[CMake] Poor performance of copy_if_different

[Robert Dailey]

Thanks Clinton,

Here is what I have so far:


project( copy_dlls )

set( copycmd "${CMAKE_COMMAND}" ARGS "-E" "copy_if_different" )

set( configurations debug release )
foreach( config ${configurations} )
    string( TOUPPER ${config} upper_config )

    get_property( binarydirs GLOBAL PROPERTY THIRD_PARTY_DIRS_${upper_config} )
    foreach( dir ${binarydirs} )
        file( GLOB binaries "${dir}/*${CMAKE_SHARED_LIBRARY_SUFFIX}" )

        if( WIN32 AND config STREQUAL "debug" )
            file( GLOB pdbs "${dir}/*.pdb" )
            list( APPEND binaries ${pdbs} )
        endif()

        foreach( bin ${binaries} )
            get_filename_component( bin_file ${bin} NAME )

            list( APPEND bin_outputs ${bin} )
            list( APPEND copy_commands
                COMMAND ${copycmd} "${bin}"
"${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/${CMAKE_CFG_INTDIR}/${bin_file}"
            )
        endforeach()
    endforeach()

    add_custom_command(
        OUTPUT ${bin_outputs}
        ${copy_commands}
    )

    add_custom_target( copy_dlls_${config}
        COMMENT "Copying ${config} binaries..."
        DEPENDS ${bin_outputs}
    )
endforeach()


This doesn't seem to work though, CMake tells me:

CMake Error: Attempt to add a custom rule to output
"C:/Work/rdailey-hp/dpd-cmake/build-nmake-vc9/third_party/bdb/4.7.25/vc9sp1/debug/bin/libdb47d.dll.rule"
which already has a custom rule.

I'm trying to stuff all the copy commands and output files into 1
custom command, and wrap that with a custom target, so I can make
other targets depend on the custom target.

On Tue, Nov 6, 2012 at 11:44 AM, Clinton Stimpson <clinton at elemtech.com> wrote:
>
> add_custom_command(
>   OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/my.dll
>   COMMAND cmake -E copy ${CMAKE_CURRENT_SOURCE_DIR}/my.dll
> ${CMAKE_CURRENT_BINARY_DIR}/my.dll
>   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/my.dll
>   )
>
> add_custom_target(copy_dll ALL DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/my.dll)
>
> Whether you use 1 custom command per dll, or 1 for all dlls, is up to you.  If
> they usually change together, then you could have fewer custom commands.  In
> that case, the OUTPUT would have multiple files and both DEPENDS would have
> multiple files.
>
> Another alternative is to use add_custom_command(TARGET POST_BUILD ...) if
> these are dlls that you compile yourself and need to copy after the build
> step.
>
>
> On Tuesday, November 06, 2012 11:23:03 AM Robert Dailey wrote:
>> Also, is it safe to add 1 custom command for each DLL copy? Or would
>> you somehow only use 1 custom command and copy them all with it? Also
>> would I add the custom commands to the custom target?
>>
>> On Tue, Nov 6, 2012 at 11:11 AM, Clinton Stimpson <clinton at elemtech.com>
> wrote:
>> > On Tuesday, November 06, 2012 11:06:45 AM Robert Dailey wrote:
>> >> I use ${CMAKE_COMMAND} -E copy_if_different to copy DLL files to my
>> >> binary output directory. The custom target runs this command about
>> >> 50-100 times (for that many files).
>> >>
>> >> I notice that when all files are already copied, the commands still
>> >> run extremely slowly. It takes just as long to copy all the files as
>> >> it does to copy none of them.
>> >>
>> >> I used the Sysinternals tool called Process Monitor to see what CMake
>> >> is doing as it runs copy_if_different. It's opening the full file and
>> >> seems to be comparing actual contents instead of something simple,
>> >> such as timestamp.
>> >>
>> >> I do not need such a thorough check, I simply want the check to see
>> >> which timestamp is higher and copy if the source is newer than the
>> >> target.
>> >>
>> >> Any reason why copy_if_different is so slow? Is my assumption correct?
>> >> How can I make it faster?
>> >
>> > How about using plain "cmake -E copy ..." and rely on the timestamp check
>> > done by a custom command (add_custom_command()).
>> > You need to make sure the input/ouput parts of the custom command are set
>> > correctly so it can do a timestamp check.
>> >
>> > --
>> > Clinton Stimpson
>> > Elemental Technologies, Inc
>> > Computational Simulation Software, LLC
>> > www.csimsoft.com
>> > --
>> >
>> > Powered by www.kitware.com
>> >
>> > Visit other Kitware open-source projects at
>> > http://www.kitware.com/opensource/opensource.html
>> >
>> > Please keep messages on-topic and check the CMake FAQ at:
>> > http://www.cmake.org/Wiki/CMake_FAQ
>> >
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> --
> Clinton Stimpson
> Elemental Technologies, Inc
> Computational Simulation Software, LLC
> www.csimsoft.com
> --
>
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ
>
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