[CMake] Check whether C++ headers are self-sufficient

[Robert Maynard]

I have worked on projects where we do something fairly similar. The
significant difference is that we create only a single executable per
directory. All told is it a fairly simple and looks something like:

# Builds a source file and an executable that does nothing other than
# compile the given header files.
function(add_header_test name)
  set(hfiles ${ARGN})
  set(suffix ".cpp")
  set(cxxfiles)
  foreach (header ${ARGN})
    string(REPLACE "${CMAKE_CURRENT_BINARY_DIR}" "" header "${header}")
    get_filename_component(headername ${header} NAME_WE)
    set(src
${CMAKE_CURRENT_BINARY_DIR}/TestBuild_${name}_${headername}${suffix})
    configure_file(${SMTK_SOURCE_DIR}/CMake/TestBuild.cxx.in ${src} @ONLY)
    set(cxxfiles ${cxxfiles} ${src})
  endforeach (header)

  add_library(TestBuild_${name} ${cxxfiles} ${hfiles})
  target_include_directories(TestBuild_${name} ${CMAKE_CURRENT_BINARY_DIR})
  set_source_files_properties(${hfiles} PROPERTIES HEADER_FILE_ONLY TRUE)
endfunction(add_header_test)

On Sat, Mar 14, 2015 at 8:19 AM, Christoph Grüninger <foss at grueninger.de>
wrote:

> Dear CMakers,
> I want to have all my C++ headers self-sufficient (self-contained),
> i.e., a header can be included without additional includes. This is not
> only handy but also part of Google's C++ styleguide [2].
>
> It would be great to have a make target (let's call it headercheck),
> that can check for this, by compiling a simple test.cc file for each
> current_header.h:
>   #include <config.h>
>   #include "current_header.h"
>   #include "current_header.h"
>
> Additionally it would be great to have such a target for every folder
> (checking all headers recursively) and every header that is explicitly
> passed as an argument.
>
> We tried this with CMake: We generate a test.cc file per header and
> create a library for every cc file. The problem is, that we get hundreds
> of additional targets, we generate a lot of folders and files which can
> increase our build directory size by an order of magnitude and it does
> not work properly on a per file or per directory basis.
>
> What do you think, is there a good way to have such a target headercheck
> with CMake? Or would it be better to include it as a CTest? Or better as
> an external (bash) script as proposed in [1]?
>
> If it can be done in a good way with CMake, would it be of interest to
> include it as a feature in CMake? Or as an external project similar to
> UseLATEX.cmake?
>
> Bye
> Christoph
>
> [1]
>
> http://stackoverflow.com/questions/1892043/self-sufficient-header-files-in-c-c
> [2]
>
> http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Self_contained_Headers
>
> --
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> you beat cancer by how you live, why you live, and in the
> manner in which you live.      -- Stuart Scott, 1965-2015
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