Merge topic 'clang-scan-deps-failed-scan'

77a7edb73f Clang-CXX: copy into the dyndep output on success

Acked-by: Kitware Robot <[email protected]>
Acked-by: Namniav W <[email protected]>
Merge-request: !8991

Modules/Compiler/Clang-CXX.cmake

@@ -32,6 +32,13 @@ endif()
 
 if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0)
   if("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
+    if (CMAKE_HOST_WIN32)
+      # `rename` doesn't overwrite and doesn't retry in case of "target file is
+      # busy".
+      set(_clang_scan_deps_mv "\"${CMAKE_COMMAND}\" -E rename")
+    else ()
+      set(_clang_scan_deps_mv "mv")
+    endif ()
     string(CONCAT CMAKE_CXX_SCANDEP_SOURCE
       "\"${CMAKE_CXX_COMPILER_CLANG_SCAN_DEPS}\""
       " -format=p1689"
@@ -40,7 +47,15 @@ if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0)
       " -x c++ <SOURCE> -c -o <OBJECT>"
       " -MT <DYNDEP_FILE>"
       " -MD -MF <DEP_FILE>"
-      " > <DYNDEP_FILE>")
+      # Write to a temporary file. If the scan fails, we do not want to update
+      # the actual output file as `ninja` (at least) assumes that failed
+      # commands either delete or leave output files alone. See Issue#25419.
+      " > <DYNDEP_FILE>.tmp"
+      # We cannot use `copy_if_different` as the rule does not have a feature
+      # analogous to `ninja`'s `restat = 1`. It would also leave behind the
+      # `.tmp` file.
+      " && ${_clang_scan_deps_mv} <DYNDEP_FILE>.tmp <DYNDEP_FILE>")
+    unset(_clang_scan_deps_mv)
     set(CMAKE_CXX_MODULE_MAP_FORMAT "clang")
     set(CMAKE_CXX_MODULE_MAP_FLAG "@<MODULE_MAP_FILE>")
     set(CMAKE_CXX_MODULE_BMI_ONLY_FLAG "--precompile")

Tests/RunCMake/CXXModules/examples/scan_properties/CMakeLists.txt

@@ -13,8 +13,8 @@ endif ()
 # if not.
 string(APPEND CMAKE_CXX_MODULE_MAP_FLAG
   " -DCMAKE_SCANNED_THIS_SOURCE")
-string(APPEND CMAKE_CXX_SCANDEP_SOURCE
-  " -DCMAKE_SCANNED_THIS_SOURCE")
+string(REPLACE "<DEFINES>" "<DEFINES> -DCMAKE_SCANNED_THIS_SOURCE"
+  CMAKE_CXX_SCANDEP_SOURCE "${CMAKE_CXX_SCANDEP_SOURCE}")
 
 set_property(SOURCE always_scan.cxx
   PROPERTY CXX_SCAN_FOR_MODULES 1)