From fd62a7cac44ba95468767dd0f9b000da6d664b8d Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Mon, 24 Aug 2009 09:54:27 -0400
Subject: [PATCH] Create GLOBAL_DEPENDS_NO_CYCLES property

This global property disallows cycles in the inter-target dependency
graph even among STATIC libraries.  See issue #9444.
---
 Source/cmComputeTargetDepends.cxx | 20 ++++++++++++++++++--
 Source/cmComputeTargetDepends.h   |  1 +
 Source/cmake.cxx                  | 10 ++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/Source/cmComputeTargetDepends.cxx b/Source/cmComputeTargetDepends.cxx
index 7a6e81ffa..12d56968a 100644
--- a/Source/cmComputeTargetDepends.cxx
+++ b/Source/cmComputeTargetDepends.cxx
@@ -103,6 +103,7 @@ cmComputeTargetDepends::cmComputeTargetDepends(cmGlobalGenerator* gg)
   this->GlobalGenerator = gg;
   cmake* cm = this->GlobalGenerator->GetCMakeInstance();
   this->DebugMode = cm->GetPropertyAsBool("GLOBAL_DEPENDS_DEBUG_MODE");
+  this->NoCycles = cm->GetPropertyAsBool("GLOBAL_DEPENDS_NO_CYCLES");
 }
 
 //----------------------------------------------------------------------------
@@ -344,6 +345,13 @@ cmComputeTargetDepends
       continue;
       }
 
+    // Immediately complain if no cycles are allowed at all.
+    if(this->NoCycles)
+      {
+      this->ComplainAboutBadComponent(ccg, c);
+      return false;
+      }
+
     // Make sure the component is all STATIC_LIBRARY targets.
     for(NodeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni)
       {
@@ -391,8 +399,16 @@ cmComputeTargetDepends
         }
       }
     }
-  e << "At least one of these targets is not a STATIC_LIBRARY.  "
-    << "Cyclic dependencies are allowed only among static libraries.";
+  if(this->NoCycles)
+    {
+    e << "The GLOBAL_DEPENDS_NO_CYCLES global property is enabled, so "
+      << "cyclic dependencies are not allowed even among static libraries.";
+    }
+  else
+    {
+    e << "At least one of these targets is not a STATIC_LIBRARY.  "
+      << "Cyclic dependencies are allowed only among static libraries.";
+    }
   cmSystemTools::Error(e.str().c_str());
 }
 
diff --git a/Source/cmComputeTargetDepends.h b/Source/cmComputeTargetDepends.h
index e3e15e190..da29aa160 100644
--- a/Source/cmComputeTargetDepends.h
+++ b/Source/cmComputeTargetDepends.h
@@ -54,6 +54,7 @@ private:
 
   cmGlobalGenerator* GlobalGenerator;
   bool DebugMode;
+  bool NoCycles;
 
   // Collect all targets.
   std::vector<cmTarget*> Targets;
diff --git a/Source/cmake.cxx b/Source/cmake.cxx
index ea36c0b07..dcc3d5035 100644
--- a/Source/cmake.cxx
+++ b/Source/cmake.cxx
@@ -3414,6 +3414,16 @@ void cmake::DefineProperties(cmake *cm)
     "at the beginning of native build system generation.  "
     "This property causes it to display details of its analysis to stderr.");
 
+  cm->DefineProperty(
+    "GLOBAL_DEPENDS_NO_CYCLES", cmProperty::GLOBAL,
+    "Disallow global target dependency graph cycles.",
+    "CMake automatically analyzes the global inter-target dependency graph "
+    "at the beginning of native build system generation.  "
+    "It reports an error if the dependency graph contains a cycle that "
+    "does not consist of all STATIC library targets.  "
+    "This property tells CMake to disallow all cycles completely, even "
+    "among static libraries.");
+
   cm->DefineProperty(
     "ALLOW_DUPLICATE_CUSTOM_TARGETS", cmProperty::GLOBAL,
     "Allow duplicate custom targets to be created.",