[LLD][COFF] Convert file name to lowercase when inserting it into visitedLibs

[pzheng]

Summary

It seems to be a bug in LinkerDriver::findFile, the file name is not converted
to lowercase when being inserted into visitedLibs. This is the only exception
in the file and all other places always convert file names to lowercase when
inserting them into visitedLibs (or visitedFiles).

[hans]

Looks right to me. Should there be a test for this?

[thieta]

Yep seems correct to me as well - but I think we need a test.

[pzheng]

Add a test case

[pzheng]

Thanks for the feedback, @hans and @thieta. I have added a test case which can trigger the bug.

[thieta]

Thanks for the test - but I am not sure it should be a part of nodefaultlib? Is there a reason you didn't add it as it's own test?

[pzheng]

I guess it's a little weird to piggyback the test into nodefaultlib.test. :) Will put it into a new test instead.

[pzheng]

Create a new test

[pzheng]

Fix a typo

[thieta]

Thanks for the patch! Wait for Hans to give his approval as well before committing.

[hans]

lgtm

lld/COFF/Driver.cpp

Optional<StringRef> LinkerDriver::findFile(StringRef filename) {
 
   if (Optional<sys::fs::UniqueID> id = getUniqueID(path)) {
     bool seen = !visitedFiles.insert(*id).second;
     if (seen)
       return None;
   }
 
   if (path.endswith_insensitive(".lib"))
-    visitedLibs.insert(std::string(sys::path::filename(path)));
+    visitedLibs.insert(std::string(sys::path::filename(path).lower()));
   return path;
 }
 
 // MinGW specific. If an embedded directive specified to link to
 // foo.lib, but it isn't found, try libfoo.a instead.
 StringRef LinkerDriver::doFindLibMinGW(StringRef filename) {
   if (filename.contains('/') || filename.contains('\\'))
     return filename;

lld/test/COFF/visitedlibs.test

+# RUN: rm -rf %t && mkdir -p %t
+# RUN: cp %S/Inputs/hello64.obj %t
+# RUN: cp %S/Inputs/std64.lib %t/STD64.lib
+
+# RUN: lld-link %t/STD64.lib /out:%t.exe /entry:main \
+# RUN:   /subsystem:console %t/hello64.obj /defaultlib:STD64.lib \
+# RUN:   /verbose 2>&1 | FileCheck %s
+
+CHECK: Reading {{.*}}/STD64.lib
+CHECK-NOT: could not open 'STD64.lib'