ENH: Restored APPEND option to EXPORT() command in new implementation.

Source/cmExportBuildFileGenerator.h

@@ -35,6 +35,8 @@ public:
   void SetExports(std::vector<cmTarget*> const* exports)
     { this->Exports = exports; }
 
+  /** Set whether to append generated code to the output file.  */
+  void SetAppendMode(bool append) { this->AppendMode = append; }
 protected:
   // Implement virtual methods from the superclass.
   virtual bool GenerateMainFile(std::ostream& os);

Source/cmExportCommand.cxx

@@ -26,6 +26,7 @@ cmExportCommand::cmExportCommand()
 :cmCommand()
 ,ArgumentGroup()
 ,Targets(&Helper, "TARGETS")
+,Append(&Helper, "APPEND", &ArgumentGroup)
 ,Namespace(&Helper, "NAMESPACE", &ArgumentGroup)
 ,Filename(&Helper, "FILE", &ArgumentGroup)
 {
@@ -146,6 +147,7 @@ bool cmExportCommand
   cmExportBuildFileGenerator ebfg;
   ebfg.SetExportFile(fname.c_str());
   ebfg.SetNamespace(this->Namespace.GetCString());
+  ebfg.SetAppendMode(this->Append.IsEnabled());
   ebfg.SetExports(&targets);
 
   // Compute the set of configurations exported.

Source/cmExportCommand.h

@@ -65,7 +65,7 @@ public:
     {
     return
       "  export(TARGETS [target1 [target2 [...]]] [NAMESPACE <namespace>]\n"
-      "         FILE <filename>)\n"
+      "         [APPEND] FILE <filename>)\n"
       "Create a file <filename> that may be included by outside projects to "
       "import targets from the current project's build tree.  "
       "This is useful during cross-compiling to build utility executables "
@@ -73,6 +73,8 @@ public:
       "them into another project being compiled for the target platform.  "
       "If the NAMESPACE option is given the <namespace> string will be "
       "prepended to all target names written to the file.  "
+      "If the APPEND option is given the generated code will be appended "
+      "to the file instead of overwriting it.  "
       "If a library target is included in the export but "
       "a target to which it links is not included the behavior is "
       "unspecified."
@@ -88,6 +90,7 @@ public:
 private:
   cmCommandArgumentGroup ArgumentGroup;
   cmCAStringVector Targets;
+  cmCAEnabler Append;
   cmCAString Namespace;
   cmCAString Filename;
 };

Source/cmExportFileGenerator.cxx

@@ -21,6 +21,14 @@
 #include "cmSystemTools.h"
 #include "cmTarget.h"
 
+#include <cmsys/auto_ptr.hxx>
+
+//----------------------------------------------------------------------------
+cmExportFileGenerator::cmExportFileGenerator()
+{
+  this->AppendMode = false;
+}
+
 //----------------------------------------------------------------------------
 void cmExportFileGenerator::AddConfiguration(const char* config)
 {
@@ -43,8 +51,23 @@ void cmExportFileGenerator::SetExportFile(const char* mainFile)
 bool cmExportFileGenerator::GenerateImportFile()
 {
   // Open the output file to generate it.
-  cmGeneratedFileStream exportFileStream(this->MainImportFile.c_str(), true);
+  cmsys::auto_ptr<std::ofstream> foutPtr;
-  if(!exportFileStream)
+  if(this->AppendMode)
+    {
+    // Open for append.
+    cmsys::auto_ptr<std::ofstream>
+      ap(new std::ofstream(this->MainImportFile.c_str(), std::ios::app));
+    foutPtr = ap;
+    }
+  else
+    {
+    // Generate atomically and with copy-if-different.
+    cmsys::auto_ptr<cmGeneratedFileStream>
+      ap(new cmGeneratedFileStream(this->MainImportFile.c_str(), true));
+    ap->SetCopyIfDifferent(true);
+    foutPtr = ap;
+    }
+  if(!foutPtr.get() || !*foutPtr)
     {
     std::string se = cmSystemTools::GetLastSystemError();
     cmOStringStream e;
@@ -53,7 +76,7 @@ bool cmExportFileGenerator::GenerateImportFile()
     cmSystemTools::Error(e.str().c_str());
     return false;
     }
-  std::ostream& os = exportFileStream;
+  std::ostream& os = *foutPtr;
 
   // Start with the import file header.
   this->GenerateImportHeaderCode(os);

Source/cmExportFileGenerator.h

@@ -30,6 +30,7 @@
 class cmExportFileGenerator
 {
 public:
+  cmExportFileGenerator();
   virtual ~cmExportFileGenerator() {}
 
   /** Set the full path to the export file to generate.  */
@@ -90,6 +91,7 @@ protected:
   std::string FileDir;
   std::string FileBase;
   std::string FileExt;
+  bool AppendMode;
 
   // The set of targets included in the export.
   std::set<cmTarget*> ExportedTargets;

Tests/ExportImport/Export/CMakeLists.txt

@@ -31,7 +31,11 @@ install(
 install(EXPORT exp NAMESPACE exp_ DESTINATION lib/exp)
 
 # Export from build tree.
-export(TARGETS testExe1 testLib1 testLib2 testExe2 testLib3 testLib4
+export(TARGETS testExe1 testLib1 testLib2
   NAMESPACE bld_
   FILE ExportBuildTree.cmake
   )
+export(TARGETS testExe2 testLib3 testLib4
+  NAMESPACE bld_
+  APPEND FILE ExportBuildTree.cmake
+  )