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

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

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

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

[ruiu]

LGTM.

include/lld/ReaderWriter/ELFLinkingContext.h

272

Don't make a function virtual if not needed.

unittests/DriverTests/GnuLdDriverTest.cpp

184

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.

include/lld/ReaderWriter/ELFLinkingContext.h

     return true;
   }
 
+  // Retrieve search path list.
+  virtual 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.

lib/Driver/GnuLdDriver.cpp

   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();
 }
 

unittests/DriverTests/GnuLdDriverTest.cpp

   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(\"/usr/lib\")", "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("/usr/lib", searchPaths[1]);
+}