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 ↗

(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.

lib/Driver/GnuLdDriver.cpp

 }
 
 static std::error_code
+evaluateLinkerScriptSearchDir(ELFLinkingContext &ctx,
+                              const script::SearchDir *searchDir)
+{
+
+  ctx.addSearchPath(searchDir->getSearchPath());
+  return std::error_code();
+}
+
+static std::error_code
 evaluateLinkerScript(ELFLinkingContext &ctx, StringRef path,
                      raw_ostream &diag) {
   // Read the script file from disk and parse.

     return LinkerScriptReaderError::parse_error;
 
   // Evaluate script commands.
-  // Currently we only recognize GROUP() command.
-  for (const script::Command *c : script->_commands)
+  // Currently we only recognize a subset of the 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))
+      if (std::error_code ec = evaluateLinkerScriptSearchDir(ctx, searchDir))
+        return ec;
+   }
   return std::error_code();
 }