OS X: Detect implicit linker framework search paths

Previously we hard-coded a list of implicit framework directories but
did not account for CMAKE_OSX_SYSROOT or for changes to the list across
OS X versions.  Instead we should automatically detect the framework
directories for the active toolchain.

The parent commit added the "-Wl,-v" option to ask "ld" to print its
implicit directories.  It displays a block such as:

 Framework search paths:
	/...

Parse this block to extract the list of framework directories.

Detection may fail on toolchains that do not list their framework
directories, such as older OS X linkers.  Always treat the paths

 <sdk>/Library/Frameworks
 <sdk>/System/Library/Frameworks
 <sdk>/Network/Library/Frameworks # Older OS X only
 /System/Library/Frameworks

as implicit.  Note that /System/Library/Frameworks should always be
considered implicit so that frameworks CMake finds there will not
override the SDK copies.

1 files changed, 25 insertions, 4 deletions

diff --git a/Source/cmComputeLinkInformation.cxx b/Source/cmComputeLinkInformation.cxx
index d8ffb5e..19de903 100644
--- a/Source/cmComputeLinkInformation.cxx
+++ b/Source/cmComputeLinkInformation.cxx
@@ -1376,10 +1376,31 @@ void cmComputeLinkInformation::DropDirectoryItem(std::string const& item)
 //----------------------------------------------------------------------------
 void cmComputeLinkInformation::ComputeFrameworkInfo()
 {
-  // Avoid adding system framework paths.  See "man ld" on OS X.
-  this->FrameworkPathsEmmitted.insert("/Library/Frameworks");
-  this->FrameworkPathsEmmitted.insert("/Network/Library/Frameworks");
-  this->FrameworkPathsEmmitted.insert("/System/Library/Frameworks");
+  // Avoid adding implicit framework paths.
+  std::vector<std::string> implicitDirVec;
+
+  // Get platform-wide implicit directories.
+  if(const char* implicitLinks = this->Makefile->GetDefinition
+     ("CMAKE_PLATFORM_IMPLICIT_LINK_FRAMEWORK_DIRECTORIES"))
+    {
+    cmSystemTools::ExpandListArgument(implicitLinks, implicitDirVec);
+    }
+
+  // Get language-specific implicit directories.
+  std::string implicitDirVar = "CMAKE_";
+  implicitDirVar += this->LinkLanguage;
+  implicitDirVar += "_IMPLICIT_LINK_FRAMEWORK_DIRECTORIES";
+  if(const char* implicitDirs =
+     this->Makefile->GetDefinition(implicitDirVar.c_str()))
+    {
+    cmSystemTools::ExpandListArgument(implicitDirs, implicitDirVec);
+    }
+
+  for(std::vector<std::string>::const_iterator i = implicitDirVec.begin();
+      i != implicitDirVec.end(); ++i)
+    {
+    this->FrameworkPathsEmmitted.insert(*i);
+    }
 
   // Regular expression to extract a framework path and name.
   this->SplitFramework.compile("(.*)/(.*)\\.framework$");