CMP0210: Warn at most once per CMAKE_<LANG>_LINK_FLAGS variable

Additionally, add more testing for the warning case.

Issue: #21934

Source/cmGlobalGenerator.cxx

@@ -1386,6 +1386,11 @@ void cmGlobalGenerator::AddCMP0068WarnTarget(std::string const& target)
   this->CMP0068WarnTargets.insert(target);
 }
 
+bool cmGlobalGenerator::ShouldWarnCMP0210(std::string const& lang)
+{
+  return this->WarnedCMP0210Languages.insert(lang).second;
+}
+
 bool cmGlobalGenerator::CheckALLOW_DUPLICATE_CUSTOM_TARGETS() const
 {
   // If the property is not enabled then okay.
@@ -2101,6 +2106,7 @@ void cmGlobalGenerator::ClearGeneratorMembers()
   this->RuntimeDependencySets.clear();
   this->RuntimeDependencySetsByName.clear();
   this->WarnedExperimental.clear();
+  this->WarnedCMP0210Languages.clear();
 }
 
 bool cmGlobalGenerator::SupportsShortObjectNames() const

Source/cmGlobalGenerator.h

@@ -715,6 +715,8 @@ public:
     return configs;
   }
 
+  bool ShouldWarnCMP0210(std::string const& lang);
+
   bool ShouldWarnExperimental(cm::string_view featureName,
                               cm::string_view featureUuid);
 
@@ -967,6 +969,8 @@ private:
   // track targets to issue CMP0068 warning for.
   std::set<std::string> CMP0068WarnTargets;
 
+  std::unordered_set<std::string> WarnedCMP0210Languages;
+
   std::unordered_set<std::string> WarnedExperimental;
 
   mutable std::map<cmSourceFile*, std::set<cmGeneratorTarget const*>>

Source/cmLocalGenerator.cxx

@@ -3384,17 +3384,20 @@ void cmLocalGenerator::AddPerLanguageLinkFlags(std::string& flags,
       // their wishes), while also exempting cases when the latter variable
       // (substituted for the former spelling under the NEW behavior) is being
       // used legitimately by CMake.
+      // Additionally, WARN at most once per language, instead of on every
+      // target.
       if (!langLinkFlags.empty() &&
           target->GetType() != cmStateEnums::EXECUTABLE &&
           langLinkFlags !=
             this->Makefile->GetSafeDefinition(
-              cmStrCat("CMAKE_EXECUTABLE_CREATE_", lang, "_FLAGS"))) {
+              cmStrCat("CMAKE_EXECUTABLE_CREATE_", lang, "_FLAGS")) &&
+          this->GlobalGenerator->ShouldWarnCMP0210(lang)) {
         this->IssueMessage(
           MessageType::AUTHOR_WARNING,
           cmStrCat(cmPolicies::GetPolicyWarning(cmPolicies::CMP0210), "\n",
                    "For compatibility with older versions of CMake, ",
-                   "CMAKE_", lang, "_LINK_FLAGS will be ignored for target '",
-                   target->GetName(), "'."));
+                   "CMAKE_", lang, "_LINK_FLAGS will be ignored for all ",
+                   "non-EXECUTABLE targets which use these flags."));
       }
       CM_FALLTHROUGH;
     case cmPolicies::OLD:

Tests/RunCMake/LinkFlags/CMAKE_LANG_LINK_FLAGS-CMP0210-WARN-exe-stdout.txt

@@ -1 +0,0 @@
-.*BADFLAG.*

Tests/RunCMake/LinkFlags/CMAKE_LANG_LINK_FLAGS-CMP0210-WARN-exe_C-stdout.txt

@@ -0,0 +1 @@
+.*BADFLAG_C.*

Tests/RunCMake/LinkFlags/CMAKE_LANG_LINK_FLAGS-CMP0210-WARN-exe_CXX-result.txt

@@ -0,0 +1 @@
+[^0]

Tests/RunCMake/LinkFlags/CMAKE_LANG_LINK_FLAGS-CMP0210-WARN-exe_CXX-stdout.txt

@@ -0,0 +1 @@
+.*BADFLAG_CXX.*

Tests/RunCMake/LinkFlags/CMAKE_LANG_LINK_FLAGS-CMP0210-WARN-stdout.txt

@@ -4,5 +4,14 @@ CMake Warning \(dev\) in CMakeLists\.txt:
   the cmake_policy command to set the policy and suppress this warning\.
 
   For compatibility with older versions of CMake, CMAKE_C_LINK_FLAGS will be
-  ignored for target 'LinkFlags_shared'\.
+  ignored for all non-EXECUTABLE targets which use these flags.
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
+
+CMake Warning \(dev\) in CMakeLists\.txt:
+  Policy CMP0210 is not set: CMAKE_<LANG>_LINK_FLAGS adds link flags to all
+  target types\.  Run "cmake --help-policy CMP0210" for policy details\.  Use
+  the cmake_policy command to set the policy and suppress this warning\.
+
+  For compatibility with older versions of CMake, CMAKE_CXX_LINK_FLAGS will
+  be ignored for all non-EXECUTABLE targets which use these flags.
 This warning is for project developers\.  Use -Wno-dev to suppress it\.

Tests/RunCMake/LinkFlags/CMAKE_LANG_LINK_FLAGS-CMP0210-WARN.cmake

@@ -1,3 +1,8 @@
-set(CMAKE_C_LINK_FLAGS ${pre}BADFLAG${obj})
-add_library(LinkFlags_shared SHARED LinkFlagsLib.c)
-add_executable(LinkFlags_exe LinkFlagsExe.c)
+set(CMAKE_C_LINK_FLAGS ${pre}BADFLAG_C${obj})
+set(CMAKE_CXX_LINK_FLAGS ${pre}BADFLAG_CXX${obj})
+
+add_library(LinkFlags_shared_C SHARED LinkFlagsLib.c)
+add_executable(LinkFlags_exe_C LinkFlagsExe.c)
+
+add_library(LinkFlags_shared_CXX SHARED LinkFlagsLib.cxx)
+add_executable(LinkFlags_exe_CXX LinkFlagsExe.cxx)

Tests/RunCMake/LinkFlags/RunCMakeTest.cmake

@@ -65,8 +65,10 @@ if (NOT CMAKE_C_COMPILER_ID STREQUAL "Intel")
     run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-OLD exe)
 
     run_cmake(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN)
-    run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN shared)
-    run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN exe)
+    run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN shared_C)
+    run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN exe_C)
+    run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN shared_CXX)
+    run_cmake_target(CMAKE_LANG_LINK_FLAGS-CMP0210-WARN exe_CXX)
   endif()
 
   unset(RunCMake_TEST_OPTIONS)