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