[CMake] Paths for targets to COMMAND in ADD_CUSTOM_COMMAND

[Jonas Karlsson]

On 25/03/2008, Jonas Karlsson <cj.karlsson at gmail.com> wrote:
> Hello,
>
First of all I must say I'm sorry that the message got sent twice.

>  I'm trying to build GTK-Qt-Engine 1.1, which use CMake as build system,
>  but it fails almost halfway through with the following message:
>  [ 44%] Generating ../../po/bg.gmo
>  /System/Links/Executables/msgfmt: error while opening "bg.po" for reading:
>  No such file or directory
>
After some more experimenting I've come to the conclusion that this might be
a bug because the inconsistant behaviour between build and install and if you
create your build directory as a subdirectory to the source or as a directory
somewhere else.

The following custom command and install macros are defined in a section
that loops over *.po files:

        ADD_CUSTOM_COMMAND(
                OUTPUT ${_out}
                COMMAND ${MSGFMT_EXECUTABLE} -o ${_out} ${_file}
                DEPENDS ${_file}
        )

        INSTALL(
                FILES ${_out}
                DESTINATION share/locale/${_file_we}/LC_MESSAGES/
                RENAME gtkqtengine.mo
        )

These rules generate the following build and install rules if cmake is
called in a
build directory as subdirectory to the sources:

../po/bg.gmo: ../po/bg.po
        $(CMAKE_COMMAND) -E cmake_progress_report
/Files/Compile/Sources/gtk-qt-engine/_build/CMakeFiles
$(CMAKE_PROGRESS_1)
        @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue
--bold "Generating ../../po/bg.gmo"
        cd /Files/Compile/Sources/gtk-qt-engine/_build/po &&
/System/Links/Executables/msgfmt -o bg.gmo bg.po

FILE(INSTALL DESTINATION
"${CMAKE_INSTALL_PREFIX}/share/locale/bg/LC_MESSAGES" TYPE FILE RENAME
"gtkqtengine.mo" COMPONENTS "Unspecified" FILES
"/Files/Compile/Sources/gtk-qt-engine/po/bg.gmo")

Notice that the cmake_echo_color command have relative path, "cd" before the
custom command has the build directory as target and the custom command
has no path prefix to the argument files. This while the install target has
absolute path to the file. Four different references...
It doesn't matter if I call cmake with relative or full path to the sources.

If I instead make a direcotry at the same level as the source directory (or
anywhere else besides inside the source directory) the following custom
command rule is generated:

../gtk-qt-engine/po/bg.gmo: ../gtk-qt-engine/po/bg.po
        $(CMAKE_COMMAND) -E cmake_progress_report
/Files/Compile/Sources/gtk-qt-engine-build/CMakeFiles
$(CMAKE_PROGRESS_1)
        @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue
--bold "Generating ../../gtk-qt-engine/po/bg.gmo"
        cd /Files/Compile/Sources/gtk-qt-engine-build/po &&
/System/Links/Executables/msgfmt -o bg.gmo bg.po

The difference here is that "cd" still has absolute path, but it changes to the
_source_ directory. The install rule is still the same.

Ultimately, as a build directory is recommended I'd like the command to put the
files defined as OUTPUT in the build directory. If cmake use "cd" to go to the
source directory and have relative/full path to build directory for
the output file or
if cmake stays in the build directory and reference the files defined as
DEPENDS with full/relative paths doesn't matter. I have also tried to use
"ARGS -o ${_out} ${_file}" to change the behaviour, but there was no difference.

I know people have recommended having build directory as subdirectory to the
source due to integration with the IDE works better, so shouldn't this work?

-- 
/Jonas