lib/Linker/LinkItems.cpp

   1 //===- lib/Linker/LinkItems.cpp - Link LLVM objects and libraries ---------===//
   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 contains routines to handle linking together LLVM bitcode files,
  11 // and to handle annoying things like static libraries.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Linker.h"
  16 #include "llvm/Module.h"
  17 #include "llvm/Bitcode/ReaderWriter.h"
  18 #include "llvm/Support/Path.h"
  19 #include "llvm/Support/ErrorHandling.h"
  20 #include "llvm/Support/MemoryBuffer.h"
  21 #include "llvm/Support/system_error.h"
  22 using namespace llvm;
  23
  24 // LinkItems - This function is the main entry point into linking. It takes a
  25 // list of LinkItem which indicates the order the files should be linked and
  26 // how each file should be treated (plain file or with library search). The
  27 // function only links bitcode and produces a result list of items that are
  28 // native objects.
  29 bool
  30 Linker::LinkInItems(const ItemList& Items, ItemList& NativeItems) {
  31   // Clear the NativeItems just in case
  32   NativeItems.clear();
  33
  34   // For each linkage item ...
  35   for (ItemList::const_iterator I = Items.begin(), E = Items.end();
  36        I != E; ++I) {
  37     if (I->second) {
  38       // Link in the library suggested.
  39       bool is_native = false;
  40       if (LinkInLibrary(I->first, is_native))
  41         return true;
  42       if (is_native)
  43         NativeItems.push_back(*I);
  44     } else {
  45       // Link in the file suggested
  46       bool is_native = false;
  47       if (LinkInFile(sys::Path(I->first), is_native))
  48         return true;
  49       if (is_native)
  50         NativeItems.push_back(*I);
  51     }
  52   }
  53
  54   // At this point we have processed all the link items provided to us. Since
  55   // we have an aggregated module at this point, the dependent libraries in
  56   // that module should also be aggregated with duplicates eliminated. This is
  57   // now the time to process the dependent libraries to resolve any remaining
  58   // symbols.
  59   bool is_native;
  60   for (Module::lib_iterator I = Composite->lib_begin(),
  61          E = Composite->lib_end(); I != E; ++I) {
  62     if(LinkInLibrary(*I, is_native))
  63       return true;
  64     if (is_native)
  65       NativeItems.push_back(std::make_pair(*I, true));
  66   }
  67
  68   return false;
  69 }
  70
  71
  72 /// LinkInLibrary - links one library into the HeadModule.
  73 ///
  74 bool Linker::LinkInLibrary(StringRef Lib, bool& is_native) {
  75   is_native = false;
  76   // Determine where this library lives.
  77   sys::Path Pathname = FindLib(Lib);
  78   if (Pathname.isEmpty())
  79     return error("Cannot find library '" + Lib.str() + "'");
  80
  81   // If its an archive, try to link it in
  82   std::string Magic;
  83   Pathname.getMagicNumber(Magic, 64);
  84   switch (sys::IdentifyFileType(Magic.c_str(), 64)) {
  85     default: llvm_unreachable("Bad file type identification");
  86     case sys::Unknown_FileType:
  87       return warning("Supposed library '" + Lib.str() + "' isn't a library.");
  88
  89     case sys::Bitcode_FileType:
  90       // LLVM ".so" file.
  91       if (LinkInFile(Pathname, is_native))
  92         return true;
  93       break;
  94
  95     case sys::Archive_FileType:
  96       if (LinkInArchive(Pathname, is_native))
  97         return error("Cannot link archive '" + Pathname.str() + "'");
  98       break;
  99
 100     case sys::ELF_Relocatable_FileType:
 101     case sys::ELF_SharedObject_FileType:
 102     case sys::Mach_O_Object_FileType:
 103     case sys::Mach_O_FixedVirtualMemorySharedLib_FileType:
 104     case sys::Mach_O_DynamicallyLinkedSharedLib_FileType:
 105     case sys::Mach_O_DynamicallyLinkedSharedLibStub_FileType:
 106     case sys::COFF_FileType:
 107       is_native = true;
 108       break;
 109   }
 110   return false;
 111 }
 112
 113 /// LinkLibraries - takes the specified library files and links them into the
 114 /// main bitcode object file.
 115 ///
 116 /// Inputs:
 117 ///  Libraries  - The list of libraries to link into the module.
 118 ///
 119 /// Return value:
 120 ///  FALSE - No error.
 121 ///  TRUE  - Error.
 122 ///
 123 bool Linker::LinkInLibraries(const std::vector<std::string> &Libraries) {
 124
 125   // Process the set of libraries we've been provided.
 126   bool is_native = false;
 127   for (unsigned i = 0; i < Libraries.size(); ++i)
 128     if (LinkInLibrary(Libraries[i], is_native))
 129       return true;
 130
 131   // At this point we have processed all the libraries provided to us. Since
 132   // we have an aggregated module at this point, the dependent libraries in
 133   // that module should also be aggregated with duplicates eliminated. This is
 134   // now the time to process the dependent libraries to resolve any remaining
 135   // symbols.
 136   const Module::LibraryListType& DepLibs = Composite->getLibraries();
 137   for (Module::LibraryListType::const_iterator I = DepLibs.begin(),
 138          E = DepLibs.end(); I != E; ++I)
 139     if (LinkInLibrary(*I, is_native))
 140       return true;
 141
 142   return false;
 143 }
 144
 145 /// LinkInFile - opens a bitcode file and links in all objects which
 146 /// provide symbols that are currently undefined.
 147 ///
 148 /// Inputs:
 149 ///  File - The pathname of the bitcode file.
 150 ///
 151 /// Outputs:
 152 ///  ErrorMessage - A C++ string detailing what error occurred, if any.
 153 ///
 154 /// Return Value:
 155 ///  TRUE  - An error occurred.
 156 ///  FALSE - No errors.
 157 ///
 158 bool Linker::LinkInFile(const sys::Path &File, bool &is_native) {
 159   is_native = false;
 160
 161   // Check for a file of name "-", which means "read standard input"
 162   if (File.str() == "-") {
 163     std::auto_ptr<Module> M;
 164     OwningPtr<MemoryBuffer> Buffer;
 165     error_code ec;
 166     if (!(ec = MemoryBuffer::getSTDIN(Buffer))) {
 167       if (!Buffer->getBufferSize()) {
 168         Error = "standard input is empty";
 169       } else {
 170         M.reset(ParseBitcodeFile(Buffer.get(), Context, &Error));
 171         if (M.get())
 172           if (!LinkInModule(M.get(), &Error))
 173             return false;
 174       }
 175     }
 176     return error("Cannot link stdin: " + ec.message());
 177   }
 178
 179   // Determine what variety of file it is.
 180   std::string Magic;
 181   if (!File.getMagicNumber(Magic, 64))
 182     return error("Cannot find linker input '" + File.str() + "'");
 183
 184   switch (sys::IdentifyFileType(Magic.c_str(), 64)) {
 185     default: llvm_unreachable("Bad file type identification");
 186     case sys::Unknown_FileType:
 187       return warning("Ignoring file '" + File.str() +
 188                    "' because does not contain bitcode.");
 189
 190     case sys::Archive_FileType:
 191       // A user may specify an ar archive without -l, perhaps because it
 192       // is not installed as a library. Detect that and link the archive.
 193       if (LinkInArchive(File, is_native))
 194         return true;
 195       break;
 196
 197     case sys::Bitcode_FileType: {
 198       verbose("Linking bitcode file '" + File.str() + "'");
 199       std::auto_ptr<Module> M(LoadObject(File));
 200       if (M.get() == 0)
 201         return error("Cannot load file '" + File.str() + "': " + Error);
 202       if (LinkInModule(M.get(), &Error))
 203         return error("Cannot link file '" + File.str() + "': " + Error);
 204
 205       verbose("Linked in file '" + File.str() + "'");
 206       break;
 207     }
 208
 209     case sys::ELF_Relocatable_FileType:
 210     case sys::ELF_SharedObject_FileType:
 211     case sys::Mach_O_Object_FileType:
 212     case sys::Mach_O_FixedVirtualMemorySharedLib_FileType:
 213     case sys::Mach_O_DynamicallyLinkedSharedLib_FileType:
 214     case sys::Mach_O_DynamicallyLinkedSharedLibStub_FileType:
 215     case sys::COFF_FileType:
 216       is_native = true;
 217       break;
 218   }
 219   return false;
 220 }
 221
 222 /// LinkFiles - takes a module and a list of files and links them all together.
 223 /// It locates the file either in the current directory, as its absolute
 224 /// or relative pathname, or as a file somewhere in LLVM_LIB_SEARCH_PATH.
 225 ///
 226 /// Inputs:
 227 ///  Files      - A vector of sys::Path indicating the LLVM bitcode filenames
 228 ///               to be linked.  The names can refer to a mixture of pure LLVM
 229 ///               bitcode files and archive (ar) formatted files.
 230 ///
 231 /// Return value:
 232 ///  FALSE - No errors.
 233 ///  TRUE  - Some error occurred.
 234 ///
 235 bool Linker::LinkInFiles(const std::vector<sys::Path> &Files) {
 236   bool is_native;
 237   for (unsigned i = 0; i < Files.size(); ++i)
 238     if (LinkInFile(Files[i], is_native))
 239       return true;
 240   return false;
 241 }