Export: Report error on relative include with genex.

Diagnostics which check the sanity of exported include paths
previously skipped over any path containing a generator expression.

Introduce a policy to issue an error message in such cases.

The export files created in the OLD behavior are not usable, because
they contain relative paths or paths to the source or build location
which are not suitable for use on installation. CMake will report an
error on import.

4 files changed, 36 insertions, 15 deletions

diff --git a/Source/cmExportFileGenerator.cxx b/Source/cmExportFileGenerator.cxx
index 9186ab6..2d963fe 100644
--- a/Source/cmExportFileGenerator.cxx
+++ b/Source/cmExportFileGenerator.cxx
@@ -233,26 +233,46 @@ static bool checkInterfaceDirs(const std::string &prepro,
 
   const bool inSourceBuild = strcmp(topSourceDir, topBinaryDir) == 0;
 
+  bool hadFatalError = false;
+
   for(std::vector<std::string>::iterator li = parts.begin();
       li != parts.end(); ++li)
     {
-    if (cmGeneratorExpression::Find(*li) != std::string::npos)
+    size_t genexPos = cmGeneratorExpression::Find(*li);
+    if (genexPos == 0)
       {
       continue;
       }
+    cmake::MessageType messageType = cmake::FATAL_ERROR;
+    cmOStringStream e;
+    if (genexPos != std::string::npos)
+      {
+      switch (target->GetPolicyStatusCMP0041())
+        {
+        case cmPolicies::WARN:
+          messageType = cmake::WARNING;
+          e << target->GetMakefile()->GetPolicies()
+                      ->GetPolicyWarning(cmPolicies::CMP0041) << "\n";
+          break;
+        case cmPolicies::OLD:
+          continue;
+        case cmPolicies::REQUIRED_IF_USED:
+        case cmPolicies::REQUIRED_ALWAYS:
+        case cmPolicies::NEW:
+          hadFatalError = true;
+          break; // Issue fatal message.
+        }
+      }
     if (cmHasLiteralPrefix(li->c_str(), "${_IMPORT_PREFIX}"))
       {
       continue;
       }
     if (!cmSystemTools::FileIsFullPath(li->c_str()))
       {
-      cmOStringStream e;
       e << "Target \"" << target->GetName() << "\" "
            "INTERFACE_INCLUDE_DIRECTORIES property contains relative path:\n"
            "  \"" << *li << "\"";
-      target->GetMakefile()->IssueMessage(cmake::FATAL_ERROR,
-                                          e.str().c_str());
-      return false;
+      target->GetMakefile()->IssueMessage(messageType, e.str().c_str());
       }
     if (isSubDirectory(li->c_str(), installDir))
       {
@@ -260,29 +280,23 @@ static bool checkInterfaceDirs(const std::string &prepro,
       }
     if (isSubDirectory(li->c_str(), topBinaryDir))
       {
-      cmOStringStream e;
       e << "Target \"" << target->GetName() << "\" "
            "INTERFACE_INCLUDE_DIRECTORIES property contains path:\n"
            "  \"" << *li << "\"\nwhich is prefixed in the build directory.";
-      target->GetMakefile()->IssueMessage(cmake::FATAL_ERROR,
-                                          e.str().c_str());
-      return false;
+      target->GetMakefile()->IssueMessage(messageType, e.str().c_str());
       }
     if (!inSourceBuild)
       {
       if (isSubDirectory(li->c_str(), topSourceDir))
         {
-        cmOStringStream e;
         e << "Target \"" << target->GetName() << "\" "
             "INTERFACE_INCLUDE_DIRECTORIES property contains path:\n"
             "  \"" << *li << "\"\nwhich is prefixed in the source directory.";
-        target->GetMakefile()->IssueMessage(cmake::FATAL_ERROR,
-                                            e.str().c_str());
-        return false;
+        target->GetMakefile()->IssueMessage(messageType, e.str().c_str());
         }
       }
     }
-  return true;
+  return !hadFatalError;
 }
 
 //----------------------------------------------------------------------------
diff --git a/Source/cmPolicies.cxx b/Source/cmPolicies.cxx
index b9b469c..0b3018e 100644
--- a/Source/cmPolicies.cxx
+++ b/Source/cmPolicies.cxx
@@ -306,6 +306,11 @@ cmPolicies::cmPolicies()
     CMP0040, "CMP0040",
     "The target in the TARGET signature of add_custom_command() must exist.",
     3,0,0,0, cmPolicies::WARN);
+
+  this->DefinePolicy(
+    CMP0041, "CMP0041",
+    "Error on relative include with generator expression.",
+    3,0,0,0, cmPolicies::WARN);
 }
 
 cmPolicies::~cmPolicies()
diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index 6834121..245ec4b 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -94,6 +94,7 @@ public:
     CMP0039, ///< Utility targets may not have link dependencies
     CMP0040, ///< The target in the TARGET signature of
     /// add_custom_command() must exist.
+    CMP0041, ///< Error on relative include with generator expression
 
     /** \brief Always the last entry.
      *
diff --git a/Source/cmTarget.h b/Source/cmTarget.h
index 35ec680..7a40d70 100644
--- a/Source/cmTarget.h
+++ b/Source/cmTarget.h
@@ -25,7 +25,8 @@
   F(CMP0008) \
   F(CMP0020) \
   F(CMP0021) \
-  F(CMP0022)
+  F(CMP0022) \
+  F(CMP0041)
 
 class cmake;
 class cmMakefile;