DynamicLibrary.inc

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//===- Unix/DynamicLibrary.cpp - Unix DL Implementation ---------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file provides the UNIX specific implementation of DynamicLibrary.
//
//===----------------------------------------------------------------------===//
 
#if defined(HAVE_DLOPEN)
#include <dlfcn.h>
 
DynamicLibrary::HandleSet::~HandleSet() {
  // Close the libraries in reverse order.
  for (void *Handle : llvm::reverse(Handles))
    ::dlclose(Handle);
  if (Process)
    ::dlclose(Process);
 
  // llvm_shutdown called, Return to default
  DynamicLibrary::SearchOrder = DynamicLibrary::SO_Linker;
}
 
void *DynamicLibrary::HandleSet::DLOpen(const char *File, std::string *Err) {
  void *Handle = ::dlopen(File, RTLD_LAZY | RTLD_GLOBAL);
  if (!Handle) {
    if (Err)
      *Err = ::dlerror();
    return &DynamicLibrary::Invalid;
  }
 
#ifdef __CYGWIN__
  // Cygwin searches symbols only in the main
  // with the handle of dlopen(NULL, RTLD_GLOBAL).
  if (!File)
    Handle = RTLD_DEFAULT;
#endif
 
  return Handle;
}
 
void DynamicLibrary::HandleSet::DLClose(void *Handle) { ::dlclose(Handle); }
 
void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
  return ::dlsym(Handle, Symbol);
}
 
#else // !HAVE_DLOPEN
 
DynamicLibrary::HandleSet::~HandleSet() {}
 
void *DynamicLibrary::HandleSet::DLOpen(const char *File, std::string *Err) {
  if (Err)
    *Err = "dlopen() not supported on this platform";
  return &Invalid;
}
 
void DynamicLibrary::HandleSet::DLClose(void *Handle) {}
 
void *DynamicLibrary::HandleSet::DLSym(void *Handle, const char *Symbol) {
  return nullptr;
}
 
#endif
 
// Must declare the symbols in the global namespace.
static void *DoSearch(const char *SymbolName) {
#define EXPLICIT_SYMBOL(SYM)                                                   \
  extern void *SYM;                                                            \
  if (!strcmp(SymbolName, #SYM))                                               \
  return (void *)&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__
  {
    // __eprintf is sometimes used for assert() handling on x86.
    //
    // FIXME: Currently disabled when using Clang, as we don't always have our
    // runtime support libraries available.
#ifndef __clang__
#ifdef __i386__
    EXPLICIT_SYMBOL(__eprintf);
#endif
#endif
  }
#endif
 
#ifdef __CYGWIN__
  {
    EXPLICIT_SYMBOL(_alloca);
    EXPLICIT_SYMBOL(__main);
  }
#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
 
// Under glibc 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(__GLIBC__)
  {
    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 nullptr;
}