CMake

From dankwiki
Revision as of 20:50, 2 August 2020 by Dank (talk | contribs) (→‎Debugging)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

CMake is one of the numerous build systems that seeks to replace Autotools+Make in the twenty-first century.

A CMake build can be configured on the command line with -D switches, or using ccmake/cmake-gui. Either way, the result is build infrastructure for some other tool, such as Make or Ninja.

Build Types

CMAKE_BUILD_TYPE can take any of the values in CMAKE_CONFIGURATION_TYPES. Important ones include:

  • Debug -- no optimization, full debug info, assert (NDEBUG is not defined)
  • RelWithDebInfo -- optimized, symbols
  • Release -- optimized, no symbols
  • MinSizeRel -- optimized for size

If CMAKE_BUILD_TYPE is not provided, none of these is used -- no debugging flags are set, and no optimization flags are set, in a somewhat stunning bit of unexpected behavior. The following snippet will ensure a default of RelWithDebInfo, and allow the value to be selected from a set in the gui:

set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
  set(CMAKE_BUILD_TYPE "RelWithDebInfo" CACHE STRING "Choose build mode." FORCE)
endif()
message(STATUS "Requested build mode: ${CMAKE_BUILD_TYPE}")

Build types can be added. I thought this might be useful for a Coverage target, but I ended up stuffing the coverage flags into CMAKE_C_FLAGS_DEBUG/CMAKE_CXX_FLAGS_DEBUG.

Debugging

Dump all current variables with:

get_cmake_property(_variableNames VARIABLES)
list (SORT _variableNames)
foreach (_variableName ${_variableNames})
    message(STATUS "${_variableName}=${${_variableName}}")
endforeach()

Better yet, include(CMakePrintHelpers) to get the useful commands cmake_print_properties() and cmake_print_variables().