Disallow link-to-self (#13947).

Help/manual/cmake-policies.7.rst

@@ -71,3 +71,4 @@ All Policies
    /policy/CMP0035
    /policy/CMP0036
    /policy/CMP0037
+   /policy/CMP0038

Help/policy/CMP0038.rst

@@ -0,0 +1,16 @@
+CMP0038
+-------
+
+Targets may not link directly to themselves
+
+CMake 2.8.12 and lower allowed a build target to link to itself directly with
+a :command:`target_link_libraries` call. This is an indicator of a bug in
+user code.
+
+The OLD behavior for this policy is to ignore targets which list themselves
+in their own link implementation.  The NEW behavior for this policy is to
+report an error if a target attempts to link to itself.
+
+This policy was introduced in CMake version 3.0.0.  CMake version
+|release| warns when the policy is not set and uses OLD behavior.  Use
+the cmake_policy command to set it to OLD or NEW explicitly.

Source/cmPolicies.cxx

@@ -291,6 +291,11 @@ cmPolicies::cmPolicies()
     CMP0037, "CMP0037",
     "Target names should match a validity pattern.",
     3,0,0,0, cmPolicies::WARN);
+
+  this->DefinePolicy(
+    CMP0038, "CMP0038",
+    "Targets may not link directly to themselves.",
+    3,0,0,0, cmPolicies::WARN);
 }
 
 cmPolicies::~cmPolicies()

Source/cmPolicies.h

@@ -89,6 +89,7 @@ public:
     CMP0035, ///< Disallow command: variable_requires
     CMP0036, ///< Disallow command: build_name
     CMP0037, ///< Target names should match a validity pattern.
+    CMP0038, ///< Targets may not link directly to themselves
 
     /** \brief Always the last entry.
      *

Source/cmTarget.cxx

@@ -932,12 +932,6 @@ void cmTarget::AddLinkLibrary(cmMakefile& mf,
                               const char *target, const char* lib,
                               LinkLibraryType llt)
 {
-  // Never add a self dependency, even if the user asks for it.
-  if(strcmp( target, lib ) == 0)
-    {
-    return;
-    }
-
   cmTarget *tgt = this->Makefile->FindTargetToUse(lib);
   {
   const bool isNonImportedTarget = tgt && !tgt->IsImported();
@@ -951,7 +945,8 @@ void cmTarget::AddLinkLibrary(cmMakefile& mf,
   }
 
   if (cmGeneratorExpression::Find(lib) != std::string::npos
-      || (tgt && tgt->GetType() == INTERFACE_LIBRARY))
+      || (tgt && tgt->GetType() == INTERFACE_LIBRARY)
+      || (strcmp( target, lib ) == 0))
     {
     return;
     }
@@ -5293,6 +5288,41 @@ void cmTarget::ComputeLinkImplementation(const char* config,
     std::string item = this->CheckCMP0004(*li);
     if(item == this->GetName() || item.empty())
       {
+      if(item == this->GetName())
+        {
+        bool noMessage = false;
+        cmake::MessageType messageType = cmake::FATAL_ERROR;
+        cmOStringStream e;
+        switch(this->Makefile->GetPolicyStatus(cmPolicies::CMP0038))
+          {
+          case cmPolicies::WARN:
+            {
+            e << (this->Makefile->GetPolicies()
+                  ->GetPolicyWarning(cmPolicies::CMP0038)) << "\n";
+            messageType = cmake::AUTHOR_WARNING;
+            }
+            break;
+          case cmPolicies::OLD:
+            noMessage = true;
+          case cmPolicies::REQUIRED_IF_USED:
+          case cmPolicies::REQUIRED_ALWAYS:
+          case cmPolicies::NEW:
+            // Issue the fatal message.
+            break;
+          }
+
+        if(!noMessage)
+          {
+          e << "Target \"" << this->GetName() << "\" links to itself.";
+          this->Makefile->GetCMakeInstance()->IssueMessage(messageType,
+                                                        e.str(),
+                                                        this->GetBacktrace());
+          if (messageType == cmake::FATAL_ERROR)
+            {
+            return;
+            }
+          }
+        }
       continue;
       }
     cmTarget *tgt = this->Makefile->FindTargetToUse(li->c_str());
@@ -5335,6 +5365,7 @@ void cmTarget::ComputeLinkImplementation(const char* config,
           }
         }
       }
+
     // The entry is meant for this configuration.
     impl.Libraries.push_back(item);
     }

Tests/RunCMake/CMP0038/CMP0038-NEW-result.txt

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

Tests/RunCMake/CMP0038/CMP0038-NEW-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at CMP0038-NEW.cmake:3 \(add_library\):
+  Target "self_link" links to itself.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/CMP0038/CMP0038-NEW.cmake

@@ -0,0 +1,4 @@
+
+cmake_policy(SET CMP0038 NEW)
+add_library(self_link empty.cpp)
+target_link_libraries(self_link self_link)

Tests/RunCMake/CMP0038/CMP0038-OLD-result.txt

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

Tests/RunCMake/CMP0038/CMP0038-OLD-stderr.txt

@@ -0,0 +1 @@
+^$

Tests/RunCMake/CMP0038/CMP0038-OLD.cmake

@@ -0,0 +1,4 @@
+
+cmake_policy(SET CMP0038 OLD)
+add_library(self_link empty.cpp)
+target_link_libraries(self_link self_link)

Tests/RunCMake/CMP0038/CMP0038-WARN-result.txt

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

Tests/RunCMake/CMP0038/CMP0038-WARN-stderr.txt

@@ -0,0 +1,9 @@
+CMake Warning \(dev\) at CMP0038-WARN.cmake:2 \(add_library\):
+  Policy CMP0038 is not set: Targets may not link directly to themselves.
+  Run "cmake --help-policy CMP0038" for policy details.  Use the cmake_policy
+  command to set the policy and suppress this warning.
+
+  Target "self_link" links to itself.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.

Tests/RunCMake/CMP0038/CMP0038-WARN.cmake

@@ -0,0 +1,3 @@
+
+add_library(self_link empty.cpp)
+target_link_libraries(self_link self_link)

Tests/RunCMake/CMP0038/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 2.8.12)
+project(${RunCMake_TEST} CXX)
+include(${RunCMake_TEST}.cmake NO_POLICY_SCOPE)

Tests/RunCMake/CMP0038/RunCMakeTest.cmake

@@ -0,0 +1,5 @@
+include(RunCMake)
+
+run_cmake(CMP0038-WARN)
+run_cmake(CMP0038-NEW)
+run_cmake(CMP0038-OLD)

Tests/RunCMake/CMP0038/empty.cpp

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

Tests/RunCMake/CMakeLists.txt

@@ -59,6 +59,7 @@ add_RunCMake_test(CMP0028)
 if (NOT "${CMAKE_TEST_GENERATOR}" MATCHES "(MSYS|MinGW|NMake|Borland) Makefiles")
   add_RunCMake_test(CMP0037)
 endif()
+add_RunCMake_test(CMP0038)
 add_RunCMake_test(CTest)
 if(UNIX AND "${CMAKE_TEST_GENERATOR}" MATCHES "Unix Makefiles")
   add_RunCMake_test(CompilerChange)