Implement semantic action for SEARCH_DIR linker script command

[davide]

Summary

The title says almost everything. As a side note, this is needed, among others by the FreeBSD kernel linker script.

[emaste]

lib/Driver/GnuLdDriver.cpp

293–295 ↗

(On Diff #18802)

To me this comment implies we recognize a subset of GROUP() and SEARCH_DIR().

Maybe Currently we only recognize this subset of linker script commands:

[ruiu]

I just committed r227341 to test the existing linker script functionality. Please add a test in the same way as my commit for this patch too.

lib/Driver/GnuLdDriver.cpp

276 ↗

(On Diff #18802)

This function will never fail and it's too simple to be a separate function -- it's just one line. I'd write it in-line.

[davide]

Attempt to write an unit test and address Ed's and Rui's comments.

[emaste]

lib/Driver/GnuLdDriver.cpp

290 ↗

(On Diff #18937)

phabricator often has trouble rendering whitespace properly, but please double-check tabs vs spaces here

[ruiu]

LGTM.

include/lld/ReaderWriter/ELFLinkingContext.h

272 ↗

(On Diff #18937)

Don't make a function virtual if not needed.

unittests/DriverTests/GnuLdDriverTest.cpp

184 ↗

(On Diff #18937)

I think there's code in the GNU driver to add /usr/lib to the default search path, so this test may pass even if the linker script parser doesn't work. I'd make it something unrealistic, like "/foo/bar", to avoid possible conflict.

lld/trunk/include/lld/ReaderWriter/ELFLinkingContext.h

public:
   }
 
   // add search path to list.
   virtual bool addSearchPath(StringRef ref) {
     _inputSearchPaths.push_back(ref);
     return true;
   }
 
+  // Retrieve search path list.
+  StringRefVector getSearchPaths() { return _inputSearchPaths; };
+
   // By default, the linker would merge sections that are read only with
   // segments that have read and execute permissions. When the user specifies a
   // flag --rosegment, a separate segment needs to be created.
   bool mergeRODataToTextSegment() const { return _mergeRODataToTextSegment; }
 
   void setCreateSeparateROSegment() { _mergeRODataToTextSegment = false; }
 
   bool isDynamicallyExportedSymbol(StringRef name) const {

lld/trunk/lib/Driver/GnuLdDriver.cpp

GnuLdDriver::evalLinkerScript(ELFLinkingContext &ctx,
   // Read the script file from disk and parse.
   StringRef path = mb->getBufferIdentifier();
   auto lexer = llvm::make_unique<script::Lexer>(std::move(mb));
   auto parser = llvm::make_unique<script::Parser>(*lexer);
   script::LinkerScript *script = parser->parse();
   if (!script)
     return LinkerScriptReaderError::parse_error;
   // Evaluate script commands.
-  // Currently we only recognize GROUP() command.
-  for (const script::Command *c : script->_commands)
+  // Currently we only recognize this subset of linker script commands:
+  // - GROUP()
+  // - SEARCH_DIR()
+  for (const script::Command *c : script->_commands) {
     if (auto *group = dyn_cast<script::Group>(c))
       if (std::error_code ec = evaluateLinkerScriptGroup(ctx, path, group, diag))
         return ec;
+    if (auto *searchDir = dyn_cast<script::SearchDir>(c))
+      ctx.addSearchPath(searchDir->getSearchPath());
+  }
   return std::error_code();
 }
 
 bool GnuLdDriver::applyEmulation(llvm::Triple &triple,
                                  llvm::opt::InputArgList &args,
                                  raw_ostream &diag) {
   llvm::opt::Arg *arg = args.getLastArg(OPT_m);
   if (!arg)

lld/trunk/unittests/DriverTests/GnuLdDriverTest.cpp

std::error_code ec = GnuLdDriver::evalLinkerScript(
     *_context, std::move(mb), out);
   EXPECT_FALSE(ec);
   std::vector<std::unique_ptr<Node>> &nodes = _context->getNodes();
   EXPECT_EQ((size_t)4, nodes.size());
   EXPECT_EQ("/x", cast<FileNode>(nodes[1].get())->getFile()->path());
   EXPECT_EQ("/y", cast<FileNode>(nodes[2].get())->getFile()->path());
   EXPECT_EQ(2, cast<GroupEnd>(nodes[3].get())->getSize());
 }
+
+TEST_F(GnuLdParserTest, LinkerScriptSearchDir) {
+  parse("ld", "a.o", nullptr);
+  std::unique_ptr<MemoryBuffer> mb = MemoryBuffer::getMemBuffer(
+    "SEARCH_DIR(\"/foo/bar\")", "foo.so");
+  std::string s;
+  raw_string_ostream out(s);
+  std::error_code ec = GnuLdDriver::evalLinkerScript(
+    *_context, std::move(mb), out);
+  EXPECT_FALSE(ec);
+  std::vector<StringRef> searchPaths = _context->getSearchPaths();
+  EXPECT_EQ((size_t)2, searchPaths.size());
+  EXPECT_EQ("/foo/bar", searchPaths[1]);
+}