Refactor DynamicLibrary so searching for a symbol will have a defined order and

libraries are properly unloaded when llvm_shutdown is called.

Summary:
This was mostly affecting usage of the JIT, where storing the library handles in
a set made iteration unordered/undefined. This lead to disagreement between the
JIT and native code as to what the address and implementation of particularly on
Windows with stdlib functions:

JIT: putenv_s("TEST", "VALUE") // called msvcrt.dll, putenv_s
JIT: getenv("TEST") -> "VALUE" // called msvcrt.dll, getenv
Native: getenv("TEST") -> NULL // called ucrt.dll, getenv

Also fixed is the issue of DynamicLibrary::getPermanentLibrary(0,0) on Windows
not giving priority to the process' symbols as it did on Unix.

Reviewers: chapuni, v.g.vassilev, lhames

Reviewed By: lhames

Subscribers: danalbert, srhines, mgorny, vsk, llvm-commits

Differential Revision: https://reviews.llvm.org/D30107

llvm-svn: 301153

1 files changed, 131 insertions, 0 deletions

diff --git a/llvm/lib/Support/Unix/DynamicLibrary.inc b/llvm/lib/Support/Unix/DynamicLibrary.inc
new file mode 100644
index 00000000000..a0110e7044e
--- /dev/null
+++ b/llvm/lib/Support/Unix/DynamicLibrary.inc
@@ -0,0 +1,131 @@
+//===- Unix/DynamicLibrary.cpp - Unix DL Implementation ---------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides the UNIX specific implementation of DynamicLibrary.
+//
+//===----------------------------------------------------------------------===//
+
+#if defined(HAVE_DLFCN_H) && defined(HAVE_DLOPEN)
+#include <dlfcn.h>
+
+DynamicLibrary::HandleSet::~HandleSet() {
+  for (void *Handle : Handles)
+    ::dlclose(Handle);
+  if (Process)
+    ::dlclose(Process);
+}
+
+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 (!Filename)
+    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 &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
+
+// 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__) and !defined(__ANDROID__)
+  {
+    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;
+}