ceres-solver/cmake/AddCompileFlagsIfSupported.cmake

# Ceres Solver - A fast non-linear least squares minimizer
# Copyright 2017 Google Inc. All rights reserved.
# http://ceres-solver.org/
#
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# Author: sergey.vfx@gmail.com (Sergey Sharybin)

function(add_cxx_compiler_flag_if_supported
    AGGREGATED_CXX_FLAGS_VAR
    FLAG_TO_ADD_IF_SUPPORTED)
  include(CheckCXXCompilerFlag)
  # Use of whitespace or '-' in variable names (used by CheckCXXSourceCompiles
  # as #defines) will trigger errors.
  string(STRIP "${FLAG_TO_ADD_IF_SUPPORTED}" FLAG_TO_ADD_IF_SUPPORTED)
  # Build an informatively named test result variable so that it will be evident
  # which tests were performed/succeeded in the CMake output, e.g for -Wall:
  #
  # -- Performing Test CHECK_CXX_FLAG_Wall - Success
  #
  # NOTE: This variable is also used to cache test result.
  string(REPLACE "-" "_" CHECK_CXX_FLAG
    "CHECK_CXX_FLAG${FLAG_TO_ADD_IF_SUPPORTED}")
  check_cxx_compiler_flag(${FLAG_TO_ADD_IF_SUPPORTED} ${CHECK_CXX_FLAG})
  if (${CHECK_CXX_FLAG})
    set(${AGGREGATED_CXX_FLAGS_VAR}
      "${${AGGREGATED_CXX_FLAGS_VAR}} ${FLAG_TO_ADD_IF_SUPPORTED}" PARENT_SCOPE)
  endif()
endfunction()