[CMake] question about version details in source code

[Eric Doenges]

Am 17.07.19 um 15:38 schrieb hex:
>
> hello community,
>
> I am receiving a|fatal error: foobar_version.h: No such file or 
> directory|for|foobar_version.h|. The reason is that the source file is 
> generated in|${CMAKE_CURRENT_BINARY_DIR}/foobar_version.cpp|while the 
> header file is in|${CMAKE_CURRENT_SOURCE_DIR}|as seen here:
>
> 1234|configure_file(foobar_version.cpp.in foobar_version.cpp @ONLY) # 
> configure_file(foobar_version.h foobar_version.h @ONLY) 
> add_library(foobar_version STATIC 
> ${CMAKE_CURRENT_BINARY_DIR}/foobar_version.cpp) |//
>
> In the source I simply|#include "foobar_version.h"|but the file is in 
> a different location.
>
> Why is this|CMakeLists.txt|file placing the files in different 
> locations? What should I do about it?
>
Nothing. You really want to keep source and build directories seperate, 
which means you do not want to generate files into the source directory. 
Instead, add the CMAKE_CURRENT_SOURCE_DIR to the include search path of 
any target that needs to include foobar_version.h using any one of:

1) the include_directories command
2) the target_include_directories command
3) the CMAKE_INCLUDE_CURRENT_DIR variable

> ------------------------------------------------------------------------
>
> also, what is the purpose of|mylib.cpp|, I had to create it otherwise 
> I receive:|No SOURCES given to target: fooToolkit|. The build is 
> successful but my file is currently empty. Here are all build steps:
>
> 123456789|configure_file(foobar_version.cpp.in foobar_version.cpp 
> @ONLY) configure_file(foobar_version.h foobar_version.h @ONLY) 
> add_library(foobar_version STATIC 
> ${CMAKE_CURRENT_BINARY_DIR}/foobar_version.cpp) add_executable(foobar 
> main.cpp) target_link_libraries(foobar PRIVATE foobar_version) 
> add_library(fooToolkit mylib.cpp) target_link_libraries(fooToolkit 
> PRIVATE foobar_version) |//
> ------------------------------------------------------------------------
I'm not sure what you are trying to accomplish with the fooToolkit 
target. If you want to create a library without sources for its 
properties (because you have a header-only library, for example), the 
correct way is to create an INTERFACE library, like so:

add_library(fooToolkit INTERFACE)

As a final note, I would strongly suggest you read the fine manual when 
you get errors from CMake - the documentation is actually pretty good 
when used as a reference and would have answered both of your questions.
-- 

*Dr. Eric Dönges *
Senior Software Engineer

MVTec Software GmbH | Arnulfstr. 205 | 80634 Munich | Germany
doenges at mvtec.com <mailto:doenges at mvtec.com> | Tel: +49 89 457 695-0 | 
www.mvtec.com <http://www.mvtec.com>

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