From 92213e719a6c4c83b47ec25928f3edf751d05fcc Mon Sep 17 00:00:00 2001
From: Bertrand Bellenot <bertrand.bellenot@cern.ch>
Date: Wed, 29 Nov 2017 14:17:01 +0100
Subject: [PATCH] Switch object format from ELF to COFF and fix symbols lookup

- Switch object format from ELF (Linux) to COFF (Windows)
- Fix mangled symbols lookup on Windows: remove leading '_' and use malloc to simulate __imp_ variables (that are indirection pointers)
---
 lib/Interpreter/CIFactory.cpp      |  2 +-
 lib/Interpreter/IncrementalJIT.cpp |  4 ++--
 lib/Utils/PlatformWin.cpp          | 30 ++++++++++++++++++++++++++----
 3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/lib/Interpreter/CIFactory.cpp b/lib/Interpreter/CIFactory.cpp
index 15e466cc..2a410ce1 100644
--- a/lib/Interpreter/CIFactory.cpp
+++ b/lib/Interpreter/CIFactory.cpp
@@ -894,7 +894,7 @@ static void stringifyPreprocSetting(PreprocessorOptions& PPOpts,
     llvm::Triple TheTriple(llvm::sys::getProcessTriple());
 #ifdef LLVM_ON_WIN32
     // COFF format currently needs a few changes in LLVM to function properly.
-    TheTriple.setObjectFormat(llvm::Triple::ELF);
+    TheTriple.setObjectFormat(llvm::Triple::COFF);
 #endif
     clang::driver::Driver Drvr(argv[0], TheTriple.getTriple(), *Diags);
     //Drvr.setWarnMissingInput(false);
diff --git a/lib/Interpreter/IncrementalJIT.cpp b/lib/Interpreter/IncrementalJIT.cpp
index 963bbeb4..d6135ad0 100644
--- a/lib/Interpreter/IncrementalJIT.cpp
+++ b/lib/Interpreter/IncrementalJIT.cpp
@@ -16,8 +16,8 @@
 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
 #include "llvm/Support/DynamicLibrary.h"
 
-#ifdef __APPLE__
-// Apple adds an extra '_'
+#if defined(__APPLE__) || defined (_MSC_VER)
+// Apple and Windows add an extra '_'
 # define MANGLE_PREFIX "_"
 #endif
 
diff --git a/lib/Utils/PlatformWin.cpp b/lib/Utils/PlatformWin.cpp
index bec1f3c2..adbf48ec 100644
--- a/lib/Utils/PlatformWin.cpp
+++ b/lib/Utils/PlatformWin.cpp
@@ -533,6 +533,16 @@ const void* DLOpen(const std::string& Path, std::string* Err) {
   return reinterpret_cast<void*>(dyLibHandle);
 }
 
+const void *CheckImp(void *addr, bool dllimp) {
+  // __imp_ variables are indirection pointers, so use malloc to simulate that
+  if (dllimp) {
+    void **imp_addr = (void**)malloc(sizeof(void*));
+    *imp_addr = addr;
+    addr = (void*)imp_addr;
+  }
+  return (const void *)addr;
+}
+
 const void* DLSym(const std::string& Name, std::string* Err) {
  #ifdef _WIN64
   const DWORD Flags = LIST_MODULES_64BIT;
@@ -540,6 +550,18 @@ const void* DLSym(const std::string& Name, std::string* Err) {
   const DWORD Flags = LIST_MODULES_32BIT;
  #endif
 
+  bool dllimp = false;
+  std::string s = Name;
+  // remove the leading '__imp_' from the symbol (will be replaced by an
+  // indirection pointer later on)
+  if (s.compare(0, 6, "__imp_") == 0) {
+    dllimp = true;
+    s.replace(0, 6, "");
+  }
+  // remove the leading '_' from the symbol
+  if (s.compare(0, 1, "_") == 0)
+    s.replace(0, 1, "");
+
   DWORD Bytes;
   std::string ErrStr;
   llvm::SmallVector<HMODULE, 128> Modules;
@@ -554,8 +576,8 @@ const void* DLSym(const std::string& Name, std::string* Err) {
 
     // In reverse so user loaded modules are searched first
     for (auto It = Modules.rbegin(), End = Modules.rend(); It < End; ++It) {
-      if (const void* Addr = ::GetProcAddress(*It, Name.c_str()))
-            return Addr;
+      if (void* Addr = ::GetProcAddress(*It, s.c_str()))
+        return CheckImp(Addr, dllimp);
     }
     if (NumNeeded > NumFirst) {
       // The number of modules was too small to get them all, so call again
@@ -563,8 +585,8 @@ const void* DLSym(const std::string& Name, std::string* Err) {
       if (::EnumProcessModulesEx(::GetCurrentProcess(), &Modules[0],
                                Modules.capacity_in_bytes(), &Bytes, Flags) != 0) {
         for (DWORD i = NumNeeded-1; i > NumFirst; --i) {
-          if (const void* Addr = ::GetProcAddress(Modules[i], Name.c_str()))
-            return Addr;
+          if (void* Addr = ::GetProcAddress(Modules[i], s.c_str()))
+            return CheckImp(Addr, dllimp);
         }
       } else if (Err)
         GetLastErrorAsString(*Err, "EnumProcessModulesEx");