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 | |
19 | namespace llvm { |
20 | |
21 | class StringRef; |
22 | |
23 | namespace 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 | |