[Cmake][feature] allow overloading of compiler flags on the command line via a compiler

script. This feature is disabled by default and can be enabled by
-DALLOW_CXXFLAGS_OVERWRITE=ON.

cmake/modules/DuneMacros.cmake

@@ -80,6 +80,7 @@ enable_language(C) # Enable C to skip CXX bindings for some tests.
 
 include(FeatureSummary)
 include(DuneEnableAllPackages)
+include(OverloadCompilerFlags)
 
 include(DuneSymlinkOrCopy)
 
@@ -546,6 +547,9 @@ macro(dune_project)
     message(FATAL_ERROR "You need to specify an absolute path to your compiler instead of just the compiler name. cmake >= 3.0 fixes this issue.")
   endif()
 
+  # check if CXX flag overloading has been enabled (see OverloadCompilerFlags.cmake)
+  initialize_compiler_script()
+
   # extract information from dune.module
   dune_module_information(${CMAKE_SOURCE_DIR})
   set(ProjectName            "${DUNE_MOD_NAME}")
@@ -677,13 +681,6 @@ macro(dune_project)
   include(Headercheck)
   setup_headercheck()
 
-  # check whether the user wants to append compile flags upon calling make
-  if(ALLOW_EXTRA_CXXFLAGS AND (${CMAKE_GENERATOR} MATCHES ".*Unix Makefiles.*"))
-    file(WRITE ${CMAKE_BINARY_DIR}/compiler.sh
-         "#!/bin/bash\nif [ -n \"$VERBOSE\" ] ; then\necho 1>&2 \"Additional flags: \$EXTRA_CXXFLAGS\"\nfi\nexec ${CMAKE_CXX_COMPILER} \"\$@\" \$EXTRA_CXXFLAGS")
-    exec_program(chmod ARGS "+x ${CMAKE_BINARY_DIR}/compiler.sh")
-    set(CMAKE_CXX_COMPILER ${CMAKE_BINARY_DIR}/compiler.sh)
-  endif()
 endmacro(dune_project)
 
 # create a new config.h file and overwrite the existing one
@@ -886,6 +883,10 @@ endif()
   include(CPack)
 
   feature_summary(WHAT ALL)
+
+  # check if CXX flag overloading has been enabled
+  # and write compiler script (see OverloadCompilerFlags.cmake)
+  finalize_compiler_script()
 endmacro(finalize_dune_project)
 
 macro(target_link_dune_default_libraries _target)

cmake/modules/OverloadCompilerFlags.cmake

+# check whether the user wants to overload compile flags upon calling make
+#
+# Provides the following macros:
+#
+#   initialize_compiler_script() : needs to be called before further flags are added to CMAKE_CXX_FLAGS
+#   finalize_compiler_script()   : needs to be called at the end of the cmake macros, e.g. in finalize_dune_project
+#
+#   By default this feature is disabled. Use -DALLOW_CXXFLAGS_OVERWRITE=ON to activate.
+#   Then the following is possible:
+#
+#   make CXXFLAGS="your flags" GRIDTYPE="grid type"
+#
+#   Furthermore any CPP variable of the form -DVAR=VALUE can be overloaded on the command line.
+#
+#   Note: If you don't know what this is or what it's good for, don't use it.
+#
+option(ALLOW_CXXFLAGS_OVERWRITE OFF)
+
+# check whether the user wants to append compile flags upon calling make
+if(ALLOW_EXTRA_CXXFLAGS AND (${CMAKE_GENERATOR} MATCHES ".*Unix Makefiles.*"))
+  message("ALLOW_EXTRA_CXXFLAGS is deprecated, please use -DALLOW_CXXFLAGS_OVERWRITE=ON")
+  set(ALLOW_CXXFLAGS_OVERWRITE ON)
+endif()
+
+# init compiler script and store CXX flags
+macro(initialize_compiler_script)
+  if(ALLOW_CXXFLAGS_OVERWRITE AND (${CMAKE_GENERATOR} MATCHES ".*Unix Makefiles.*"))
+    find_program (BASH_PROGRAM bash)
+    # set CXXFLAGS as environment variable
+    set( DEFAULT_CXXFLAGS ${CMAKE_CXX_FLAGS})
+    set( CMAKE_CXX_FLAGS "" )
+    set( DEFAULT_CXX_COMPILER ${CMAKE_CXX_COMPILER} )
+    set( COMPILER_SCRIPT_FILE "#!${BASH_PROGRAM}\nexec ${CMAKE_CXX_COMPILER} \"\$@\"")
+    file(WRITE ${CMAKE_BINARY_DIR}/compiler.sh "${COMPILER_SCRIPT_FILE}" )
+    exec_program(chmod ARGS "+x ${CMAKE_BINARY_DIR}/compiler.sh")
+    set(CMAKE_CXX_COMPILER ${CMAKE_BINARY_DIR}/compiler.sh)
+  endif()
+endmacro()
+
+# finalize compiler script and write it
+macro(finalize_compiler_script)
+  if(ALLOW_CXXFLAGS_OVERWRITE AND (${CMAKE_GENERATOR} MATCHES ".*Unix Makefiles.*"))
+    find_program (GREP_PROGRAM grep)
+    find_program (SED_PROGRAM  sed)
+    find_program (CUT_PROGRAM  cut)
+    find_program (ENV_PROGRAM  env)
+    find_program (ECHO_PROGRAM echo)
+    set( COMPILER_SCRIPT_FILE "#!${BASH_PROGRAM}\nSED=${SED_PROGRAM}\nGREP=${GREP_PROGRAM}")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nCUT=${CUT_PROGRAM}\nENV=${ENV_PROGRAM}\nECHO=${ECHO_PROGRAM}")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n# store flags\nFLAGS=\"\$@\"")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nMAKE_EXECUTABLE_NEW=0\n")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nif [ \"\$CXXFLAGS\" == \"\" ]; then\n  # default CXX flags\n  CXXFLAGS=\"${DEFAULT_CXXFLAGS}\"\nfi\n")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nGRIDS=\nCONFIG_H=${CMAKE_BINARY_DIR}/config.h")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nif [ \"\$GRIDTYPE\" != \"\" ]; then")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n  GRIDS=`\$GREP \"defined USED_[A-Z_]*_GRIDTYPE\" \$CONFIG_H | \$SED 's/\\(.*defined USED\\_\\)\\(.*\\)\\(\\_GRIDTYPE*\\)/\\2/g'`\nfi\n")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nOLDFLAGS=\$FLAGS\nFLAGS=")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nfor FLAG in \$OLDFLAGS; do")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n  NEWFLAG=\$FLAG\n  VARNAME=`\$ECHO \$FLAG | \$GREP \"\\-D\" | \$SED 's/-D//g'`")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n  for GRID in \$GRIDS; do\n    if [ \"\$VARNAME\" == \"\$GRID\" ]; then\n      NEWFLAG=\"-D\$GRIDTYPE\"\n      break\n    fi\n  done")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n  VARNAME=`\$ECHO \$VARNAME | \$GREP \"=\" | \$CUT -d \"=\" -f 1`")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n  if [ \"\$VARNAME\" != \"\" ]; then\n    VAR=`\$ENV | \$GREP \$VARNAME`\n    if [ \"\$VAR\" != \"\" ]; then")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n      # add variable from environment to flags list\n      NEWFLAG=\"-D\$VARNAME=\${!VARNAME}\"\n    fi\n  fi")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n  FLAGS=\"\$FLAGS \$NEWFLAG\"\ndone")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\n\$ECHO \"${DEFAULT_CXX_COMPILER} \$CXXFLAGS \$FLAGS\"")
+    set( COMPILER_SCRIPT_FILE "${COMPILER_SCRIPT_FILE}\nexec ${DEFAULT_CXX_COMPILER} \$CXXFLAGS \$FLAGS")
+    file(WRITE ${CMAKE_BINARY_DIR}/compiler.sh "${COMPILER_SCRIPT_FILE}" )
+    exec_program(chmod ARGS "+x ${CMAKE_BINARY_DIR}/compiler.sh")
+  endif()
+endmacro()