execute_process: Change default ENCODING to UTF-8

Windows is heading toward making UTF-8 the preferred MBCS.  As CMake's
internal encoding, `UTF-8` is effectively equivalent to `NONE`, which
was CMake's behavior prior to 3.15's accidental change to `AUTO`.
Behavior of `ENCODING UTF-8` is independent of CMake's internal
encoding, making it in principle a better default than `NONE`.

Add policy CMP0176 for compatibility and to document the default's
history.

Fixes: #26262

8 files changed, 21 insertions, 2 deletions

diff --git a/Tests/RunCMake/execute_process/Encoding-common.cmake b/Tests/RunCMake/execute_process/Encoding-common.cmake
index e13be75..fda1c2d 100644
--- a/Tests/RunCMake/execute_process/Encoding-common.cmake
+++ b/Tests/RunCMake/execute_process/Encoding-common.cmake
@@ -2,7 +2,12 @@ if(ENCODING)
   set(maybe_ENCODING ENCODING ${ENCODING})
 else()
   set(maybe_ENCODING "")
-  set(ENCODING AUTO) # execute_process's default ENCODING
+  cmake_policy(GET CMP0176 cmp0176)
+  if(cmp0176 STREQUAL "NEW")
+    set(ENCODING UTF-8) # execute_process's default ENCODING
+  else()
+    set(ENCODING AUTO) # execute_process's default ENCODING
+  endif()
 endif()
 execute_process(
   COMMAND ${TEST_ENCODING_EXE} ${ENCODING} ${CMAKE_CURRENT_LIST_DIR}/Encoding${ENCODING}-stderr.txt
diff --git a/Tests/RunCMake/execute_process/Encoding-windows.cmake b/Tests/RunCMake/execute_process/Encoding-windows.cmake
index 69b9bc7..d51589c 100644
--- a/Tests/RunCMake/execute_process/Encoding-windows.cmake
+++ b/Tests/RunCMake/execute_process/Encoding-windows.cmake
@@ -1,3 +1,7 @@
+if(CMP0176 STREQUAL "NEW")
+  cmake_policy(SET CMP0176 NEW)
+endif()
+
 # Set the console code page.
 execute_process(COMMAND cmd /c chcp ${CODEPAGE})
 
diff --git a/Tests/RunCMake/execute_process/Encoding.cmake b/Tests/RunCMake/execute_process/Encoding.cmake
index 206a71b..61d2c22 100644
--- a/Tests/RunCMake/execute_process/Encoding.cmake
+++ b/Tests/RunCMake/execute_process/Encoding.cmake
@@ -1,9 +1,12 @@
 if(CMAKE_HOST_WIN32 AND CODEPAGE)
+  cmake_policy(GET CMP0176 CMP0176)
+
   # Run cmake in a new Window to isolate its console code page.
   execute_process(COMMAND cmd /c start /min /wait ""
     ${CMAKE_COMMAND} -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE}
                      -DENCODING=${ENCODING}
                      -DCODEPAGE=${CODEPAGE}
+                     -DCMP0176=${CMP0176}
                      -P ${CMAKE_CURRENT_LIST_DIR}/Encoding-windows.cmake)
 
   # Load our internal UTF-8 representation of the output.
diff --git a/Tests/RunCMake/execute_process/EncodingCMP0176-NEW-stderr.txt b/Tests/RunCMake/execute_process/EncodingCMP0176-NEW-stderr.txt
new file mode 100644
index 0000000..9fd0dcd
--- /dev/null
+++ b/Tests/RunCMake/execute_process/EncodingCMP0176-NEW-stderr.txt
@@ -0,0 +1,2 @@
+Chinese Hindi  Greek English Russian
+注意    यूनिकोड είναι very    здорово!
diff --git a/Tests/RunCMake/execute_process/EncodingCMP0176-NEW.cmake b/Tests/RunCMake/execute_process/EncodingCMP0176-NEW.cmake
new file mode 100644
index 0000000..b23ff59
--- /dev/null
+++ b/Tests/RunCMake/execute_process/EncodingCMP0176-NEW.cmake
@@ -0,0 +1,3 @@
+cmake_policy(SET CMP0176 NEW)
+# No explicit ENCODING option; fall back to default.
+include(${CMAKE_CURRENT_LIST_DIR}/Encoding.cmake)
diff --git a/Tests/RunCMake/execute_process/EncodingDefault-stderr.txt b/Tests/RunCMake/execute_process/EncodingCMP0176-OLD-stderr.txt
index b4cf27a..b4cf27a 100644
--- a/Tests/RunCMake/execute_process/EncodingDefault-stderr.txt
+++ b/Tests/RunCMake/execute_process/EncodingCMP0176-OLD-stderr.txt
diff --git a/Tests/RunCMake/execute_process/EncodingDefault.cmake b/Tests/RunCMake/execute_process/EncodingCMP0176-OLD.cmake
index 60b1eb6..8057176 100644
--- a/Tests/RunCMake/execute_process/EncodingDefault.cmake
+++ b/Tests/RunCMake/execute_process/EncodingCMP0176-OLD.cmake
@@ -1,3 +1,4 @@
+cmake_policy(SET CMP0176 OLD)
 # No explicit ENCODING option; fall back to default.
 set(CODEPAGE 54936)
 include(${CMAKE_CURRENT_LIST_DIR}/Encoding.cmake)
diff --git a/Tests/RunCMake/execute_process/RunCMakeTest.cmake b/Tests/RunCMake/execute_process/RunCMakeTest.cmake
index b3ebdca..2516de0 100644
--- a/Tests/RunCMake/execute_process/RunCMakeTest.cmake
+++ b/Tests/RunCMake/execute_process/RunCMakeTest.cmake
@@ -9,7 +9,8 @@ run_cmake_command(MergeOutputVars ${CMAKE_COMMAND} -P ${RunCMake_SOURCE_DIR}/Mer
 
 run_cmake(EncodingMissing)
 if(TEST_ENCODING_EXE)
-  run_cmake_script(EncodingDefault -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE})
+  run_cmake_script(EncodingCMP0176-NEW -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE})
+  run_cmake_script(EncodingCMP0176-OLD -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE})
   run_cmake_script(EncodingAUTO -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE})
   run_cmake_script(EncodingUTF-8 -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE})
   run_cmake_script(EncodingUTF8 -DTEST_ENCODING_EXE=${TEST_ENCODING_EXE})