FASTBuild: allow disabling of caching / distribution

Compilation is complicated. Caching / distribution is even more
complicated. Sometimes there are bugs (in compilers as well as in
FASTBuild), so export the option to disable those features for CMake
targets.

Auxiliary/vim/syntax/cmake.vim

@@ -206,6 +206,8 @@ syn keyword cmakeProperty contained
             \ EXPORT_PROPERTIES
             \ EXTERNAL_OBJECT
             \ EchoString
+            \ FASTBUILD_CACHING
+            \ FASTBUILD_DISTRIBUTION
             \ FAIL_REGULAR_EXPRESSION
             \ FIND_LIBRARY_USE_LIB32_PATHS
             \ FIND_LIBRARY_USE_LIB64_PATHS

Help/generator/FASTBuild.rst

@@ -40,6 +40,17 @@ The following variables can be used to configure this generator:
 * :variable:`CMAKE_FASTBUILD_USE_LIGHTCACHE`
 * :variable:`CMAKE_FASTBUILD_VERBOSE_GENERATOR`
 
+Target Properties
+-----------------
+
+The following target properties can be used to fine-tune behavior on a
+per-target basis:
+
+* :prop_tgt:`FASTBUILD_CACHING` –
+  disables caching for a specific target.
+* :prop_tgt:`FASTBUILD_DISTRIBUTION` –
+  disables distributed compilation for a specific target.
+
 Notes
 -----
 

Help/manual/cmake-properties.7.rst

@@ -226,6 +226,8 @@ Properties on Targets
    /prop_tgt/EXPORT_NAME
    /prop_tgt/EXPORT_NO_SYSTEM
    /prop_tgt/EXPORT_PROPERTIES
+   /prop_tgt/FASTBUILD_CACHING
+   /prop_tgt/FASTBUILD_DISTRIBUTION
    /prop_tgt/FOLDER
    /prop_tgt/Fortran_BUILDING_INTRINSIC_MODULES
    /prop_tgt/Fortran_FORMAT

Help/prop_tgt/FASTBUILD_CACHING.rst

@@ -0,0 +1,19 @@
+FASTBUILD_CACHING
+-----------------
+
+.. versionadded:: 4.2
+
+A target property that controls whether caching is enabled for the given
+target in the generated ``fbuild.bff``.
+
+If set to ``OFF``, the :generator:`FASTBuild` generator disables caching
+features for this target. This is useful for targets that are known to be
+unreliably cached or not worth caching.
+
+Example:
+
+.. code-block:: cmake
+
+  set_property(TARGET my_target PROPERTY FASTBUILD_CACHING OFF)
+
+Defaults to ``ON``.

Help/prop_tgt/FASTBUILD_DISTRIBUTION.rst

@@ -0,0 +1,19 @@
+FASTBUILD_DISTRIBUTION
+----------------------
+
+.. versionadded:: 4.2
+
+A target property that controls whether distribution is enabled for the given
+target in the generated ``fbuild.bff``.
+
+If set to ``OFF``, the :generator:`FASTBuild` generator disables distributed
+compilation for this target. This can be helpful for targets that are fast to
+build locally or are incompatible with distributed execution.
+
+Example:
+
+.. code-block:: cmake
+
+  set_property(TARGET my_target PROPERTY FASTBUILD_DISTRIBUTION OFF)
+
+Defaults to ``ON``.

Source/cmFastbuildNormalTargetGenerator.cxx

@@ -1220,6 +1220,13 @@ cmFastbuildNormalTargetGenerator::GenerateObjects()
 
     std::string const staticCheckOptions = ComputeCodeCheckOptions(srcFile);
 
+    auto const isDisabled = [this](char const* prop) {
+      auto const propValue = this->GeneratorTarget->GetProperty(prop);
+      return propValue && propValue.IsOff();
+    };
+    bool const disableCaching = isDisabled("FASTBUILD_CACHING");
+    bool const disableDistribution = isDisabled("FASTBUILD_DISTRIBUTION");
+
     for (auto const& arch : this->GetArches()) {
       std::string const compileOptions = GetCompileOptions(srcFile, arch);
 
@@ -1261,6 +1268,12 @@ cmFastbuildNormalTargetGenerator::GenerateObjects()
       if (!objectListNode.CompilerOptions.empty()) {
         continue;
       }
+      if (disableCaching) {
+        objectListNode.AllowCaching = false;
+      }
+      if (disableDistribution) {
+        objectListNode.AllowDistribution = false;
+      }
 
       objectListNode.CompilerOutputPath = objOutDirWithPossibleSubdir;
       LogMessage(cmStrCat("Output path: ", objectListNode.CompilerOutputPath));

Source/cmGlobalFastbuildGenerator.cxx

@@ -1174,6 +1174,12 @@ void cmGlobalFastbuildGenerator::WriteObjectList(
                   Quote(ObjectList.CompilerOutputExtension), 2);
     WriteVariable("CompilerOutputKeepBaseExtension", "true", 2);
     WriteArray("CompilerInputFiles", Wrap(ObjectList.CompilerInputFiles), 2);
+    if (!ObjectList.AllowCaching) {
+      WriteVariable("AllowCaching", "false", 2);
+    }
+    if (!ObjectList.AllowDistribution) {
+      WriteVariable("AllowDistribution", "false", 2);
+    }
     if (ObjectList.Hidden) {
       WriteVariable("Hidden", "true", 2);
     }

Source/cmGlobalFastbuildGenerator.h

@@ -207,6 +207,8 @@ struct FastbuildObjectListNode : public FastbuildTargetBase
   std::string PCHOptions;
 
   std::vector<std::string> CompilerInputFiles;
+  bool AllowCaching = true;
+  bool AllowDistribution = true;
 
   std::set<std::string> ObjectOutputs;
   std::set<std::string> ObjectDepends;

Tests/RunCMake/CMakeLists.txt

@@ -213,6 +213,9 @@ elseif(CMake_TEST_Qt5)
     set(ninja_test_with_qt_version 5)
   endif()
 endif()
+if(CMAKE_GENERATOR MATCHES "FASTBuild")
+  add_RunCMake_test(FASTBuild)
+endif()
 if(CMAKE_GENERATOR MATCHES "Ninja")
   set(Ninja_ARGS
     -DCMAKE_C_COMPILER_ID=${CMAKE_C_COMPILER_ID}

Tests/RunCMake/FASTBuild/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 3.10)
+project(${RunCMake_TEST})
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/FASTBuild/DisableCaching-check.cmake

@@ -0,0 +1,2 @@
+set(REGEX_TO_MATCH "AllowCaching = false")
+include(${RunCMake_SOURCE_DIR}/check.cmake)

Tests/RunCMake/FASTBuild/DisableCaching.cmake

@@ -0,0 +1,2 @@
+add_executable(main main.cpp)
+set_property(TARGET main PROPERTY FASTBUILD_CACHING OFF)

Tests/RunCMake/FASTBuild/DisableDistribution-check.cmake

@@ -0,0 +1,2 @@
+set(REGEX_TO_MATCH "AllowDistribution = false")
+include(${RunCMake_SOURCE_DIR}/check.cmake)

Tests/RunCMake/FASTBuild/DisableDistribution.cmake

@@ -0,0 +1,2 @@
+add_executable(main main.cpp)
+set_target_properties(main PROPERTIES FASTBUILD_DISTRIBUTION OFF)

Tests/RunCMake/FASTBuild/RunCMakeTest.cmake

@@ -0,0 +1,4 @@
+include(RunCMake)
+
+run_cmake(DisableCaching)
+run_cmake(DisableDistribution)

Tests/RunCMake/FASTBuild/check.cmake

@@ -0,0 +1,11 @@
+set(fbuild_bff "${RunCMake_TEST_BINARY_DIR}/fbuild.bff")
+
+if(NOT EXISTS "${fbuild_bff}")
+  set(RunCMake_TEST_FAILED "Generator output file is missing:\n ${fbuild_bff}")
+  return()
+endif()
+file(READ "${fbuild_bff}" fbuild_bff)
+
+if(NOT fbuild_bff MATCHES ${REGEX_TO_MATCH})
+    set(RunCMake_TEST_FAILED "Regex '${REGEX_TO_MATCH}' not found in the generated file ${RunCMake_TEST_BINARY_DIR}/fbuild.bff")
+endif()

Tests/RunCMake/FASTBuild/main.cpp

@@ -0,0 +1,4 @@
+int main()
+{
+  return 0;
+}