[CMake] How to rerun cmake if a file changes

[Eric Noulard]

2010/11/23 Vladislav Vaintroub <vvaintroub at googlemail.com>:
> Hello,
> we use a text file as input for out build to store version info.  The
> content of this file is
> ./VERSION:
>
> MYSQL_VERSION_MAJOR=5
> MYSQL_VERSION_MINOR=5
> MYSQL_VERSION_PATCH=8
> MYSQL_VERSION_EXTRA=
>
> During cmake run, the information is extracted, parsed,
> CPACK_PACKAGE_FILE_NAME is generated,  and some other things happen, e.g we
> configure a header file mysql_version.h.
> So far, it works nicely, the only problem  with it is that cmake is not
> rerun when this file changes. I made an attempt to fix it by introducing
> custom command and custom target
>
> ADD_CUSTOM_COMMAND(
>   OUTPUT  ${CMAKE_BINARY_DIR}/VERSION.dep
>   COMMAND ${CMAKE_COMMAND} ${CMAKE_BINARY_DIR}
>   COMMAND ${CMAKE_COMMAND} -E touch ${CMAKE_BINARY_DIR}/VERSION.dep
>   DEPENDS ${CMAKE_SOURCE_DIR}/VERSION
>   )
> ADD_CUSTOM_TARGET(check_version ALL DEPENDS ${CMAKE_BINARY_DIR}/VERSION.dep)
>
> This seems to work but is not without problems. For example the very first
> build with rerun cmake to generate VERSION.dep.  It takes some seconds with
> Makefiles,  this is not a big problem, however in Visual Studio (I'm using
> VS2010) the very first build would tell me "N  solutions regenerated, you
> want to rebuild?", and then  I clicking "OK" a COM error would popup (the
> build would actually still continue run successfully despite popups and COM
> error).
>
> So the question is if there is a nicer way to accomplish what I want to do.
> I'm aware that if VERSION had CMake syntax with SET(MYSQL_MAJOR_VERSION 5)
> etc, then I could just INCLUDE this file, and this would fix  problems I
> have.  I'm however more interested in a solution that would not force that
> file to be written in CMake syntax.

Do you want to preserve  the "content" of the file or you don't want
to write MYSQL_VERSION_xxx in CMake syntax?

If you only want to preserve this particular file you could generate
it file from your main CMakeLists.txt if you add
version definition in CMakeLists.txt:

SET(MYSQL_VERSION_MAJOR 5)
SET(MYSQL_VERSION_MINOR 5)
SET(MYSQL_VERSION_PATCH 8)
SET(MYSQL_VERSION_EXTRA "")

some VERSION.in file contains;
MYSQL_VERSION_MAJOR=@MYSQL_MAJOR_VERSION@
MYSQL_VERSION_MINOR=@MYSQL_VERSION_MINOR@
MYSQL_VERSION_PATCH=@MYSQL_VERSION_PATCH@
MYSQL_VERSION_EXTRA=@MYSQL_VERSION_EXTRA@


configure_file(${CMAKE_SOURCE_DIR}/VERSION.in
                    ${CMAKE_BINARY_DIR}/VERSION}
                    @ONLY)

if "VERSION" file has to be in source tree (would be better to avoid that):

configure_file(${CMAKE_SOURCE_DIR}/VERSION.in
                    ${CMAKE_SOURCE_DIR}/VERSION}
                    @ONLY)

If you don't want that you should already be generating
mysql_version.h using this file and may be some custom command/target
and I bet the rest of the build depends on mysql_version.h?

So may be your custom command used to generate mysql_version.h
is lacking a file dep?

By the way I cannot find any VERSION file on a fresh update of lp:mysql-server ?

-- 
Erk
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