Tolerate cycles in shared library link interfaces (#12647)

Since commit 183b9509 (Follow all dependencies of shared library private
dependencies, 2011-12-14) we honor LINK_INTERFACE_LIBRARIES when
following dependent shared libraries.  The link interface properties may
form a cycle if set incorrectly by a project.  Furthermore, the property
LINK_DEPENDENT_LIBRARIES may form a cycle if set incorrectly by hand
(though CMake should never generate one).  In either case, do not follow
the cycle forever when following the dependent shared library closure.
We only need to add dependency edges to the constraint graph once.

Add "LinkInterfaceLoop" test to cover this case.

1 files changed, 19 insertions, 3 deletions

diff --git a/Source/cmComputeLinkDepends.cxx b/Source/cmComputeLinkDepends.cxx
index 802cfcf..9a075bd 100644
--- a/Source/cmComputeLinkDepends.cxx
+++ b/Source/cmComputeLinkDepends.cxx
@@ -358,7 +358,7 @@ void cmComputeLinkDepends::FollowLinkEntry(BFSEntry const& qe)
       this->AddLinkEntries(depender_index, iface->Libraries);
 
       // Handle dependent shared libraries.
-      this->QueueSharedDependencies(depender_index, iface->SharedDeps);
+      this->FollowSharedDeps(depender_index, iface);
 
       // Support for CMP0003.
       for(std::vector<std::string>::const_iterator
@@ -379,6 +379,23 @@ void cmComputeLinkDepends::FollowLinkEntry(BFSEntry const& qe)
 //----------------------------------------------------------------------------
 void
 cmComputeLinkDepends
+::FollowSharedDeps(int depender_index, cmTarget::LinkInterface const* iface,
+                   bool follow_interface)
+{
+  // Follow dependencies if we have not followed them already.
+  if(this->SharedDepFollowed.insert(depender_index).second)
+    {
+    if(follow_interface)
+      {
+      this->QueueSharedDependencies(depender_index, iface->Libraries);
+      }
+    this->QueueSharedDependencies(depender_index, iface->SharedDeps);
+    }
+}
+
+//----------------------------------------------------------------------------
+void
+cmComputeLinkDepends
 ::QueueSharedDependencies(int depender_index,
                           std::vector<std::string> const& deps)
 {
@@ -430,8 +447,7 @@ void cmComputeLinkDepends::HandleSharedDependency(SharedDepEntry const& dep)
        entry.Target->GetLinkInterface(this->Config))
       {
       // Follow public and private dependencies transitively.
-      this->QueueSharedDependencies(index, iface->Libraries);
-      this->QueueSharedDependencies(index, iface->SharedDeps);
+      this->FollowSharedDeps(index, iface, true);
       }
     }
 }