ENH: Add policy CMP_0004 to require library names to have no leading or trailing whitespace. Replace previous check of CMAKE_BACKWARDS_COMPATIBILITY against version 2.4 with the policy.

Source/cmComputeLinkDepends.cxx

@@ -21,6 +21,7 @@
 #include "cmLocalGenerator.h"
 #include "cmMakefile.h"
 #include "cmTarget.h"
+#include "cmake.h"
 
 #include <cmsys/stl/algorithm>
 
@@ -161,6 +162,7 @@ cmComputeLinkDepends
   this->Makefile = this->Target->GetMakefile();
   this->LocalGenerator = this->Makefile->GetLocalGenerator();
   this->GlobalGenerator = this->LocalGenerator->GetGlobalGenerator();
+  this->CMakeInstance = this->GlobalGenerator->GetCMakeInstance();
 
   // The configuration being linked.
   this->Config = config;
@@ -568,17 +570,45 @@ std::string cmComputeLinkDepends::CleanItemName(std::string const& item)
     {
     lib = lib.substr(0, pos+1);
     }
-  if(lib != item && !this->Makefile->NeedBackwardsCompatibility(2,4))
-    {
-    cmOStringStream e;
-    e << "Target \"" << this->Target->GetName() << "\" links to item \""
-      << item << "\" which has leading or trailing whitespace.  "
-      << "CMake is stripping off the whitespace but this may not be "
-      << "supported in the future.  "
-      << "Update the CMakeLists.txt files to avoid adding the whitespace.  "
-      << "Set CMAKE_BACKWARDS_COMPATIBILITY to 2.4 or lower to disable this "
-      << "warning.";
-    cmSystemTools::Message(e.str().c_str());
+  if(lib != item)
+    {
+    switch(this->Target->GetPolicyStatusCMP0004())
+      {
+      case cmPolicies::WARN:
+        {
+        cmOStringStream w;
+        w << (this->Makefile->GetPolicies()
+              ->GetPolicyWarning(cmPolicies::CMP0004)) << "\n"
+          << "Target \"" << this->Target->GetName() << "\" links to item \""
+          << item << "\" which has leading or trailing whitespace.";
+        this->CMakeInstance->IssueMessage(cmake::AUTHOR_WARNING, w.str(),
+                                          this->Target->GetBacktrace());
+        }
+      case cmPolicies::OLD:
+        break;
+      case cmPolicies::NEW:
+        {
+        cmOStringStream e;
+        e << "Target \"" << this->Target->GetName() << "\" links to item \""
+          << item << "\" which has leading or trailing whitespace.  "
+          << "This is now an error according to policy CMP0004.";
+        this->CMakeInstance->IssueMessage(cmake::FATAL_ERROR, e.str(),
+                                          this->Target->GetBacktrace());
+        }
+        break;
+      case cmPolicies::REQUIRED_IF_USED:
+      case cmPolicies::REQUIRED_ALWAYS:
+        {
+        cmOStringStream e;
+        e << (this->Makefile->GetPolicies()
+              ->GetRequiredPolicyError(cmPolicies::CMP0004)) << "\n"
+          << "Target \"" << this->Target->GetName() << "\" links to item \""
+          << item << "\" which has leading or trailing whitespace.";
+        this->CMakeInstance->IssueMessage(cmake::FATAL_ERROR, e.str(),
+                                          this->Target->GetBacktrace());
+        }
+        break;
+      }
     }
   return lib;
 }

Source/cmComputeLinkDepends.h

@@ -29,6 +29,7 @@ class cmGlobalGenerator;
 class cmLocalGenerator;
 class cmMakefile;
 class cmTarget;
+class cmake;
 
 /** \class cmComputeLinkDepends
  * \brief Compute link dependencies for targets.
@@ -60,6 +61,7 @@ private:
   cmMakefile* Makefile;
   cmLocalGenerator* LocalGenerator;
   cmGlobalGenerator* GlobalGenerator;
+  cmake* CMakeInstance;
   bool DebugMode;
 
   // Configuration information.

Source/cmPolicies.cxx

@@ -200,6 +200,22 @@ cmPolicies::cmPolicies()
     "When all items on the link line have known paths CMake does not check "
     "this policy so it has no effect.",
     2,6,0, cmPolicies::WARN);
+
+  this->DefinePolicy(
+    CMP0004, "CMP0004",
+    "Libraries linked may not have leading or trailing whitespace.",
+    "CMake versions 2.4 and below silently removed leading and trailing "
+    "whitespace from libraries linked with code like\n"
+    "  target_link_libraries(myexe \" A \")\n"
+    "This could lead to subtle errors in user projects.\n"
+    "The OLD behavior for this policy is to silently remove leading and "
+    "trailing whitespace.  "
+    "The NEW behavior for this policy is to diagnose the existence of "
+    "such whitespace as an error.  "
+    "The setting for this policy used when checking the library names is "
+    "that in effect when the target is created by an add_executable or "
+    "add_library command.",
+    2,6,0, cmPolicies::WARN);
 }
 
 cmPolicies::~cmPolicies()

Source/cmPolicies.h

@@ -44,6 +44,7 @@ public:
     CMP0001, // Ignore old compatibility variable
     CMP0002, // Target names must be unique
     CMP0003, // Linking does not include extra -L paths
+    CMP0004, // Libraries linked may not have leading or trailing whitespace
 
     // Always the last entry.  Useful mostly to avoid adding a comma
     // the last policy when adding a new one.

Source/cmTarget.cxx

@@ -54,6 +54,7 @@ cmTarget::cmTarget()
 {
   this->Makefile = 0;
   this->PolicyStatusCMP0003 = cmPolicies::WARN;
+  this->PolicyStatusCMP0004 = cmPolicies::WARN;
   this->LinkLibrariesAnalyzed = false;
   this->HaveInstallRule = false;
   this->DLLPlatform = false;
@@ -731,6 +732,8 @@ void cmTarget::SetMakefile(cmMakefile* mf)
   // Record current policies for later use.
   this->PolicyStatusCMP0003 =
     this->Makefile->GetPolicyStatus(cmPolicies::CMP0003);
+  this->PolicyStatusCMP0004 =
+    this->Makefile->GetPolicyStatus(cmPolicies::CMP0004);
 }
 
 //----------------------------------------------------------------------------

Source/cmTarget.h

@@ -110,6 +110,10 @@ public:
   cmPolicies::PolicyStatus GetPolicyStatusCMP0003() const
     { return this->PolicyStatusCMP0003; }
 
+  /** Get the status of policy CMP0004 when the target was created.  */
+  cmPolicies::PolicyStatus GetPolicyStatusCMP0004() const
+    { return this->PolicyStatusCMP0004; }
+
   /**
    * Get the list of the custom commands for this target
    */
@@ -537,6 +541,7 @@ private:
 
   // Policy status recorded when target was created.
   cmPolicies::PolicyStatus PolicyStatusCMP0003;
+  cmPolicies::PolicyStatus PolicyStatusCMP0004;
 
   // Internal representation details.
   friend class cmTargetInternals;