Add AddSymbol() method to DynamicLibrary to work around Windows limitation

of being unable to search for symbols in an EXE.  It will also allow other
existing hacks to be improved.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25805 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/System/DynamicLibrary.h

@@ -26,6 +26,9 @@ namespace sys {
   /// operating system interface, this class provides a portable interface that
   /// allows dynamic libraries to be loaded and and searched for externally
   /// defined symbols. This is typically used to provide "plug-in" support.
+  /// It also allows for symbols to be defined which don't live in any library,
+  /// but rather the main program itself, useful on Windows where the main
+  /// executable cannot be searched.
   /// @since 1.4
   /// @brief Portable dynamic library abstraction.
   class DynamicLibrary {
@@ -81,6 +84,17 @@ namespace sys {
         return SearchForAddressOfSymbol(symbolName.c_str());
       }
 
+      /// This functions permanently adds the symbol \p symbolName with the
+      /// value \p symbolValue.  These symbols are searched before any
+      /// libraries.
+      /// @brief Add searchable symbol/value pair.
+      static void AddSymbol(const char* symbolName, void *symbolValue);
+
+      /// @brief Convenience function for C++ophiles.
+      static void AddSymbol(const std::string& symbolName, void *symbolValue) {
+        AddSymbol(symbolName.c_str(), symbolValue);
+      }
+
     /// @}
     /// @name Accessors
     /// @{

lib/System/DynamicLibrary.cpp

@@ -13,6 +13,14 @@
 
 #include "llvm/System/DynamicLibrary.h"
 #include "llvm/Config/config.h"
+#include <map>
+
+// Collection of symbol name/value pairs to be searched prior to any libraries.
+static std::map<std::string, void *> g_symbols;
+
+void llvm::sys::DynamicLibrary::AddSymbol(const char* symbolName, void *symbolValue) {
+  g_symbols[symbolName] = symbolValue;
+}
 
 // It is not possible to use ltdl.c on VC++ builds as the terms of its LGPL
 // license and special exception would cause all of LLVM to be placed under
@@ -107,6 +115,13 @@ void DynamicLibrary::LoadLibraryPermanently(const char* filename) {
 
 void* DynamicLibrary::SearchForAddressOfSymbol(const char* symbolName) {
   check_ltdl_initialization();
+
+  // First check symbols added via AddSymbol().
+  std::map<std::string, void *>::iterator I = g_symbols.find(symbolName);
+  if (I != g_symbols.end())
+    return I->second;
+
+  // Now search the libraries.
   for (std::vector<lt_dlhandle>::iterator I = OpenedHandles.begin(),
        E = OpenedHandles.end(); I != E; ++I) {
     lt_ptr ptr = lt_dlsym(*I, symbolName);

lib/System/Win32/DynamicLibrary.inc

@@ -107,6 +107,12 @@ void DynamicLibrary::LoadLibraryPermanently(const char* filename) {
 }
 
 void* DynamicLibrary::SearchForAddressOfSymbol(const char* symbolName) {
+  // First check symbols added via AddSymbol().
+  std::map<std::string, void *>::iterator I = g_symbols.find(symbolName);
+  if (I != g_symbols.end())
+    return I->second;
+
+  // Now search the libraries.
   for (std::vector<HMODULE>::iterator I = OpenedHandles.begin(),
        E = OpenedHandles.end(); I != E; ++I) {
     FARPROC ptr = GetProcAddress((HMODULE)*I, symbolName);