From 1d3308156e1fc1646873b22317265c61288e9e42 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Fri, 27 Feb 2009 11:23:14 -0500
Subject: ENH: Enforce unique binary directories

The second argument of add_subdirectory must name a unique binary
directory or the build files will clobber each other.  This enforces
uniqueness with an error message.
---
 Source/cmGlobalGenerator.cxx |  4 ++++
 Source/cmGlobalGenerator.h   |  9 +++++++++
 Source/cmMakefile.cxx        | 15 +++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index 4fc26f6..0103a85 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -732,18 +732,22 @@ void cmGlobalGenerator::Configure()
   this->ProjectMap.clear();
   this->RuleHashes.clear();
   this->DirectoryContentMap.clear();
+  this->BinaryDirectories.clear();
 
   // start with this directory
   cmLocalGenerator *lg = this->CreateLocalGenerator();
   this->LocalGenerators.push_back(lg);
 
   // set the Start directories
+  cmMakefile* mf = lg->GetMakefile();
   lg->GetMakefile()->SetStartDirectory
     (this->CMakeInstance->GetStartDirectory());
   lg->GetMakefile()->SetStartOutputDirectory
     (this->CMakeInstance->GetStartOutputDirectory());
   lg->GetMakefile()->MakeStartDirectoriesCurrent();
 
+  this->BinaryDirectories.insert(mf->GetStartOutputDirectory());
+
   // now do it
   lg->Configure();
 
diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index 02e2396..2d8ffb6 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -253,6 +253,12 @@ public:
   void AddRuleHash(const std::vector<std::string>& outputs,
                    std::string const& content);
 
+  /** Return whether the given binary directory is unused.  */
+  bool BinaryDirectoryIsNew(const char* dir)
+    {
+    return this->BinaryDirectories.insert(dir).second;
+    }
+
 protected:
   // for a project collect all its targets by following depend
   // information, and also collect all the targets
@@ -350,6 +356,9 @@ private:
       derived(dc), LoadedFromDisk(dc.LoadedFromDisk) {}
   };
   std::map<cmStdString, DirectoryContent> DirectoryContentMap;
+
+  // Set of binary directories on disk.
+  std::set<cmStdString> BinaryDirectories;
 };
 
 #endif
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 3a8ab2a..d22cebd 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -1536,6 +1536,21 @@ void cmMakefile::AddSubDirectory(const char* srcPath, const char *binPath,
       }
     }
 
+  // Make sure the binary directory is unique.
+  cmGlobalGenerator* gg = this->LocalGenerator->GetGlobalGenerator();
+  if(!gg->BinaryDirectoryIsNew(binPath))
+    {
+    cmOStringStream e;
+    e << "The binary directory\n"
+      << "  " << binPath << "\n"
+      << "is already used to build another source directory, so it cannot "
+      << "be used to build source directory\n"
+      << "  " << srcPath << "\n"
+      << "Specify a unique binary directory name.";
+    this->IssueMessage(cmake::FATAL_ERROR, e.str());
+    return;
+    }
+
   // create a new local generator and set its parent
   cmLocalGenerator *lg2 =
     this->LocalGenerator->GetGlobalGenerator()->CreateLocalGenerator();
-- 
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