From a9b7d60d67b054541cb8507d697eb94beee32f18 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 7 Jul 2009 18:17:07 +0000
Subject: Eliminate the static constructors and locks from DynamicLibrary.cpp.
 This fixes PR4512 and eliminating static ctors is always good.  Losing thread
 safety is unfortunate, but the code is just incredibly poorly designed.

If someone is interested, the "right" solution is to split
DynamicLibrary.cpp into two separate pieces: a stateless piece in
libsystem, and a simple support file in libsupport that has the
"state" (e.g.  AddSymbol) in managed static objects.

Doing this would both fix memory leaks we already have, as well as make
the code thread safe again.  it would also make sense to move all the
unix specific code in System/DynamicLibrary.cpp into
System/Unix/DynamicLibrary.inc.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74927 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/System/DynamicLibrary.cpp | 53 ++++++++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

(limited to 'lib/System/DynamicLibrary.cpp')

diff --git a/lib/System/DynamicLibrary.cpp b/lib/System/DynamicLibrary.cpp
index b88d03f494..669422c842 100644
--- a/lib/System/DynamicLibrary.cpp
+++ b/lib/System/DynamicLibrary.cpp
@@ -9,11 +9,13 @@
 //
 //  This header file implements the operating system DynamicLibrary concept.
 //
+// FIXME: This file leaks the ExplicitSymbols and OpenedHandles vector, and is
+// not thread safe!
+//
 //===----------------------------------------------------------------------===//
 
 #include "llvm/System/DynamicLibrary.h"
 #include "llvm/Support/ManagedStatic.h"
-#include "llvm/System/RWMutex.h"
 #include "llvm/Config/config.h"
 #include <cstdio>
 #include <cstring>
@@ -21,13 +23,13 @@
 #include <vector>
 
 // Collection of symbol name/value pairs to be searched prior to any libraries.
-static std::map<std::string, void*> symbols;
-static llvm::sys::SmartRWMutex<true> SymbolsLock;
+static std::map<std::string, void*> *ExplicitSymbols = 0;
 
 void llvm::sys::DynamicLibrary::AddSymbol(const char* symbolName,
                                           void *symbolValue) {
-  llvm::sys::SmartScopedWriter<true> Writer(&SymbolsLock);
-  symbols[symbolName] = symbolValue;
+  if (ExplicitSymbols == 0)
+    ExplicitSymbols = new std::map<std::string, void*>();
+  (*ExplicitSymbols)[symbolName] = symbolValue;
 }
 
 #ifdef LLVM_ON_WIN32
@@ -37,7 +39,6 @@ void llvm::sys::DynamicLibrary::AddSymbol(const char* symbolName,
 #else
 
 #include <dlfcn.h>
-#include <cassert>
 using namespace llvm;
 using namespace llvm::sys;
 
@@ -46,44 +47,44 @@ using namespace llvm::sys;
 //===          independent code.
 //===----------------------------------------------------------------------===//
 
-static std::vector<void *> OpenedHandles;
+static std::vector<void *> *OpenedHandles = 0;
 
 
 bool DynamicLibrary::LoadLibraryPermanently(const char *Filename,
                                             std::string *ErrMsg) {
-  SmartScopedWriter<true> Writer(&SymbolsLock);                                              
   void *H = dlopen(Filename, RTLD_LAZY|RTLD_GLOBAL);
   if (H == 0) {
-    if (ErrMsg)
-      *ErrMsg = dlerror();
+    if (ErrMsg) *ErrMsg = dlerror();
     return true;
   }
-  OpenedHandles.push_back(H);
+  if (OpenedHandles == 0)
+    OpenedHandles = new std::vector<void *>();
+  OpenedHandles->push_back(H);
   return false;
 }
 
 void* DynamicLibrary::SearchForAddressOfSymbol(const char* symbolName) {
   // First check symbols added via AddSymbol().
-  SymbolsLock.reader_acquire();
-  std::map<std::string, void *>::iterator I = symbols.find(symbolName);
-  std::map<std::string, void *>::iterator E = symbols.end();
-  SymbolsLock.reader_release();
+  if (ExplicitSymbols) {
+    std::map<std::string, void *>::iterator I =
+      ExplicitSymbols->find(symbolName);
+    std::map<std::string, void *>::iterator E = ExplicitSymbols->end();
   
-  if (I != E)
-    return I->second;
+    if (I != E)
+      return I->second;
+  }
 
-  SymbolsLock.writer_acquire();
   // Now search the libraries.
-  for (std::vector<void *>::iterator I = OpenedHandles.begin(),
-       E = OpenedHandles.end(); I != E; ++I) {
-    //lt_ptr ptr = lt_dlsym(*I, symbolName);
-    void *ptr = dlsym(*I, symbolName);
-    if (ptr) {
-      SymbolsLock.writer_release();
-      return ptr;
+  if (OpenedHandles) {
+    for (std::vector<void *>::iterator I = OpenedHandles->begin(),
+         E = OpenedHandles->end(); I != E; ++I) {
+      //lt_ptr ptr = lt_dlsym(*I, symbolName);
+      void *ptr = dlsym(*I, symbolName);
+      if (ptr) {
+        return ptr;
+      }
     }
   }
-  SymbolsLock.writer_release();
 
 #define EXPLICIT_SYMBOL(SYM) \
    extern void *SYM; if (!strcmp(symbolName, #SYM)) return &SYM
-- 
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