Add options to launch the compiler through tools like ccache or distcc

Create a <LANG>_COMPILER_LAUNCHER target property (initialized by a
CMAKE_<LANG>_COMPILER_LAUNCHER variable) to specify a compiler launcher
tool.  This will supersede the CMAKE_<LANG>_COMPILER_ARG1 approach to
using such tools.  The old approach set CMAKE_<LANG>_COMPILER to the
launcher tool while the new approach leaves this variable set to the
actual compiler.

Implement this property for Makefile and Ninja generators.  It cannot be
implemented for VS or Xcode generators as the IDE build tools offer no
such hooks.

13 files changed, 49 insertions, 0 deletions

diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 592b5e4..2a4108f 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -232,4 +232,5 @@ endif()
 if("${CMAKE_GENERATOR}" MATCHES "Make|Ninja")
   add_executable(pseudo_iwyu pseudo_iwyu.c)
   add_RunCMake_test(IncludeWhatYouUse -DPSEUDO_IWYU=$<TARGET_FILE:pseudo_iwyu>)
+  add_RunCMake_test(CompilerLauncher)
 endif()
diff --git a/Tests/RunCMake/CompilerLauncher/C-Build-stdout.txt b/Tests/RunCMake/CompilerLauncher/C-Build-stdout.txt
new file mode 100644
index 0000000..3313e31
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/C-Build-stdout.txt
@@ -0,0 +1 @@
+.*-E env USED_LAUNCHER=1.*
diff --git a/Tests/RunCMake/CompilerLauncher/C-launch-Build-stdout.txt b/Tests/RunCMake/CompilerLauncher/C-launch-Build-stdout.txt
new file mode 100644
index 0000000..3313e31
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/C-launch-Build-stdout.txt
@@ -0,0 +1 @@
+.*-E env USED_LAUNCHER=1.*
diff --git a/Tests/RunCMake/CompilerLauncher/C-launch.cmake b/Tests/RunCMake/CompilerLauncher/C-launch.cmake
new file mode 100644
index 0000000..e66ca20
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/C-launch.cmake
@@ -0,0 +1,3 @@
+set(CTEST_USE_LAUNCHERS 1)
+include(CTestUseLaunchers)
+include(C.cmake)
diff --git a/Tests/RunCMake/CompilerLauncher/C.cmake b/Tests/RunCMake/CompilerLauncher/C.cmake
new file mode 100644
index 0000000..67bf7c4
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/C.cmake
@@ -0,0 +1,4 @@
+enable_language(C)
+set(CMAKE_C_COMPILER_LAUNCHER "${CMAKE_COMMAND};-E;env;USED_LAUNCHER=1")
+set(CMAKE_VERBOSE_MAKEFILE TRUE)
+add_executable(main main.c)
diff --git a/Tests/RunCMake/CompilerLauncher/CMakeLists.txt b/Tests/RunCMake/CompilerLauncher/CMakeLists.txt
new file mode 100644
index 0000000..18dfd26
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/CMakeLists.txt
@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 3.2)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)
diff --git a/Tests/RunCMake/CompilerLauncher/CXX-Build-stdout.txt b/Tests/RunCMake/CompilerLauncher/CXX-Build-stdout.txt
new file mode 100644
index 0000000..3313e31
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/CXX-Build-stdout.txt
@@ -0,0 +1 @@
+.*-E env USED_LAUNCHER=1.*
diff --git a/Tests/RunCMake/CompilerLauncher/CXX-launch-Build-stdout.txt b/Tests/RunCMake/CompilerLauncher/CXX-launch-Build-stdout.txt
new file mode 100644
index 0000000..3313e31
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/CXX-launch-Build-stdout.txt
@@ -0,0 +1 @@
+.*-E env USED_LAUNCHER=1.*
diff --git a/Tests/RunCMake/CompilerLauncher/CXX-launch.cmake b/Tests/RunCMake/CompilerLauncher/CXX-launch.cmake
new file mode 100644
index 0000000..3002c9d
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/CXX-launch.cmake
@@ -0,0 +1,3 @@
+set(CTEST_USE_LAUNCHERS 1)
+include(CTestUseLaunchers)
+include(CXX.cmake)
diff --git a/Tests/RunCMake/CompilerLauncher/CXX.cmake b/Tests/RunCMake/CompilerLauncher/CXX.cmake
new file mode 100644
index 0000000..cdd3478
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/CXX.cmake
@@ -0,0 +1,4 @@
+enable_language(CXX)
+set(CMAKE_CXX_COMPILER_LAUNCHER "${CMAKE_COMMAND};-E;env;USED_LAUNCHER=1")
+set(CMAKE_VERBOSE_MAKEFILE TRUE)
+add_executable(main main.cxx)
diff --git a/Tests/RunCMake/CompilerLauncher/RunCMakeTest.cmake b/Tests/RunCMake/CompilerLauncher/RunCMakeTest.cmake
new file mode 100644
index 0000000..5884d5c
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/RunCMakeTest.cmake
@@ -0,0 +1,23 @@
+include(RunCMake)
+
+function(run_compiler_launcher lang)
+  # Use a single build tree for tests without cleaning.
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/${lang}-build)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+  run_cmake(${lang})
+
+  set(RunCMake_TEST_OUTPUT_MERGE 1)
+  if("${RunCMake_GENERATOR}" STREQUAL "Ninja")
+    set(verbose_args -- -v)
+  endif()
+  run_cmake_command(${lang}-Build ${CMAKE_COMMAND} --build . ${verbose_args})
+endfunction()
+
+run_compiler_launcher(C)
+run_compiler_launcher(CXX)
+if (NOT RunCMake_GENERATOR STREQUAL "Watcom WMake")
+  run_compiler_launcher(C-launch)
+  run_compiler_launcher(CXX-launch)
+endif()
diff --git a/Tests/RunCMake/CompilerLauncher/main.c b/Tests/RunCMake/CompilerLauncher/main.c
new file mode 100644
index 0000000..03b2213
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/main.c
@@ -0,0 +1,3 @@
+int main(void) {
+  return 0;
+}
diff --git a/Tests/RunCMake/CompilerLauncher/main.cxx b/Tests/RunCMake/CompilerLauncher/main.cxx
new file mode 100644
index 0000000..76e8197
--- /dev/null
+++ b/Tests/RunCMake/CompilerLauncher/main.cxx
@@ -0,0 +1 @@
+int main() { return 0; }