Use DynamicLibrary instances as a way to get symbols from a specific library. Preparation for upcoming (preliminary) support for plugins for the static analyzer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137791 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/DynamicLibrary.h

@@ -28,36 +28,57 @@ namespace sys {
   /// 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.
+  ///
+  /// Note: there is currently no interface for temporarily loading a library,
+  /// or for unloading libraries when the LLVM library is unloaded.
   class DynamicLibrary {
-    DynamicLibrary(); // DO NOT IMPLEMENT
+    // Opaque data used to interface with OS-specific dynamic library handling.
+    void *Data;
+
+    explicit DynamicLibrary(void *data = 0) : Data(data) {}
   public:
-    /// This function allows a library to be loaded without instantiating a
-    /// DynamicLibrary object. Consequently, it is marked as being permanent
-    /// and will only be unloaded when the program terminates.  This returns
-    /// false on success or returns true and fills in *ErrMsg on failure.
-    /// @brief Open a dynamic library permanently.
+    /// Returns true if the object refers to a valid library.
+    bool isValid() { return Data != 0; }
+
+    /// Searches through the library for the symbol \p symbolName. If it is
+    /// found, the address of that symbol is returned. If not, NULL is returned.
+    /// Note that NULL will also be returned if the library failed to load.
+    /// Use isValid() to distinguish these cases if it is important.
+    /// Note that this will \e not search symbols explicitly registered by
+    /// AddSymbol().
+    void *getAddressOfSymbol(const char *symbolName);
+
+    /// This function permanently loads the dynamic library at the given path.
+    /// The library will only be unloaded when the program terminates.
+    /// This returns a valid DynamicLibrary instance on success and an invalid
+    /// instance on failure (see isValid()). \p *errMsg will only be modified
+    /// if the library fails to load.
     ///
-    /// NOTE: This function is not thread safe.
+    /// It is safe to call this function multiple times for the same library.
+    /// @brief Open a dynamic library permanently.
+    static DynamicLibrary getPermanentLibrary(const char *filename,
+                                              std::string *errMsg = 0);
+
+    /// 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.
     ///
-    static bool LoadLibraryPermanently(const char *filename,
-                                       std::string *ErrMsg = 0);
+    /// It is safe to call this function multiple times for the same library.
+    static bool LoadLibraryPermanently(const char *Filename,
+                                       std::string *ErrMsg = 0) {
+      return !getPermanentLibrary(Filename, ErrMsg).isValid();
+    }
 
     /// This function will search through all previously loaded dynamic
-    /// libraries for the symbol \p symbolName. If it is found, the addressof
+    /// libraries for the symbol \p symbolName. If it is found, the address of
     /// that symbol is returned. If not, null is returned. Note that this will
-    /// search permanently loaded libraries (LoadLibraryPermanently) as well
-    /// as ephemerally loaded libraries (constructors).
+    /// search permanently loaded libraries (getPermanentLibrary()) as well
+    /// as explicitly registered symbols (AddSymbol()).
     /// @throws std::string on error.
     /// @brief Search through libraries for address of a symbol
-    ///
-    /// NOTE: This function is not thread safe.
-    ///
     static void *SearchForAddressOfSymbol(const char *symbolName);
 
     /// @brief Convenience function for C++ophiles.
-    ///
-    /// NOTE: This function is not thread safe.
-    ///
     static void *SearchForAddressOfSymbol(const std::string &symbolName) {
       return SearchForAddressOfSymbol(symbolName.c_str());
     }
@@ -66,18 +87,7 @@ namespace sys {
     /// value \p symbolValue.  These symbols are searched before any
     /// libraries.
     /// @brief Add searchable symbol/value pair.
-    ///
-    /// NOTE: This function is not thread safe.
-    ///
-    static void AddSymbol(const char *symbolName, void *symbolValue);
-
-    /// @brief Convenience function for C++ophiles.
-    ///
-    /// NOTE: This function is not thread safe.
-    ///
-    static void AddSymbol(const std::string &symbolName, void *symbolValue) {
-      AddSymbol(symbolName.c_str(), symbolValue);
-    }
+    static void AddSymbol(StringRef symbolName, void *symbolValue);
   };
 
 } // End sys namespace

lib/Support/DynamicLibrary.cpp

@@ -9,28 +9,26 @@
 //
 //  This header file implements the operating system DynamicLibrary concept.
 //
-// FIXME: This file leaks the ExplicitSymbols and OpenedHandles vector, and is
-// not thread safe!
+// FIXME: This file leaks ExplicitSymbols and OpenedHandles!
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/Support/DynamicLibrary.h"
 #include "llvm/Support/Mutex.h"
 #include "llvm/Config/config.h"
 #include <cstdio>
 #include <cstring>
-#include <map>
-#include <vector>
 
 // Collection of symbol name/value pairs to be searched prior to any libraries.
-static std::map<std::string, void*> *ExplicitSymbols = 0;
+static llvm::StringMap<void *> *ExplicitSymbols = 0;
 
 namespace {
 
 struct ExplicitSymbolsDeleter {
   ~ExplicitSymbolsDeleter() {
-    if (ExplicitSymbols)
-      delete ExplicitSymbols;
+    delete ExplicitSymbols;
   }
 };
 
@@ -38,10 +36,17 @@ struct ExplicitSymbolsDeleter {
 
 static ExplicitSymbolsDeleter Dummy;
 
-void llvm::sys::DynamicLibrary::AddSymbol(const char* symbolName,
+
+static llvm::sys::SmartMutex<true>& getMutex() {
+  static llvm::sys::SmartMutex<true> HandlesMutex;
+  return HandlesMutex;
+}
+
+void llvm::sys::DynamicLibrary::AddSymbol(StringRef symbolName,
                                           void *symbolValue) {
+  SmartScopedLock<true> lock(getMutex());
   if (ExplicitSymbols == 0)
-    ExplicitSymbols = new std::map<std::string, void*>();
+    ExplicitSymbols = new llvm::StringMap<void*>();
   (*ExplicitSymbols)[symbolName] = symbolValue;
 }
 
@@ -61,66 +66,77 @@ using namespace llvm::sys;
 //===          independent code.
 //===----------------------------------------------------------------------===//
 
-static std::vector<void *> *OpenedHandles = 0;
-
-
-static SmartMutex<true>& getMutex() {
-  static SmartMutex<true> HandlesMutex;
-  return HandlesMutex;
-}
-
+static DenseSet<void *> *OpenedHandles = 0;
 
-bool DynamicLibrary::LoadLibraryPermanently(const char *Filename,
-                                            std::string *ErrMsg) {
-  void *H = dlopen(Filename, RTLD_LAZY|RTLD_GLOBAL);
-  if (H == 0) {
-    if (ErrMsg) *ErrMsg = dlerror();
-    return true;
+DynamicLibrary DynamicLibrary::getPermanentLibrary(const char *filename,
+                                                   std::string *errMsg) {
+  void *handle = dlopen(filename, RTLD_LAZY|RTLD_GLOBAL);
+  if (handle == 0) {
+    if (errMsg) *errMsg = dlerror();
+    return DynamicLibrary();
   }
+
 #ifdef __CYGWIN__
   // Cygwin searches symbols only in the main
   // with the handle of dlopen(NULL, RTLD_GLOBAL).
-  if (Filename == NULL)
-    H = RTLD_DEFAULT;
+  if (filename == NULL)
+    handle = RTLD_DEFAULT;
 #endif
-  SmartScopedLock<true> Lock(getMutex());
+
+  SmartScopedLock<true> lock(getMutex());
   if (OpenedHandles == 0)
-    OpenedHandles = new std::vector<void *>();
-  OpenedHandles->push_back(H);
-  return false;
+    OpenedHandles = new DenseSet<void *>();
+
+  // If we've already loaded this library, dlclose() the handle in order to
+  // keep the internal refcount at +1.
+  if (!OpenedHandles->insert(handle).second)
+    dlclose(handle);
+
+  return DynamicLibrary(handle);
+}
+
+void *DynamicLibrary::getAddressOfSymbol(const char *symbolName) {
+  if (!isValid())
+    return NULL;
+  return dlsym(Data, symbolName);
 }
+
 #else
 
 using namespace llvm;
 using namespace llvm::sys;
 
-bool DynamicLibrary::LoadLibraryPermanently(const char *Filename,
-                                            std::string *ErrMsg) {
-  if (ErrMsg) *ErrMsg = "dlopen() not supported on this platform";
-  return true;
+DynamicLibrary DynamicLibrary::getPermanentLibrary(const char *filename,
+                                                   std::string *errMsg) {
+  if (errMsg) *errMsg = "dlopen() not supported on this platform";
+  return DynamicLibrary();
 }
+
+void *DynamicLibrary::getAddressOfSymbol(const char *symbolName) {
+  return NULL;
+}
+
 #endif
 
 namespace llvm {
 void *SearchForAddressOfSpecialSymbol(const char* symbolName);
 }
 
-void* DynamicLibrary::SearchForAddressOfSymbol(const char* symbolName) {
+void* DynamicLibrary::SearchForAddressOfSymbol(const char *symbolName) {
+  SmartScopedLock<true> Lock(getMutex());
+
   // First check symbols added via AddSymbol().
   if (ExplicitSymbols) {
-    std::map<std::string, void *>::iterator I =
-      ExplicitSymbols->find(symbolName);
-    std::map<std::string, void *>::iterator E = ExplicitSymbols->end();
+    StringMap<void *>::iterator i = ExplicitSymbols->find(symbolName);
 
-    if (I != E)
-      return I->second;
+    if (i != ExplicitSymbols->end())
+      return i->second;
   }
 
 #if HAVE_DLFCN_H
   // Now search the libraries.
-  SmartScopedLock<true> Lock(getMutex());
   if (OpenedHandles) {
-    for (std::vector<void *>::iterator I = OpenedHandles->begin(),
+    for (DenseSet<void *>::iterator I = OpenedHandles->begin(),
          E = OpenedHandles->end(); I != E; ++I) {
       //lt_ptr ptr = lt_dlsym(*I, symbolName);
       void *ptr = dlsym(*I, symbolName);

lib/Support/Windows/DynamicLibrary.inc

@@ -39,7 +39,7 @@ using namespace sys;
 //===          and must not be UNIX code.
 //===----------------------------------------------------------------------===//
 
-static std::vector<HMODULE> OpenedHandles;
+static DenseSet<HMODULE> *OpenedHandles;
 
 extern "C" {
 
@@ -63,30 +63,43 @@ extern "C" {
 #endif
         stricmp(ModuleName, "msvcrt20") != 0 &&
         stricmp(ModuleName, "msvcrt40") != 0) {
-      OpenedHandles.push_back((HMODULE)ModuleBase);
+      OpenedHandles->push_back((HMODULE)ModuleBase);
     }
     return TRUE;
   }
 }
 
-bool DynamicLibrary::LoadLibraryPermanently(const char *filename,
-                                            std::string *ErrMsg) {
-  if (filename) {
-    HMODULE a_handle = LoadLibrary(filename);
+DynamicLibrary DynamicLibrary::getPermanentLibrary(const char *filename,
+                                                   std::string *errMsg) {
+  if (!filename) {
+    // When no file is specified, enumerate all DLLs and EXEs in the process.
+    SmartScopedLock<true> lock(getMutex());
+    if (OpenedHandles == 0)
+      OpenedHandles = new DenseSet<HMODULE>();
 
-    if (a_handle == 0)
-      return MakeErrMsg(ErrMsg, std::string(filename) + ": Can't open : ");
-
-    OpenedHandles.push_back(a_handle);
-  } else {
-    // When no file is specified, enumerate all DLLs and EXEs in the
-    // process.
     EnumerateLoadedModules(GetCurrentProcess(), ELM_Callback, 0);
+    // Dummy library that represents "search all handles".
+    // This is mostly to ensure that the return value still shows up as "valid".
+    return DynamicLibrary(&OpenedHandles);
+  }
+  
+  HMODULE a_handle = LoadLibrary(filename);
+
+  if (a_handle == 0) {
+    MakeErrMsg(ErrMsg, std::string(filename) + ": Can't open : ");
+    return DynamicLibrary();
   }
 
-  // Because we don't remember the handle, we will never free it; hence,
-  // it is loaded permanently.
-  return false;
+  SmartScopedLock<true> lock(getMutex());
+  if (OpenedHandles == 0)
+    OpenedHandles = new DenseSet<HMODULE>();
+
+  // If we've already loaded this library, FreeLibrary() the handle in order to
+  // keep the internal refcount at +1.
+  if (!OpenedHandles->insert(a_handle).second)
+    FreeLibrary(a_handle);
+
+  return DynamicLibrary(a_handle);
 }
 
 // Stack probing routines are in the support library (e.g. libgcc), but we don't
@@ -101,21 +114,24 @@ bool DynamicLibrary::LoadLibraryPermanently(const char *filename,
 #undef EXPLICIT_SYMBOL2
 
 void* DynamicLibrary::SearchForAddressOfSymbol(const char* symbolName) {
+  SmartScopedLock<true> Lock(getMutex());
+
   // First check symbols added via AddSymbol().
   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;
+    StringMap<void *>::iterator i = ExplicitSymbols->find(symbolName);
+
+    if (i != ExplicitSymbols->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);
-    if (ptr) {
-      return (void *)(intptr_t)ptr;
+  if (OpenedHandles) {
+    for (DenseSet<HMODULE>::iterator I = OpenedHandles->begin(),
+         E = OpenedHandles->end(); I != E; ++I) {
+      FARPROC ptr = GetProcAddress((HMODULE)*I, symbolName);
+      if (ptr) {
+        return (void *)(intptr_t)ptr;
+      }
     }
   }
 
@@ -134,4 +150,14 @@ void* DynamicLibrary::SearchForAddressOfSymbol(const char* symbolName) {
   return 0;
 }
 
+
+void *DynamicLibrary::getAddressOfSymbol(const char *symbolName) {
+  if (!isValid())
+    return NULL;
+  if (Data == &OpenedHandles)
+    return SearchForAddressOfSymbol(symbolName);
+  return (void *)(intptr_t)GetProcAddress((HMODULE)Data, symbolName);
+}
+
+
 }