VS: Consider macros with values when determining CharacterSet

In order to determine what character-set (Unicode, Multi-Byte, none)
shall be set in the generated `*.vcxproj` files, CMake checks if one of
the macros `_UNICODE` or `_SBCS` are defined.
However, as these macros can be defined with or without a value, the
check should always recognize these macros whether they are defined with
a value or without. That is now assured by this commit.

Fixes: #25379

Source/cmVisualStudioGeneratorOptions.cxx

@@ -137,14 +137,18 @@ bool cmVisualStudioGeneratorOptions::IsManaged() const
 bool cmVisualStudioGeneratorOptions::UsingUnicode() const
 {
   // Look for a _UNICODE definition.
-  return std::any_of(this->Defines.begin(), this->Defines.end(),
-                     [](std::string const& di) { return di == "_UNICODE"_s; });
+  return std::any_of(
+    this->Defines.begin(), this->Defines.end(), [](std::string const& di) {
+      return di == "_UNICODE"_s || cmHasLiteralPrefix(di, "_UNICODE=");
+    });
 }
 bool cmVisualStudioGeneratorOptions::UsingSBCS() const
 {
   // Look for a _SBCS definition.
-  return std::any_of(this->Defines.begin(), this->Defines.end(),
-                     [](std::string const& di) { return di == "_SBCS"_s; });
+  return std::any_of(
+    this->Defines.begin(), this->Defines.end(), [](std::string const& di) {
+      return di == "_SBCS"_s || cmHasLiteralPrefix(di, "_SBCS=");
+    });
 }
 
 void cmVisualStudioGeneratorOptions::FixCudaCodeGeneration()

Tests/RunCMake/VS10Project/RunCMakeTest.cmake

@@ -11,6 +11,9 @@ run_cmake(CustomCommandGenex)
 if(NOT RunCMake_GENERATOR MATCHES "^Visual Studio 1[1-5] ")
   run_cmake(CustomCommandParallel)
 endif()
+run_cmake_with_options(VsCharacterSet -DSET_CHARSET=MultiByte)
+run_cmake_with_options(VsCharacterSet -DSET_CHARSET=Unicode)
+run_cmake_with_options(VsCharacterSet -DSET_CHARSET=NotSet)
 run_cmake(VsCsharpSourceGroup)
 run_cmake(VsCSharpCompilerOpts)
 run_cmake(ExplicitCMakeLists)

Tests/RunCMake/VS10Project/VsCharacterSet-check.cmake

@@ -0,0 +1,49 @@
+macro(check_project_file projectFile outvar)
+  set(insideConfiguration FALSE)
+  set(characterSetFound FALSE)
+
+  if(NOT EXISTS "${projectFile}")
+    set(RunCMake_TEST_FAILED "Project file ${projectFile} does not exist.")
+    return()
+  endif()
+
+  string(REPLACE "${RunCMake_TEST_BINARY_DIR}/" "" projectName ${projectFile})
+
+  file(STRINGS "${projectFile}" lines)
+  foreach(line IN LISTS lines)
+    if(line MATCHES "^ *<PropertyGroup Condition=\"'[$][(]Configuration[)]|[$][(]Platform[)]'=='([^\"])+\" Label=\"Configuration\">.*$")
+      set(insideConfiguration TRUE)
+    elseif(insideConfiguration)
+      if(line MATCHES "^ *</PropertyGroup>.*$")
+        set(insideConfiguration FALSE)
+      elseif(line MATCHES "^ *<CharacterSet>(.+)</CharacterSet>*$")
+        message(STATUS "Found CharacterSet = ${CMAKE_MATCH_1} in PropertyGroup 'Configuration' in ${projectName}")
+        set(characterSetFound TRUE)
+        set(${outvar} ${CMAKE_MATCH_1})
+      endif()
+    endif()
+  endforeach()
+  if(NOT characterSetFound)
+    set(RunCMake_TEST_FAILED "CharacterSet not found in \"Configuration\" propertygroup in ${projectName}")
+    return() # This should intentionally return from the caller, not the macro
+  endif()
+endmacro()
+
+check_project_file("${RunCMake_TEST_BINARY_DIR}/CMakeFiles/${CMAKE_VERSION}/CompilerIdCXX/CompilerIdCXX.vcxproj" MULTI_BYTE_CHARSET)
+check_project_file("${RunCMake_TEST_BINARY_DIR}/foo.vcxproj" OVERRIDDEN_CHARSET)
+
+if (NOT "${MULTI_BYTE_CHARSET}" STREQUAL "MultiByte")
+  set(RunCMake_TEST_FAILED "Default character-set (\"MultiByte\") was overridden (it shouldn't)")
+  return()
+endif()
+
+if(NOT EXISTS "${RunCMake_TEST_BINARY_DIR}/set_charset.txt")
+  set(RunCMake_TEST_FAILED "File 'set_charset.txt' with set charset does not exist.")
+  return()
+endif()
+file(STRINGS "${RunCMake_TEST_BINARY_DIR}/set_charset.txt" SET_CHARSET)
+
+if (NOT "${OVERRIDDEN_CHARSET}" STREQUAL "${SET_CHARSET}")
+  set(RunCMake_TEST_FAILED "Failed to override the character-set with \"${SET_CHARSET}\"")
+  return()
+endif()

Tests/RunCMake/VS10Project/VsCharacterSet.cmake

@@ -0,0 +1,17 @@
+enable_language(CXX)
+
+# Write value of `SET_CHARSET` for comparison later.
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/set_charset.txt" "${SET_CHARSET}")
+
+# Set macro which determines the character-set.
+if("${SET_CHARSET}" STREQUAL "MultiByte")
+  add_compile_definitions(_MBCS=1)
+endif()
+if("${SET_CHARSET}" STREQUAL "NotSet")
+  add_compile_definitions(_SBCS=1)
+endif()
+if("${SET_CHARSET}" STREQUAL "Unicode")
+  add_compile_definitions(_UNICODE=1)
+endif()
+
+add_library(foo foo.cpp)