support/lib/System/DynamicLibrary.cpp

//===-- DynamicLibrary.cpp - Runtime link/load libraries --------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Reid Spencer and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This header file implements the operating system DynamicLibrary concept.
//
//===----------------------------------------------------------------------===//

#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
// the LGPL.  This is because the exception applies only when libtool is
// used, and obviously libtool is not used with Visual Studio.  An entirely
// separate implementation is provided in win32/DynamicLibrary.cpp.

#ifdef LLVM_ON_WIN32

#include "Win32/DynamicLibrary.inc"

#else

#include "ltdl.h"
#include <cassert>
using namespace llvm;
using namespace llvm::sys;

//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only TRULY operating system
//===          independent code.
//===----------------------------------------------------------------------===//

static inline void check_ltdl_initialization() {
  static bool did_initialize_ltdl = false;
  if (!did_initialize_ltdl) {
    int Err = lt_dlinit();
    Err = Err; // Silence warning.
    assert(0 == Err && "Can't init the ltdl library");
    did_initialize_ltdl = true;
  }
}

static std::vector<lt_dlhandle> OpenedHandles;

DynamicLibrary::DynamicLibrary() : handle(0) {
  check_ltdl_initialization();

  lt_dlhandle a_handle = lt_dlopen(0);

  assert(a_handle && "Can't open program as dynamic library");

  handle = a_handle;
  OpenedHandles.push_back(a_handle);
}

/*
DynamicLibrary::DynamicLibrary(const char*filename) : handle(0) {
  check_ltdl_initialization();

  lt_dlhandle a_handle = lt_dlopen(filename);

  if (a_handle == 0)
    a_handle = lt_dlopenext(filename);

  if (a_handle == 0)
    throw std::string("Can't open :") + filename + ": " + lt_dlerror();

  handle = a_handle;
  OpenedHandles.push_back(a_handle);
}
*/

DynamicLibrary::~DynamicLibrary() {
  lt_dlhandle a_handle = (lt_dlhandle) handle;
  if (a_handle) {
    lt_dlclose(a_handle);

    for (std::vector<lt_dlhandle>::iterator I = OpenedHandles.begin(),
         E = OpenedHandles.end(); I != E; ++I) {
      if (*I == a_handle) {
        // Note: don't use the swap/pop_back trick here. Order is important.
        OpenedHandles.erase(I);
        return;
      }
    }
  }
}

bool DynamicLibrary::LoadLibraryPermanently(const char *Filename,
                                            std::string *ErrMsg) {
  check_ltdl_initialization();
  lt_dlhandle a_handle = lt_dlopen(Filename);

  if (a_handle == 0)
    a_handle = lt_dlopenext(Filename);

  if (a_handle == 0) {
    if (ErrMsg)
      *ErrMsg = std::string("Can't open :") +
          (Filename ? Filename : "<current process>") + ": " + lt_dlerror();
    return true;
  }

  lt_dlmakeresident(a_handle);

  OpenedHandles.push_back(a_handle);
  return false;
}

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);
    if (ptr)
      return ptr;
  }

#define EXPLICIT_SYMBOL(SYM) \
   extern void *SYM; if (!strcmp(symbolName, #SYM)) return &SYM

  // If this is darwin, it has some funky issues, try to solve them here.  Some
  // important symbols are marked 'private external' which doesn't allow
  // SearchForAddressOfSymbol to find them.  As such, we special case them here,
  // there is only a small handful of them.

#ifdef __APPLE__
  {
    EXPLICIT_SYMBOL(__ashldi3);
    EXPLICIT_SYMBOL(__ashrdi3);
    EXPLICIT_SYMBOL(__cmpdi2);
    EXPLICIT_SYMBOL(__divdi3);
    EXPLICIT_SYMBOL(__eprintf);
    EXPLICIT_SYMBOL(__fixdfdi);
    EXPLICIT_SYMBOL(__fixsfdi);
    EXPLICIT_SYMBOL(__fixunsdfdi);
    EXPLICIT_SYMBOL(__fixunssfdi);
    EXPLICIT_SYMBOL(__floatdidf);
    EXPLICIT_SYMBOL(__floatdisf);
    EXPLICIT_SYMBOL(__lshrdi3);
    EXPLICIT_SYMBOL(__moddi3);
    EXPLICIT_SYMBOL(__udivdi3);
    EXPLICIT_SYMBOL(__umoddi3);
  }
#endif

#ifdef __CYGWIN__
  {
    EXPLICIT_SYMBOL(_alloca);
  }
#endif

#undef EXPLICIT_SYMBOL

// This macro returns the address of a well-known, explicit symbol
#define EXPLICIT_SYMBOL(SYM) \
   if (!strcmp(symbolName, #SYM)) return &SYM

// On linux we have a weird situation. The stderr/out/in symbols are both
// macros and global variables because of standards requirements. So, we 
// boldly use the EXPLICIT_SYMBOL macro without checking for a #define first.
#if defined(__linux__)
  {
    EXPLICIT_SYMBOL(stderr);
    EXPLICIT_SYMBOL(stdout);
    EXPLICIT_SYMBOL(stdin);
  }
#else
  // For everything else, we want to check to make sure the symbol isn't defined
  // as a macro before using EXPLICIT_SYMBOL.
  {
#ifndef stdin
    EXPLICIT_SYMBOL(stdin);
#endif
#ifndef stdout
    EXPLICIT_SYMBOL(stdout);
#endif
#ifndef stderr
    EXPLICIT_SYMBOL(stderr);
#endif
  }
#endif
#undef EXPLICIT_SYMBOL

  return 0;
}

void *DynamicLibrary::GetAddressOfSymbol(const char *symbolName) {
  assert(handle != 0 && "Invalid DynamicLibrary handle");
  return lt_dlsym((lt_dlhandle) handle, symbolName);
}

#endif // LLVM_ON_WIN32

DEFINING_FILE_FOR(SystemDynamicLibrary)