Genex: Only evaluate TARGET_OBJECTS to determine target sources.

The output of this expression may contain macros for IDEs to replace
such as $(Configuration), $(CURRENT_ARCH) etc.  To avoid generating
content which is not usable in other contexts, report an error if
there is an attempt to use it in other contexts.

This commit may be reverted in the future if a solution to the
above difference is implemented.

Help/manual/cmake-generator-expressions.7.rst

@@ -190,4 +190,6 @@ property is non-empty::
   Content of ``...`` converted to a C identifier.
 ``$<TARGET_OBJECTS:objLib>``
   List of objects resulting from build of ``objLib``. ``objLib`` must be an
-  object of type ``OBJECT_LIBRARY``.
+  object of type ``OBJECT_LIBRARY``.  This expression may only be used in
+  the sources of :command:`add_library` and :command:`add_executable`
+  commands.

Help/release/dev/file-GENERATE-TARGET_OBJECTS.rst

@@ -1,6 +0,0 @@
-file-GENERATE-TARGET_OBJECTS
-----------------------------
-
-* The :command:`file(GENERATE)` subcommand learned to evaluate the
-  ``TARGET_OBJECTS``
-  :manual:`generator expression <cmake-generator-expressions(7)>`.

Source/cmGeneratorExpression.cxx

@@ -90,6 +90,7 @@ const char *cmCompiledGeneratorExpression::Evaluate(
   context.HadError = false;
   context.HadContextSensitiveCondition = false;
   context.HeadTarget = headTarget;
+  context.EvaluateForBuildsystem = this->EvaluateForBuildsystem;
   context.CurrentTarget = currentTarget ? currentTarget : headTarget;
   context.Backtrace = this->Backtrace;
 
@@ -124,7 +125,8 @@ cmCompiledGeneratorExpression::cmCompiledGeneratorExpression(
               cmListFileBacktrace const& backtrace,
               const std::string& input)
   : Backtrace(backtrace), Input(input),
-    HadContextSensitiveCondition(false)
+    HadContextSensitiveCondition(false),
+    EvaluateForBuildsystem(false)
 {
   cmGeneratorExpressionLexer l;
   std::vector<cmGeneratorExpressionToken> tokens =

Source/cmGeneratorExpression.h

@@ -112,6 +112,11 @@ public:
     return this->HadContextSensitiveCondition;
   }
 
+  void SetEvaluateForBuildsystem(bool eval)
+  {
+    this->EvaluateForBuildsystem = eval;
+  }
+
 private:
   cmCompiledGeneratorExpression(cmListFileBacktrace const& backtrace,
               const std::string& input);
@@ -131,6 +136,7 @@ private:
   mutable std::set<std::string> SeenTargetProperties;
   mutable std::string Output;
   mutable bool HadContextSensitiveCondition;
+  bool EvaluateForBuildsystem;
 };
 
 #endif

Source/cmGeneratorExpressionEvaluator.cxx

@@ -1251,6 +1251,16 @@ static const struct TargetObjectsNode : public cmGeneratorExpressionNode
                        const GeneratorExpressionContent *content,
                        cmGeneratorExpressionDAGChecker *) const
   {
+    if (!context->EvaluateForBuildsystem)
+      {
+      cmOStringStream e;
+      e << "The evaluation of the TARGET_OBJECTS generator expression "
+        "is only suitable for consumption by CMake.  It is not suitable "
+        "for writing out elsewhere.";
+      reportError(context, content->GetOriginalExpression(), e.str());
+      return std::string();
+      }
+
     std::string tgtName = parameters.front();
     cmGeneratorTarget* gt =
                 context->Makefile->FindGeneratorTargetToUse(tgtName.c_str());

Source/cmGeneratorExpressionEvaluator.h

@@ -34,6 +34,7 @@ struct cmGeneratorExpressionContext
   bool Quiet;
   bool HadError;
   bool HadContextSensitiveCondition;
+  bool EvaluateForBuildsystem;
 };
 
 struct cmGeneratorExpressionDAGChecker;

Source/cmTarget.cxx

@@ -732,6 +732,7 @@ cmSourceFile* cmTarget::AddSource(const std::string& src)
     this->Makefile->GetBacktrace(lfbt);
     cmGeneratorExpression ge(lfbt);
     cmsys::auto_ptr<cmCompiledGeneratorExpression> cge = ge.Parse(src);
+    cge->SetEvaluateForBuildsystem(true);
     this->Internal->SourceEntries.push_back(
                           new cmTargetInternals::TargetPropertyEntry(cge));
     }

Tests/GeneratorExpression/CMakeLists.txt

@@ -258,17 +258,3 @@ set(CMP0044_TYPE NEW)
 add_subdirectory(CMP0044 ${CMAKE_BINARY_DIR}/CMP0044-NEW)
 set(CMP0044_TYPE OLD)
 add_subdirectory(CMP0044 ${CMAKE_BINARY_DIR}/CMP0044-OLD)
-
-add_library(objlib OBJECT objlib1.c objlib2.c)
-file(GENERATE
-  OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/objlib_files"
-  CONTENT "$<JOIN:$<TARGET_OBJECTS:objlib>,\n>\n"
-)
-add_custom_target(check_object_files ALL
-  COMMAND ${CMAKE_COMMAND}
-    "-DOBJLIB_LISTFILE=${CMAKE_CURRENT_BINARY_DIR}/objlib_files"
-    -DTEST_CONFIGURATION=${CMAKE_BUILD_TYPE}
-    -DEXPECTED_NUM_OBJECTFILES=2
-    -P "${CMAKE_CURRENT_SOURCE_DIR}/check_object_files.cmake"
-  DEPENDS objlib
-)

Tests/GeneratorExpression/check_object_files.cmake

@@ -1,48 +0,0 @@
-
-if (NOT EXISTS ${OBJLIB_LISTFILE})
-  message(SEND_ERROR "Object listing file \"${OBJLIB_LISTFILE}\" not found!")
-endif()
-
-file(STRINGS ${OBJLIB_LISTFILE} objlib_files)
-
-list(LENGTH objlib_files num_objectfiles)
-if (NOT EXPECTED_NUM_OBJECTFILES EQUAL num_objectfiles)
-  message(SEND_ERROR "Unexpected number of entries in object list file (${num_objectfiles} instead of ${EXPECTED_NUM_OBJECTFILES})")
-endif()
-
-foreach(objlib_file ${objlib_files})
-  set(file_exists False)
-  if (EXISTS ${objlib_file})
-    set(file_exists True)
-  endif()
-
-  if (NOT file_exists)
-    if (objlib_file MATCHES ".(CURRENT_ARCH)")
-      string(REPLACE "$(CONFIGURATION)$(EFFECTIVE_PLATFORM_NAME)" "*" config_file "${objlib_file}")
-      string(REPLACE "$(PROJECT_NAME)" "GeneratorExpression" config_file "${config_file}")
-      string(REPLACE "$(CURRENT_ARCH)" "*" config_file "${config_file}")
-      file(GLOB_RECURSE files "${config_file}")
-      list(LENGTH files num_files)
-      if (NOT files)
-        message(SEND_ERROR "Got no files for expression ${config_file}")
-      endif()
-      set(file_exists True)
-    else()
-      foreach(config_macro "$(Configuration)" "$(OutDir)" "$(IntDir)")
-        string(REPLACE "${config_macro}" "${TEST_CONFIGURATION}" config_file "${objlib_file}")
-        list(APPEND attempts ${config_file})
-        if (EXISTS ${config_file})
-          set(file_exists True)
-        endif()
-      endforeach()
-    endif()
-  endif()
-
-  if (NOT file_exists)
-    if(attempts)
-      list(REMOVE_DUPLICATES attempts)
-      set(tried "  Tried ${attempts}")
-    endif()
-    message(SEND_ERROR "File \"${objlib_file}\" does not exist!${tried}")
-  endif()
-endforeach()

Tests/GeneratorExpression/objlib1.c

@@ -1,5 +0,0 @@
-
-void objlib1()
-{
-
-}

Tests/GeneratorExpression/objlib2.c

@@ -1,5 +0,0 @@
-
-void objlib2()
-{
-
-}

Tests/RunCMake/TargetObjects/BadContext-stderr.txt

@@ -0,0 +1,17 @@
+CMake Error at BadContext.cmake:2 \(file\):
+  Error evaluating generator expression:
+
+    \$<TARGET_OBJECTS:NoTarget>
+
+  The evaluation of the TARGET_OBJECTS generator expression is only suitable
+  for consumption by CMake.  It is not suitable for writing out elsewhere.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error:
+  Error evaluating generator expression:
+
+    \$<TARGET_OBJECTS:NoTarget>
+
+  The evaluation of the TARGET_OBJECTS generator expression is only suitable
+  for consumption by CMake.  It is not suitable for writing out elsewhere.

Tests/RunCMake/TargetObjects/NoTarget.cmake → Tests/RunCMake/TargetObjects/BadContext.cmake

@@ -1,2 +1,4 @@
 
 file(GENERATE OUTPUT test_output CONTENT $<TARGET_OBJECTS:NoTarget>)
+
+install(FILES $<TARGET_OBJECTS:NoTarget> DESTINATION objects)

Tests/RunCMake/TargetObjects/NoTarget-stderr.txt

@@ -1,8 +0,0 @@
-CMake Error at NoTarget.cmake:2 \(file\):
-  Error evaluating generator expression:
-
-    \$<TARGET_OBJECTS:NoTarget>
-
-  Objects of target "NoTarget" referenced but no such target exists.
-Call Stack \(most recent call first\):
-  CMakeLists.txt:3 \(include\)

Tests/RunCMake/TargetObjects/NotObjlibTarget-result.txt

@@ -1 +0,0 @@
-1

Tests/RunCMake/TargetObjects/NotObjlibTarget-stderr.txt

@@ -1,8 +0,0 @@
-CMake Error at NotObjlibTarget.cmake:4 \(file\):
-  Error evaluating generator expression:
-
-    \$<TARGET_OBJECTS:StaticLib>
-
-  Objects of target "StaticLib" referenced but is not an OBJECT library.
-Call Stack \(most recent call first\):
-  CMakeLists.txt:3 \(include\)

Tests/RunCMake/TargetObjects/NotObjlibTarget.cmake

@@ -1,4 +0,0 @@
-
-add_library(StaticLib empty.cpp)
-
-file(GENERATE OUTPUT test_output CONTENT $<TARGET_OBJECTS:StaticLib>)

Tests/RunCMake/TargetObjects/RunCMakeTest.cmake

@@ -1,4 +1,3 @@
 include(RunCMake)
 
-run_cmake(NoTarget)
-run_cmake(NotObjlibTarget)
+run_cmake(BadContext)

Tests/RunCMake/TargetObjects/empty.cpp

@@ -1,7 +0,0 @@
-#ifdef _WIN32
-__declspec(dllexport)
-#endif
-int empty()
-{
-  return 0;
-}