Re: [cmake-developers] FindPNG.cmake doesn't return a LIBRARY_DIR variable
Rolf Eike Beer wrote:
> First, FindPNG.cmake doesn't care about pkg-config files, if that is bug
Yes, I noticed that after I wrote the remark about the pkg-config files, and
didn't think to remove it (= I diagnosed the issue while writing the message).
> or feature depends on your personal things. CMake will detect the
> library using the full path (as it has done), and construct proper -L
> and -l from that. It doesn't happen here, which makes me suspect that
> you don't even link to ${PNG_LIBRARIES} or PNG::PNG (the latter being
>From the CMake file (digikam-5.6.0/core/app/CMakeLists.txt):
target_link_libraries(digikamcore
PUBLIC
Qt5::Core
Qt5::Gui
Qt5::Xml
Qt5::Widgets
Qt5::Sql
Qt5::WebKitWidgets
Qt5::PrintSupport
Qt5::Concurrent
KF5::Solid
KF5::WindowSystem
KF5::ConfigGui
KF5::CoreAddons
KF5::Service
KF5::XmlGui
KF5::I18n
# Required by CImg which use pthread internally.
${CMAKE_THREAD_LIBS_INIT}
${LCMS2_LIBRARIES} # filters
${TIFF_LIBRARIES}
${PNG_LIBRARIES}
${EXIV2_LIBRARIES}
libdng
libraw
)
> the better version). It seems to me like the -lpng you see comes from
> QtWebkitWidgets, which would also need to be linked against your library
It does and is, but I don't find a reference to libpng in its cmake modules
(nor
in any other of Qt5's modules, for that matter).
So while your hypothesis seems reasonable I don't see where the -lpng would be
added by Qt's modules. (FWIW, QtWebKit also has a .pc file, but it doesn't add -
lz after -lpng so unless someone reorders the link library order that file
cannot
be the source of the issue either.)
I've asked a more generic question about fully-qualified path conversion to
-lfoo
on the general ML ("/path/to/libpng.so automatic conversion to -lpng").
R.
--
Powered by www.kitware.com
Please keep messages on-topic and check the CMake FAQ at:
http://www.cmake.org/Wiki/CMake_FAQ
Kitware offers various services to support the CMake community. For more
information on each offering, please visit:
CMake Support: http://cmake.org/cmake/help/support.html
CMake Consulting: http://cmake.org/cmake/help/consulting.html
CMake Training Courses: http://cmake.org/cmake/help/training.html
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Follow this link to subscribe/unsubscribe:
http://public.kitware.com/mailman/listinfo/cmake-developers
Re: [cmake-developers] FindPNG.cmake doesn't return a LIBRARY_DIR variable
On Wed, Jul 12, 2017 at 14:22:40 +0200, Rolf Eike Beer wrote: > First, FindPNG.cmake doesn't care about pkg-config files, if that is bug > or feature depends on your personal things. CMake will detect the > library using the full path (as it has done), and construct proper -L > and -l from that. CMake prefers using full paths to libraries it finds, so I don't think it would turn a full path into a `-L` and `-l` flag pair. --Ben -- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: http://public.kitware.com/mailman/listinfo/cmake-developers
Re: [cmake-developers] FindPNG.cmake doesn't return a LIBRARY_DIR variable
Am 2017-07-12 13:35, schrieb René J.V. Bertin:
Hi,
I routinely use cmake to build projects for installation into a prefix
(/opt/local) and that use libraries from that location which also
exist in the system locations (typically in older versions, in that
case).
I thus have .pc files under /opt/local which generate linker
instructions of the type "-L/opt/local/lib -lfoo".
You'd expect this should work, but (too) often I still get linker
errors about symbols not being found which upon verification are in
fact provided by the intended library. In that case the
-L/opt/local/lib is typically given only once on the linker command
line ("way" before the corresponding -l argument), or not at all. See
the example below, where I don't see the -L option at all (linker
output and data from CMakeCache.txt after the HUGE linker command).
Initially I thought this was a case where one shouldn't filter out
identical -L options because the linker could limit their scope to
just the -l option immediately following the -L, but in this case it
appears that FindPNG.cmake simply doesn't consider the possibility
that libpng might be found in a location that isn't in the standard
library search path. IOW, FindPNG.cmake doesn't return a
PNG_LIBRARY_DIR variable, and provides the full path only in an
obsolete variable (PNG_LIBRARY). And for some reason, the command
`target_link_libraries(digikamcore ... ${PNG_LIBRARIES} ...)` is
translated into `-lpng -lz` .
Is that a bug or feature?
First, FindPNG.cmake doesn't care about pkg-config files, if that is bug
or feature depends on your personal things. CMake will detect the
library using the full path (as it has done), and construct proper -L
and -l from that. It doesn't happen here, which makes me suspect that
you don't even link to ${PNG_LIBRARIES} or PNG::PNG (the latter being
the better version). It seems to me like the -lpng you see comes from
QtWebkitWidgets, which would also need to be linked against your library
anyway, as things could break in funny ways otherwise (no idea how
stable the libPNG API is).
Eike
--
--
Powered by www.kitware.com
Please keep messages on-topic and check the CMake FAQ at:
http://www.cmake.org/Wiki/CMake_FAQ
Kitware offers various services to support the CMake community. For more
information on each offering, please visit:
CMake Support: http://cmake.org/cmake/help/support.html
CMake Consulting: http://cmake.org/cmake/help/consulting.html
CMake Training Courses: http://cmake.org/cmake/help/training.html
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Follow this link to subscribe/unsubscribe:
http://public.kitware.com/mailman/listinfo/cmake-developers
