ENH: Re-enable system include dir suppression

This creates variable CMAKE_<LANG>_IMPLICIT_INCLUDE_DIRECTORIES to
specify implicit include directories on a per-language basis.  This
replaces the previous platform-wide variable.  It is necessary to
avoid explicit specification of -I/usr/include on some compilers
(such as HP aCC) because:

  1.) It may break ordering among system include directories defined
      internally by the compiler, thus getting wrong system headers.
  2.) It tells the compiler to treat the system include directory
      as a user include directory, enabling warnings in the headers.

See issue #8598.

1 files changed, 22 insertions, 0 deletions

diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index b2788ae..70e5760 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1186,6 +1186,23 @@ const char* cmLocalGenerator::GetIncludeFlags(const char* lang)
     {
     return this->LanguageToIncludeFlags[lang].c_str();
     }
+
+  // Load implicit include directories for this language.
+  std::set<cmStdString> impDirs;
+  std::string impDirVar = "CMAKE_";
+  impDirVar += lang;
+  impDirVar += "_IMPLICIT_INCLUDE_DIRECTORIES";
+  if(const char* value = this->Makefile->GetDefinition(impDirVar.c_str()))
+    {
+    std::vector<std::string> impDirVec;
+    cmSystemTools::ExpandListArgument(value, impDirVec);
+    for(std::vector<std::string>::const_iterator i = impDirVec.begin();
+        i != impDirVec.end(); ++i)
+      {
+      impDirs.insert(*i);
+      }
+    }
+
   cmOStringStream includeFlags;
   std::vector<std::string> includes;
   this->GetIncludeDirectories(includes);
@@ -1233,6 +1250,11 @@ const char* cmLocalGenerator::GetIncludeFlags(const char* lang)
 #endif
   for(i = includes.begin(); i != includes.end(); ++i)
     {
+    // Skip implicit include directories.
+    if(impDirs.find(*i) != impDirs.end())
+      {
+      continue;
+      }
 #ifdef __APPLE__
     if(cmSystemTools::IsPathToFramework(i->c_str()))
       {