[BinaryFormat] Teach identify_magic about Tapi files.

Summary:
Tapi files are YAML files that start with the !tapi tag. The only execption are
TBD v1 files, which don't have a tag. In that case we have to scan a little
further and check if the first key "archs" exists.

This is the first patch in a series of patches to add libObject support for
text-based dynamic library (.tbd) files.

This patch is practically exactly the same as D37820, that was never pushed to master,
and is needed for future commits related to reading tbd files for llvm-nm

Reviewers: ributzka, steven_wu, bollu, espindola, jfb, shafik, jdoerfert

Reviewed By: steven_wu

Subscribers: dexonsmith, llvm-commits

Tags: #llvm, #clang, #sanitizers, #lldb, #libc, #openmp

Differential Revision: https://reviews.llvm.org/D66149

llvm-svn: 369579

include/llvm/BinaryFormat/Magic.h

@@ -49,6 +49,7 @@ struct file_magic {
     xcoff_object_64,     ///< 64-bit XCOFF object file
     wasm_object,         ///< WebAssembly Object file
     pdb,                 ///< Windows PDB debug info file
+    tapi_file,           ///< Text-based Dynamic Library Stub file
   };
 
   bool is_object() const { return V != unknown; }

lib/BinaryFormat/Magic.cpp

@@ -210,6 +210,11 @@ file_magic llvm::identify_magic(StringRef Magic) {
       return file_magic::coff_object;
     break;
 
+  case 0x2d: // YAML '-'
+    if (startswith(Magic, "--- !tapi") || startswith(Magic, "---\narchs:"))
+      return file_magic::tapi_file;
+    break;
+
   default:
     break;
   }

lib/Object/Binary.cpp

@@ -86,6 +86,9 @@ Expected<std::unique_ptr<Binary>> object::createBinary(MemoryBufferRef Buffer,
     return errorCodeToError(object_error::invalid_file_type);
   case file_magic::minidump:
     return MinidumpFile::create(Buffer);
+  case file_magic::tapi_file:
+    // Placeholder until TAPI is supported for lib/Object
+    return errorCodeToError(object_error::invalid_file_type);
   }
   llvm_unreachable("Unexpected Binary File Type");
 }

lib/Object/ObjectFile.cpp

@@ -127,6 +127,8 @@ ObjectFile::createObjectFile(MemoryBufferRef Object, file_magic Type) {
   case file_magic::pdb:
   case file_magic::minidump:
     return errorCodeToError(object_error::invalid_file_type);
+  case file_magic::tapi_file:
+    return errorCodeToError(object_error::invalid_file_type);
   case file_magic::elf:
   case file_magic::elf_relocatable:
   case file_magic::elf_executable:

lib/Object/SymbolicFile.cpp

@@ -53,6 +53,7 @@ SymbolicFile::createSymbolicFile(MemoryBufferRef Object, file_magic Type,
   case file_magic::windows_resource:
   case file_magic::pdb:
   case file_magic::minidump:
+  case file_magic::tapi_file:
     return errorCodeToError(object_error::invalid_file_type);
   case file_magic::elf:
   case file_magic::elf_executable:

unittests/BinaryFormat/TestFileMagic.cpp

@@ -82,6 +82,8 @@ const char macho_dynamically_linked_shared_lib_stub[] =
 const char ms_dos_stub_broken[] = "\x4d\x5a\x20\x20";
 const char pdb[] = "Microsoft C/C++ MSF 7.00\r\n\x1a"
                    "DS\x00\x00\x00";
+const char tapi_file[] = "--- !tapi-tbd-v1\n";
+const char tapi_file_tbd_v1[] = "---\narchs: [";
 
 TEST_F(MagicTest, Magic) {
   struct type {
@@ -114,6 +116,9 @@ TEST_F(MagicTest, Magic) {
       DEFINE(pdb),
       {"ms_dos_stub_broken", ms_dos_stub_broken, sizeof(ms_dos_stub_broken),
        file_magic::unknown},
+      DEFINE(tapi_file),
+      {"tapi_file_tbd_v1", tapi_file_tbd_v1, sizeof(tapi_file_tbd_v1),
+       file_magic::tapi_file},
 #undef DEFINE
   };