[lld-link] better error message when failing to open archive members

[inglorion]

Summary

The message "could not get the buffer for the member defining symbol"
now also contains the name of the archive and the name of the archive
member that we tried to open.

[inglorion]

Before:

lld-link: error: could not get the buffer for the member defining symbol spvDiagnosticDestroy: No such file or directory

After:

lld-link: error: could not get the buffer for the member defining symbol spvDiagnosticDestroy: obj/third_party/SPIRV-Tools/src/spvtools.lib(obj/third_party/SPIRV-Tools/src/obj/third_party/SPIRV-Tools/src/spvtools/diagnostic.obj): No such file or directory

[inglorion]

(Following the same archive(member) format also used by toString() in InputFiles.cpp)

[ruiu]

lld/COFF/Driver.cpp

228–230 ↗

(On Diff #186038)

I wouldn't pass SymName and ParentName and just capture them using [&].

[inglorion]

Use [=] instead of explicitly passing StringRefs to ReportBufferError.

[inglorion]

lld/COFF/Driver.cpp

228–230 ↗

(On Diff #186038)

[ =] is better for StringRefs, right?

[ruiu]

LGTM

lld/trunk/COFF/Driver.cpp

void LinkerDriver::addArchiveBuffer(MemoryBufferRef MB, StringRef SymName,
   Obj->ParentName = ParentName;
   Symtab->addFile(Obj);
   log("Loaded " + toString(Obj) + " for " + SymName);
 }
 
 void LinkerDriver::enqueueArchiveMember(const Archive::Child &C,
                                         StringRef SymName,
                                         StringRef ParentName) {
+
+  auto ReportBufferError = [=](Error &&E,
+                              StringRef ChildName) {
+    fatal("could not get the buffer for the member defining symbol " +
+          SymName + ": " + ParentName + "(" + ChildName + "): " +
+          toString(std::move(E)));
+  };
+
   if (!C.getParent()->isThin()) {
-    MemoryBufferRef MB = CHECK(
-        C.getMemoryBufferRef(),
-        "could not get the buffer for the member defining symbol " + SymName);
+    Expected<MemoryBufferRef> MBOrErr = C.getMemoryBufferRef();
+    if (!MBOrErr)
+      ReportBufferError(MBOrErr.takeError(), check(C.getFullName()));
+    MemoryBufferRef MB = MBOrErr.get();
     enqueueTask([=]() { Driver->addArchiveBuffer(MB, SymName, ParentName); });
     return;
   }
 
-  auto Future = std::make_shared<std::future<MBErrPair>>(createFutureForFile(
-      CHECK(C.getFullName(),
-            "could not get the filename for the member defining symbol " +
-                SymName)));
+  std::string ChildName = CHECK(
+      C.getFullName(),
+      SymName);
+  auto Future = std::make_shared<std::future<MBErrPair>>(
+      createFutureForFile(ChildName));
   enqueueTask([=]() {
     auto MBOrErr = Future->get();
     if (MBOrErr.second)
-      fatal("could not get the buffer for the member defining " + SymName +
-            ": " + MBOrErr.second.message());
+      ReportBufferError(errorCodeToError(MBOrErr.second), ChildName);
     Driver->addArchiveBuffer(takeBuffer(std::move(MBOrErr.first)), SymName,
                              ParentName);
   });
 }
 
 static bool isDecorated(StringRef Sym) {
   return Sym.startswith("@") || Sym.contains("@@") || Sym.startswith("?") ||
          (!Config->MinGW && Sym.contains('@'));