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