
> > where the initial discussion took place?  
> 
> Well I don't like removal of pkg-config usage either but...
> Another approach with setting?QMAKE_CFLAGS_ISYSTEM to "" may work as well
> (even thought I haven't tried it yet) but that will mean people using
> buildroot-built toolchain for building their Qt5 apps will see those
> compiler warnings about "wrong" stuff in system headers. In the end that's why
> this "-isystem" was introduced in the first place.

Which warning will they see? I don't quite get why they would see a
warning, and still fail to understand why qmake uses -isystem.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Alexey Brodkin]

Hi Thomas,

On Fri, 2016-09-23 at 08:19 +0200, Thomas Petazzoni wrote:
> Hello,
> 
> On Fri, 23 Sep 2016 06:12:44 +0000, Alexey Brodkin wrote:
> 
> > 
> > > 
> > > Alexey, have you tried the other approaches I outlined in the thread
> > > where the initial discussion took place???
> > 
> > Well I don't like removal of pkg-config usage either but...
> > Another approach with setting?QMAKE_CFLAGS_ISYSTEM to "" may work as well
> > (even thought I haven't tried it yet) but that will mean people using
> > buildroot-built toolchain for building their Qt5 apps will see those
> > compiler warnings about "wrong" stuff in system headers. In the end that's why
> > this "-isystem" was introduced in the first place.
> 
> Which warning will they see? I don't quite get why they would see a
> warning,

I don't have an example handy but maybe this sheds some light on that
https://gcc.gnu.org/onlinedocs/cpp/System-Headers.h
tml?

> and still fail to understand why qmake uses -isystem.

Again I would assume that's to mute warnings that have nothing to
do with Qt itself or user's code.

-Alexey

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Alexey Brodkin]

Hi Thomas, Yann,

On Fri, 2016-09-23 at 10:28 +0300, Alexey Brodkin wrote:
> Hi Thomas,
> 
> On Fri, 2016-09-23 at 08:19 +0200, Thomas Petazzoni wrote:
> > 
> > Hello,
> > 
> > On Fri, 23 Sep 2016 06:12:44 +0000, Alexey Brodkin wrote:
> > 
> > > 
> > > 
> > > > 
> > > > 
> > > > Alexey, have you tried the other approaches I outlined in the thread
> > > > where the initial discussion took place???

Ok approach with setting empty QMAKE_CFLAGS_ISYSTEM works for me.

So what about something like that?
-------------------------->8---------------------
diff --git a/package/qt5/qt5base/qmake.conf b/package/qt5/qt5base/qmake.conf
index 2152d3c..49cf898 100644
--- a/package/qt5/qt5base/qmake.conf
+++ b/package/qt5/qt5base/qmake.conf
@@ -19,6 +19,7 @@ QMAKE_CXXFLAGS_RELEASE += -O3
?CONFIG?????????????????+= nostrip
?
?QMAKE_LIBS?????????????+= -lrt -lpthread -ldl
+QMAKE_CFLAGS_ISYSTEM???=
?
?include(../common/linux_device_post.conf)
?load(qt_config)
-------------------------->8---------------------

-Alexey

[Buildroot] [PATCH] qt5: Disable pkg-config usage for cross-building

[Fabián Inostroza]

Hi,

Got it working. I tough that the installation process was loading the
setuptools module from my system, because the files related to the
setuptools under the buildroot path were patched to include the additional
options, so I tried uninstalling python-setuptools from my system and now
it completes the build.

This must be a bug, what do you think?

PD: Alexey, sorry for the double mail.

2016-09-23 6:38 GMT-03:00 Alexey Brodkin <Alexey.Brodkin@synopsys.com>:

> Hi Thomas, Yann,
>
> On Fri, 2016-09-23 at 10:28 +0300, Alexey Brodkin wrote:
> > Hi Thomas,
> >
> > On Fri, 2016-09-23 at 08:19 +0200, Thomas Petazzoni wrote:
> > >
> > > Hello,
> > >
> > > On Fri, 23 Sep 2016 06:12:44 +0000, Alexey Brodkin wrote:
> > >
> > > >
> > > >
> > > > >
> > > > >
> > > > > Alexey, have you tried the other approaches I outlined in the
> thread
> > > > > where the initial discussion took place?
>
> Ok approach with setting empty QMAKE_CFLAGS_ISYSTEM works for me.
>
> So what about something like that?
> -------------------------->8---------------------
> diff --git a/package/qt5/qt5base/qmake.conf b/package/qt5/qt5base/qmake.
> conf
> index 2152d3c..49cf898 100644
> --- a/package/qt5/qt5base/qmake.conf
> +++ b/package/qt5/qt5base/qmake.conf
> @@ -19,6 +19,7 @@ QMAKE_CXXFLAGS_RELEASE += -O3
>  CONFIG                 += nostrip
>
>  QMAKE_LIBS             += -lrt -lpthread -ldl
> +QMAKE_CFLAGS_ISYSTEM   =
>
>  include(../common/linux_device_post.conf)
>  load(qt_config)
> -------------------------->8---------------------
>
> -Alexey
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
>
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