From 211a9deac1d4144c7d7ce18ecb6c5d21c4854eaa Mon Sep 17 00:00:00 2001
From: "Klein, Thorsten (BSH)" <thorsten.klein@bshg.com>
Date: Mon, 28 Mar 2022 13:01:08 +0200
Subject: Preserve CMAKE_${lang}_COMPILER_ARG1 from existing CMakeCache.txt

`CMAKE_<LANG>_COMPILER` may be a list if it was defined by a toolchain
file.  In this case we move the args to `CMAKE_<LANG>_COMPILER_ARG1`.
If `CMAKE_<LANG>_COMPILER` is not a list, then it might have been cached
by a previous run that split the `CC` or `CXX` environment variable into
`CMAKE_<LANG>_COMPILER` and `CMAKE_<LANG>_COMPILER_ARG1`.  In this
latter case, avoid clobbering `CMAKE_<LANG>_COMPILER_ARG1`.

Fixes: #23358
---
 Modules/CMakeDetermineCompiler.cmake           | 12 +++++++++---
 Tests/RunCMake/CompilerArgs/C-stdout.txt       |  1 +
 Tests/RunCMake/CompilerArgs/C.cmake            |  1 +
 Tests/RunCMake/CompilerArgs/CXX-stdout.txt     |  1 +
 Tests/RunCMake/CompilerArgs/CXX.cmake          |  1 +
 Tests/RunCMake/CompilerArgs/RunCMakeTest.cmake | 10 ++++++++++
 6 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100644 Tests/RunCMake/CompilerArgs/C-stdout.txt
 create mode 100644 Tests/RunCMake/CompilerArgs/CXX-stdout.txt

diff --git a/Modules/CMakeDetermineCompiler.cmake b/Modules/CMakeDetermineCompiler.cmake
index aec86d9..ec2a865 100644
--- a/Modules/CMakeDetermineCompiler.cmake
+++ b/Modules/CMakeDetermineCompiler.cmake
@@ -119,9 +119,15 @@ macro(_cmake_find_compiler_path lang)
     # (e.g. via ctest) or set in CMAKE_TOOLCHAIN_FILE
     # if CMAKE_${lang}_COMPILER is a list, use the first item as
     # CMAKE_${lang}_COMPILER and the rest as CMAKE_${lang}_COMPILER_ARG1
-    set(CMAKE_${lang}_COMPILER_ARG1 "${CMAKE_${lang}_COMPILER}")
-    list(POP_FRONT CMAKE_${lang}_COMPILER_ARG1 CMAKE_${lang}_COMPILER)
-    list(JOIN CMAKE_${lang}_COMPILER_ARG1 " " CMAKE_${lang}_COMPILER_ARG1)
+    # Otherwise, preserve any existing CMAKE_${lang}_COMPILER_ARG1 that might
+    # have been saved by CMakeDetermine${lang}Compiler in a previous run.
+    list(LENGTH CMAKE_${lang}_COMPILER _CMAKE_${lang}_COMPILER_LENGTH)
+    if(_CMAKE_${lang}_COMPILER_LENGTH GREATER 1)
+      set(CMAKE_${lang}_COMPILER_ARG1 "${CMAKE_${lang}_COMPILER}")
+      list(POP_FRONT CMAKE_${lang}_COMPILER_ARG1 CMAKE_${lang}_COMPILER)
+      list(JOIN CMAKE_${lang}_COMPILER_ARG1 " " CMAKE_${lang}_COMPILER_ARG1)
+    endif()
+    unset(_CMAKE_${lang}_COMPILER_LENGTH)
 
     # find the compiler in the PATH if necessary
     # if compiler (and arguments) comes from cache then synchronize cache with updated CMAKE_<LANG>_COMPILER
diff --git a/Tests/RunCMake/CompilerArgs/C-stdout.txt b/Tests/RunCMake/CompilerArgs/C-stdout.txt
new file mode 100644
index 0000000..e553cbb
--- /dev/null
+++ b/Tests/RunCMake/CompilerArgs/C-stdout.txt
@@ -0,0 +1 @@
+-- CMAKE_C_COMPILER_ARG1=' ?-DFOO1 -DFOO2'
diff --git a/Tests/RunCMake/CompilerArgs/C.cmake b/Tests/RunCMake/CompilerArgs/C.cmake
index 96b004b..0fbfdd2 100644
--- a/Tests/RunCMake/CompilerArgs/C.cmake
+++ b/Tests/RunCMake/CompilerArgs/C.cmake
@@ -1,3 +1,4 @@
 enable_language(C)
 set(CMAKE_VERBOSE_MAKEFILE TRUE)
+message(STATUS "CMAKE_C_COMPILER_ARG1='${CMAKE_C_COMPILER_ARG1}'")
 add_executable(main main.c)
diff --git a/Tests/RunCMake/CompilerArgs/CXX-stdout.txt b/Tests/RunCMake/CompilerArgs/CXX-stdout.txt
new file mode 100644
index 0000000..c543d3b
--- /dev/null
+++ b/Tests/RunCMake/CompilerArgs/CXX-stdout.txt
@@ -0,0 +1 @@
+-- CMAKE_CXX_COMPILER_ARG1=' ?-DFOO1 -DFOO2'
diff --git a/Tests/RunCMake/CompilerArgs/CXX.cmake b/Tests/RunCMake/CompilerArgs/CXX.cmake
index 3d2ee00..b6cf87e 100644
--- a/Tests/RunCMake/CompilerArgs/CXX.cmake
+++ b/Tests/RunCMake/CompilerArgs/CXX.cmake
@@ -1,3 +1,4 @@
 enable_language(CXX)
 set(CMAKE_VERBOSE_MAKEFILE TRUE)
+message(STATUS "CMAKE_CXX_COMPILER_ARG1='${CMAKE_CXX_COMPILER_ARG1}'")
 add_executable(main main.cxx)
diff --git a/Tests/RunCMake/CompilerArgs/RunCMakeTest.cmake b/Tests/RunCMake/CompilerArgs/RunCMakeTest.cmake
index 5e8b39b..62294cd 100644
--- a/Tests/RunCMake/CompilerArgs/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CompilerArgs/RunCMakeTest.cmake
@@ -31,6 +31,11 @@ function(run_compiler_env lang)
   run_cmake(${lang})
   set(RunCMake_TEST_NO_CLEAN 1)
   run_cmake_command(${lang}-Build ${CMAKE_COMMAND} --build . ${verbose_args})
+
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}/CMakeFiles")
+  set(RunCMake_TEST_VARIANT_DESCRIPTION "-env-cached")
+  run_cmake(${lang})
+  run_cmake_command(${lang}-Build ${CMAKE_COMMAND} --build . ${verbose_args})
 endfunction()
 
 function(run_compiler_tc lang)
@@ -42,6 +47,11 @@ function(run_compiler_tc lang)
   run_cmake(${lang})
   set(RunCMake_TEST_NO_CLEAN 1)
   run_cmake_command(${lang}-Build ${CMAKE_COMMAND} --build . ${verbose_args})
+
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}/CMakeFiles")
+  set(RunCMake_TEST_VARIANT_DESCRIPTION "-tc-cached")
+  run_cmake(${lang})
+  run_cmake_command(${lang}-Build ${CMAKE_COMMAND} --build . ${verbose_args})
 endfunction()
 
 set(langs C CXX)
-- 
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