[cmake-developers] CMake strips MAKEFLAGS from environment

[Taylor Braun-Jones]

On Thu, May 21, 2015 at 8:56 AM, Brad King <brad.king at kitware.com> wrote:

> What are you trying to do?
>

I'm trying to implement a workaround solution for setting environment
variables in my Makefiles at build time. So what I started with was this:

  set(bullseye_environment COVFILE=${PROJECT_BINARY_DIR}/bullseye/test.cov)
  add_custom_target(coverage_data
    COMMAND env ${bullseye_environment}
      ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR} --clean-first
    COMMAND env ${bullseye_environment} ${CMAKE_CTEST_COMMAND}
--output-on-failure
    COMMENT "Generating test coverage data"
    VERBATIM
    )

Which works fine for Ninja generator. It works for Unix Makefiles too,
except that the parallelism is lost. I get errors like:

gmake[1]: warning: jobserver unavailable: using -j1.  Add `+' to parent
make rule.

So I added another workound for that:

  if(${CMAKE_GENERATOR} MATCHES ".* Makefiles$")
    set(environment_build_flags "$ENV{MAKEFLAGS}")
  endif()

  add_custom_target(coverage_data
    COMMAND env --unset=MAKEFLAGS ${bullseye_environment}
      ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR} --clean-first --
${environment_build_flags}
    COMMAND env ${bullseye_environment} ${CMAKE_CTEST_COMMAND}
--output-on-failure
    COMMENT "Generating test coverage data"
    VERBATIM
    )

Which allows the parallelism to work properly in an environment like:

export MAKEFLAGS=$(grep -i -c ^processor /proc/cpuinfo)
make coverage_data

Taylor
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