1//===-- llvm/Support/DynamicLibrary.h - Portable Dynamic Library -*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file declares the sys::DynamicLibrary class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_SUPPORT_DYNAMICLIBRARY_H
14#define LLVM_SUPPORT_DYNAMICLIBRARY_H
15
16#include <string>
17
18namespace llvm {
19
20class StringRef;
21
22namespace sys {
23
24 /// This class provides a portable interface to dynamic libraries which also
25 /// might be known as shared libraries, shared objects, dynamic shared
26 /// objects, or dynamic link libraries. Regardless of the terminology or the
27 /// operating system interface, this class provides a portable interface that
28 /// allows dynamic libraries to be loaded and searched for externally
29 /// defined symbols. This is typically used to provide "plug-in" support.
30 /// It also allows for symbols to be defined which don't live in any library,
31 /// but rather the main program itself, useful on Windows where the main
32 /// executable cannot be searched.
33 ///
34 /// Note: there is currently no interface for temporarily loading a library,
35 /// or for unloading libraries when the LLVM library is unloaded.
36 class DynamicLibrary {
37 // Placeholder whose address represents an invalid library.
38 // We use this instead of NULL or a pointer-int pair because the OS library
39 // might define 0 or 1 to be "special" handles, such as "search all".
40 static char Invalid;
41
42 // Opaque data used to interface with OS-specific dynamic library handling.
43 void *Data;
44
45 public:
46 explicit DynamicLibrary(void *data = &Invalid) : Data(data) {}
47
48 /// Returns true if the object refers to a valid library.
49 bool isValid() const { return Data != &Invalid; }
50
51 /// Searches through the library for the symbol \p symbolName. If it is
52 /// found, the address of that symbol is returned. If not, NULL is returned.
53 /// Note that NULL will also be returned if the library failed to load.
54 /// Use isValid() to distinguish these cases if it is important.
55 /// Note that this will \e not search symbols explicitly registered by
56 /// AddSymbol().
57 void *getAddressOfSymbol(const char *symbolName);
58
59 /// This function permanently loads the dynamic library at the given path.
60 /// The library will only be unloaded when llvm_shutdown() is called.
61 /// This returns a valid DynamicLibrary instance on success and an invalid
62 /// instance on failure (see isValid()). \p *errMsg will only be modified
63 /// if the library fails to load.
64 ///
65 /// It is safe to call this function multiple times for the same library.
66 /// Open a dynamic library permanently.
67 static DynamicLibrary getPermanentLibrary(const char *filename,
68 std::string *errMsg = nullptr);
69
70 /// Registers an externally loaded library. The library will be unloaded
71 /// when the program terminates.
72 ///
73 /// It is safe to call this function multiple times for the same library,
74 /// though ownership is only taken if there was no error.
75 ///
76 /// \returns An empty \p DynamicLibrary if the library was already loaded.
77 static DynamicLibrary addPermanentLibrary(void *handle,
78 std::string *errMsg = nullptr);
79
80 /// This function permanently loads the dynamic library at the given path.
81 /// Use this instead of getPermanentLibrary() when you won't need to get
82 /// symbols from the library itself.
83 ///
84 /// It is safe to call this function multiple times for the same library.
85 static bool LoadLibraryPermanently(const char *Filename,
86 std::string *ErrMsg = nullptr) {
87 return !getPermanentLibrary(Filename, ErrMsg).isValid();
88 }
89
90 enum SearchOrdering {
91 /// SO_Linker - Search as a call to dlsym(dlopen(NULL)) would when
92 /// DynamicLibrary::getPermanentLibrary(NULL) has been called or
93 /// search the list of explcitly loaded symbols if not.
94 SO_Linker,
95 /// SO_LoadedFirst - Search all loaded libraries, then as SO_Linker would.
96 SO_LoadedFirst,
97 /// SO_LoadedLast - Search as SO_Linker would, then loaded libraries.
98 /// Only useful to search if libraries with RTLD_LOCAL have been added.
99 SO_LoadedLast,
100 /// SO_LoadOrder - Or this in to search libraries in the ordered loaded.
101 /// The default bahaviour is to search loaded libraries in reverse.
102 SO_LoadOrder = 4
103 };
104 static SearchOrdering SearchOrder; // = SO_Linker
105
106 /// This function will search through all previously loaded dynamic
107 /// libraries for the symbol \p symbolName. If it is found, the address of
108 /// that symbol is returned. If not, null is returned. Note that this will
109 /// search permanently loaded libraries (getPermanentLibrary()) as well
110 /// as explicitly registered symbols (AddSymbol()).
111 /// @throws std::string on error.
112 /// Search through libraries for address of a symbol
113 static void *SearchForAddressOfSymbol(const char *symbolName);
114
115 /// Convenience function for C++ophiles.
116 static void *SearchForAddressOfSymbol(const std::string &symbolName) {
117 return SearchForAddressOfSymbol(symbolName.c_str());
118 }
119
120 /// This functions permanently adds the symbol \p symbolName with the
121 /// value \p symbolValue. These symbols are searched before any
122 /// libraries.
123 /// Add searchable symbol/value pair.
124 static void AddSymbol(StringRef symbolName, void *symbolValue);
125
126 class HandleSet;
127 };
128
129} // End sys namespace
130} // End llvm namespace
131
132#endif
133