From 63bbb3768d3cf87459b6b66effa8726f38cc745a Mon Sep 17 00:00:00 2001 From: Ben Boeckel Date: Mon, 1 Jan 2024 11:04:29 -0500 Subject: cmLocalGenerator: ignore scanned sources for unity builds --- Help/manual/cmake-cxxmodules.7.rst | 4 ++++ Help/prop_sf/SKIP_UNITY_BUILD_INCLUSION.rst | 4 ++++ Help/prop_tgt/UNITY_BUILD.rst | 5 +++++ Source/cmLocalGenerator.cxx | 9 +++++++++ 4 files changed, 22 insertions(+) diff --git a/Help/manual/cmake-cxxmodules.7.rst b/Help/manual/cmake-cxxmodules.7.rst index b4c9cf1..3ee6645 100644 --- a/Help/manual/cmake-cxxmodules.7.rst +++ b/Help/manual/cmake-cxxmodules.7.rst @@ -30,6 +30,10 @@ following queries. The first query that provides a yes/no answer is used. - Otherwise, the source file will be scanned if the compiler and generator support scanning. See policy :policy:`CMP0155`. +Note that any scanned source will be excluded from any unity build (see +:prop_tgt:`UNITY_BUILD`) because module-related statements can only happen at +one place within a C++ translation unit. + Compiler Support ================ diff --git a/Help/prop_sf/SKIP_UNITY_BUILD_INCLUSION.rst b/Help/prop_sf/SKIP_UNITY_BUILD_INCLUSION.rst index ae526ac..38a0a78 100644 --- a/Help/prop_sf/SKIP_UNITY_BUILD_INCLUSION.rst +++ b/Help/prop_sf/SKIP_UNITY_BUILD_INCLUSION.rst @@ -11,3 +11,7 @@ in the same way as it would with unity builds disabled. This property helps with "ODR (One definition rule)" problems where combining a particular source file with others might lead to build errors or other unintended side effects. + +Note that sources which are scanned for C++ modules (see +:manual:`cmake-cxxmodules(7)`) are not eligible for unity build inclusion and +will automatically be excluded. diff --git a/Help/prop_tgt/UNITY_BUILD.rst b/Help/prop_tgt/UNITY_BUILD.rst index f827a20..9d68250 100644 --- a/Help/prop_tgt/UNITY_BUILD.rst +++ b/Help/prop_tgt/UNITY_BUILD.rst @@ -64,6 +64,11 @@ a number of measures to help address such problems: :prop_sf:`INCLUDE_DIRECTORIES` source property will not be combined into a unity source. +* Any source file which is scanned for C++ module sources via + :prop_tgt:`CXX_SCAN_FOR_MODULES`, :prop_sf:`CXX_SCAN_FOR_MODULES`, or + membership of a ``CXX_MODULES`` file set will not be combined into a unity + source. See :manual:`cmake-cxxmodules(7)` for details. + * Projects can prevent an individual source file from being combined into a unity source by setting its :prop_sf:`SKIP_UNITY_BUILD_INCLUSION` source property to true. This can be a more effective way to prevent diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx index 168cd41..7337ea2 100644 --- a/Source/cmLocalGenerator.cxx +++ b/Source/cmLocalGenerator.cxx @@ -3134,6 +3134,15 @@ void cmLocalGenerator::AddUnityBuild(cmGeneratorTarget* target) std::vector sources; target->GetSourceFiles(sources, configs[ci]); for (cmSourceFile* sf : sources) { + // Files which need C++ scanning cannot participate in unity builds as + // there is a single place in TUs that may perform module-dependency bits + // and a unity source cannot `#include` them in-order and represent a + // valid TU. + if (sf->GetLanguage() == "CXX"_s && + target->NeedDyndepForSource("CXX", configs[ci], sf)) { + continue; + } + auto mi = index.find(sf); if (mi == index.end()) { unitySources.emplace_back(sf); -- cgit v0.12