Reland r296442 with modifications reverted in r296463.

Original commit message:

"Allow externally dlopen-ed libraries to be registered as permanent libraries.

This is also useful in cases when llvm is in a shared library. First we dlopen
the llvm shared library and then we register it as a permanent library in order
to keep the JIT and other services working.

Patch reviewed by Vedant Kumar (D29955)!"

llvm-svn: 296774

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/include/llvm/Support/DynamicLibrary.h b/llvm/include/llvm/Support/DynamicLibrary.h
index a7d22212dbd..eda98b928a6 100644
--- a/llvm/include/llvm/Support/DynamicLibrary.h
+++ b/llvm/include/llvm/Support/DynamicLibrary.h
@@ -14,6 +14,8 @@
 #ifndef LLVM_SUPPORT_DYNAMICLIBRARY_H
 #define LLVM_SUPPORT_DYNAMICLIBRARY_H
 
+#include "llvm/Support/Mutex.h"
+
 #include <string>
 
 namespace llvm {
@@ -68,6 +70,15 @@ namespace sys {
     static DynamicLibrary getPermanentLibrary(const char *filename,
                                               std::string *errMsg = nullptr);
 
+    /// Registers an externally loaded library. The library will be unloaded
+    /// when the program terminates.
+    ///
+    /// It is safe to call this function multiple times for the same library.
+    ///
+    /// \returns An empty \p DynamicLibrary if the library was already loaded.
+    static DynamicLibrary addPermanentLibrary(void *handle,
+                                              std::string *errMsg = nullptr);
+
     /// This function permanently loads the dynamic library at the given path.
     /// Use this instead of getPermanentLibrary() when you won't need to get
     /// symbols from the library itself.