1//===-- llvm/Support/DynamicLibrary.h - Portable Dynamic Library -*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file declares the sys::DynamicLibrary class.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_SUPPORT_DYNAMICLIBRARY_H
15#define LLVM_SUPPORT_DYNAMICLIBRARY_H
16
17#include <string>
18
19namespace llvm {
20
21class StringRef;
22
23namespace sys {
24
25 /// This class provides a portable interface to dynamic libraries which also
26 /// might be known as shared libraries, shared objects, dynamic shared
27 /// objects, or dynamic link libraries. Regardless of the terminology or the
28 /// operating system interface, this class provides a portable interface that
29 /// allows dynamic libraries to be loaded and searched for externally
30 /// defined symbols. This is typically used to provide "plug-in" support.
31 /// It also allows for symbols to be defined which don't live in any library,
32 /// but rather the main program itself, useful on Windows where the main
33 /// executable cannot be searched.
34 ///
35 /// Note: there is currently no interface for temporarily loading a library,
36 /// or for unloading libraries when the LLVM library is unloaded.
37 class DynamicLibrary {
38 // Placeholder whose address represents an invalid library.
39 // We use this instead of NULL or a pointer-int pair because the OS library
40 // might define 0 or 1 to be "special" handles, such as "search all".
41 static char Invalid;
42
43 // Opaque data used to interface with OS-specific dynamic library handling.
44 void *Data;
45
46 public:
47 explicit DynamicLibrary(void *data = &Invalid) : Data(data) {}
48
49 /// Returns true if the object refers to a valid library.
50 bool isValid() const { return Data != &Invalid; }
51
52 /// Searches through the library for the symbol \p symbolName. If it is
53 /// found, the address of that symbol is returned. If not, NULL is returned.
54 /// Note that NULL will also be returned if the library failed to load.
55 /// Use isValid() to distinguish these cases if it is important.
56 /// Note that this will \e not search symbols explicitly registered by
57 /// AddSymbol().
58 void *getAddressOfSymbol(const char *symbolName);
59
60 /// This function permanently loads the dynamic library at the given path.
61 /// The library will only be unloaded when llvm_shutdown() is called.
62 /// This returns a valid DynamicLibrary instance on success and an invalid
63 /// instance on failure (see isValid()). \p *errMsg will only be modified
64 /// if the library fails to load.
65 ///
66 /// It is safe to call this function multiple times for the same library.
67 /// Open a dynamic library permanently.
68 static DynamicLibrary getPermanentLibrary(const char *filename,
69 std::string *errMsg = nullptr);
70
71 /// Registers an externally loaded library. The library will be unloaded
72 /// when the program terminates.
73 ///
74 /// It is safe to call this function multiple times for the same library,
75 /// though ownership is only taken if there was no error.
76 ///
77 /// \returns An empty \p DynamicLibrary if the library was already loaded.
78 static DynamicLibrary addPermanentLibrary(void *handle,
79 std::string *errMsg = nullptr);
80
81 /// This function permanently loads the dynamic library at the given path.
82 /// Use this instead of getPermanentLibrary() when you won't need to get
83 /// symbols from the library itself.
84 ///
85 /// It is safe to call this function multiple times for the same library.
86 static bool LoadLibraryPermanently(const char *Filename,
87 std::string *ErrMsg = nullptr) {
88 return !getPermanentLibrary(Filename, ErrMsg).isValid();
89 }
90
91 enum SearchOrdering {
92 /// SO_Linker - Search as a call to dlsym(dlopen(NULL)) would when
93 /// DynamicLibrary::getPermanentLibrary(NULL) has been called or
94 /// search the list of explcitly loaded symbols if not.
95 SO_Linker,
96 /// SO_LoadedFirst - Search all loaded libraries, then as SO_Linker would.
97 SO_LoadedFirst,
98 /// SO_LoadedLast - Search as SO_Linker would, then loaded libraries.
99 /// Only useful to search if libraries with RTLD_LOCAL have been added.
100 SO_LoadedLast,
101 /// SO_LoadOrder - Or this in to search libraries in the ordered loaded.
102 /// The default bahaviour is to search loaded libraries in reverse.
103 SO_LoadOrder = 4
104 };
105 static SearchOrdering SearchOrder; // = SO_Linker
106
107 /// This function will search through all previously loaded dynamic
108 /// libraries for the symbol \p symbolName. If it is found, the address of
109 /// that symbol is returned. If not, null is returned. Note that this will
110 /// search permanently loaded libraries (getPermanentLibrary()) as well
111 /// as explicitly registered symbols (AddSymbol()).
112 /// @throws std::string on error.
113 /// Search through libraries for address of a symbol
114 static void *SearchForAddressOfSymbol(const char *symbolName);
115
116 /// Convenience function for C++ophiles.
117 static void *SearchForAddressOfSymbol(const std::string &symbolName) {
118 return SearchForAddressOfSymbol(symbolName.c_str());
119 }
120
121 /// This functions permanently adds the symbol \p symbolName with the
122 /// value \p symbolValue. These symbols are searched before any
123 /// libraries.
124 /// Add searchable symbol/value pair.
125 static void AddSymbol(StringRef symbolName, void *symbolValue);
126
127 class HandleSet;
128 };
129
130} // End sys namespace
131} // End llvm namespace
132
133#endif
134