[lld-link] Add context-aware diagnostic functions (#118430)

Similar to #112319 for ELF. While there is some initial boilerplate, it
can simplify some call sites that use Twine, especially when a printed
element uses `ctx` or toString.

lld/COFF/Config.h

@@ -9,6 +9,7 @@
 #ifndef LLD_COFF_CONFIG_H
 #define LLD_COFF_CONFIG_H
 
+#include "lld/Common/ErrorHandler.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallVector.h"
@@ -27,6 +28,7 @@ namespace lld::coff {
 using llvm::COFF::IMAGE_FILE_MACHINE_UNKNOWN;
 using llvm::COFF::WindowsSubsystem;
 using llvm::StringRef;
+class COFFLinkerContext;
 class DefinedAbsolute;
 class StringChunk;
 class Symbol;
@@ -332,6 +334,48 @@ struct Configuration {
   BuildIDHash buildIDHash = BuildIDHash::None;
 };
 
+struct COFFSyncStream : SyncStream {
+  COFFLinkerContext &ctx;
+  COFFSyncStream(COFFLinkerContext &ctx, DiagLevel level);
+};
+
+template <typename T>
+std::enable_if_t<!std::is_pointer_v<std::remove_reference_t<T>>,
+                 const COFFSyncStream &>
+operator<<(const COFFSyncStream &s, T &&v) {
+  s.os << std::forward<T>(v);
+  return s;
+}
+
+inline const COFFSyncStream &operator<<(const COFFSyncStream &s,
+                                        const char *v) {
+  s.os << v;
+  return s;
+}
+
+inline const COFFSyncStream &operator<<(const COFFSyncStream &s, Error v) {
+  s.os << llvm::toString(std::move(v));
+  return s;
+}
+
+// Report a log if -verbose is specified.
+COFFSyncStream Log(COFFLinkerContext &ctx);
+
+// Print a message to stdout.
+COFFSyncStream Msg(COFFLinkerContext &ctx);
+
+// Report a warning. Upgraded to an error if /WX is specified.
+COFFSyncStream Warn(COFFLinkerContext &ctx);
+
+// Report an error that will suppress the output file generation.
+COFFSyncStream Err(COFFLinkerContext &ctx);
+
+// Report a fatal error that exits immediately. This should generally be avoided
+// in favor of Err.
+COFFSyncStream Fatal(COFFLinkerContext &ctx);
+
+uint64_t errCount(COFFLinkerContext &ctx);
+
 } // namespace lld::coff
 
 #endif

lld/COFF/Driver.cpp

@@ -56,11 +56,33 @@
 #include <optional>
 #include <tuple>
 
+using namespace lld;
+using namespace lld::coff;
 using namespace llvm;
 using namespace llvm::object;
 using namespace llvm::COFF;
 using namespace llvm::sys;
 
+COFFSyncStream::COFFSyncStream(COFFLinkerContext &ctx, DiagLevel level)
+    : SyncStream(ctx.e, level), ctx(ctx) {}
+
+COFFSyncStream coff::Log(COFFLinkerContext &ctx) {
+  return {ctx, DiagLevel::Log};
+}
+COFFSyncStream coff::Msg(COFFLinkerContext &ctx) {
+  return {ctx, DiagLevel::Msg};
+}
+COFFSyncStream coff::Warn(COFFLinkerContext &ctx) {
+  return {ctx, DiagLevel::Warn};
+}
+COFFSyncStream coff::Err(COFFLinkerContext &ctx) {
+  return {ctx, DiagLevel::Err};
+}
+COFFSyncStream coff::Fatal(COFFLinkerContext &ctx) {
+  return {ctx, DiagLevel::Fatal};
+}
+uint64_t coff::errCount(COFFLinkerContext &ctx) { return ctx.e.errorCount; }
+
 namespace lld::coff {
 
 bool link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
@@ -75,7 +97,7 @@ bool link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
 
   ctx->driver.linkerMain(args);
 
-  return errorCount() == 0;
+  return errCount(*ctx) == 0;
 }
 
 // Parse options of the form "old;new".
@@ -212,7 +234,8 @@ void LinkerDriver::addBuffer(std::unique_ptr<MemoryBuffer> mb,
     ctx.symtab.addFile(make<PDBInputFile>(ctx, mbref));
     break;
   case file_magic::coff_cl_gl_object:
-    error(filename + ": is not a native COFF file. Recompile without /GL");
+    Err(ctx) << filename
+             << ": is not a native COFF file. Recompile without /GL";
     break;
   case file_magic::pecoff_executable:
     if (ctx.config.mingw) {
@@ -302,7 +325,7 @@ void LinkerDriver::addArchiveBuffer(MemoryBufferRef mb, StringRef symName,
 
   obj->parentName = parentName;
   ctx.symtab.addFile(obj);
-  log("Loaded " + toString(obj) + " for " + symName);
+  Log(ctx) << "Loaded " << obj << " for " << symName;
 }
 
 void LinkerDriver::enqueueArchiveMember(const Archive::Child &c,
@@ -310,9 +333,9 @@ void LinkerDriver::enqueueArchiveMember(const Archive::Child &c,
                                         StringRef parentName) {
 
   auto reportBufferError = [=](Error &&e, StringRef childName) {
-    fatal("could not get the buffer for the member defining symbol " +
-          toCOFFString(ctx, sym) + ": " + parentName + "(" + childName +
-          "): " + toString(std::move(e)));
+    Fatal(ctx) << "could not get the buffer for the member defining symbol "
+               << &sym << ": " << parentName << "(" << childName
+               << "): " << std::move(e);
   };
 
   if (!c.getParent()->isThin()) {
@@ -361,7 +384,7 @@ void LinkerDriver::parseDirectives(InputFile *file) {
   if (s.empty())
     return;
 
-  log("Directives: " + toString(file) + ": " + s);
+  Log(ctx) << "Directives: " << file << ": " << s;
 
   ArgParser parser(ctx);
   // .drectve is always tokenized using Windows shell rules.
@@ -414,7 +437,7 @@ void LinkerDriver::parseDirectives(InputFile *file) {
       break;
     case OPT_entry:
       if (!arg->getValue()[0])
-        fatal("missing entry point symbol name");
+        Fatal(ctx) << "missing entry point symbol name";
       ctx.config.entry = addUndefined(mangle(arg->getValue()), true);
       break;
     case OPT_failifmismatch:
@@ -779,7 +802,7 @@ StringRef LinkerDriver::findDefaultEntry() {
     if (findUnderscoreMangle("wWinMain")) {
       if (!findUnderscoreMangle("WinMain"))
         return mangle("wWinMainCRTStartup");
-      warn("found both wWinMain and WinMain; using latter");
+      Warn(ctx) << "found both wWinMain and WinMain; using latter";
     }
     return mangle("WinMainCRTStartup");
   }
@@ -2200,7 +2223,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
     config->incremental = false;
   }
 
-  if (errorCount())
+  if (errCount(ctx))
     return;
 
   std::set<sys::fs::UniqueID> wholeArchives;
@@ -2279,7 +2302,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
       stream << "  " << path << "\n";
     }
 
-    message(buffer);
+    Msg(ctx) << buffer;
   }
 
   // Process files specified as /defaultlib. These must be processed after

lld/COFF/InputFiles.cpp

@@ -70,6 +70,11 @@ std::string lld::toString(const coff::InputFile *file) {
       .str();
 }
 
+const COFFSyncStream &coff::operator<<(const COFFSyncStream &s,
+                                       const InputFile *f) {
+  return s << toString(f);
+}
+
 /// Checks that Source is compatible with being a weak alias to Target.
 /// If Source is Undefined and has no weak alias set, makes it a weak
 /// alias to Target.

lld/COFF/InputFiles.h

@@ -40,6 +40,8 @@ class DWARFCache;
 namespace coff {
 class COFFLinkerContext;
 
+const COFFSyncStream &operator<<(const COFFSyncStream &, const InputFile *);
+
 std::vector<MemoryBufferRef> getArchiveMembers(llvm::object::Archive *file);
 
 using llvm::COFF::IMAGE_FILE_MACHINE_UNKNOWN;

lld/COFF/Symbols.cpp

@@ -53,6 +53,13 @@ std::string toCOFFString(const COFFLinkerContext &ctx,
   return maybeDemangleSymbol(ctx, b.getName());
 }
 
+const COFFSyncStream &
+coff::operator<<(const COFFSyncStream &s,
+                 const llvm::object::Archive::Symbol *sym) {
+  s << maybeDemangleSymbol(s.ctx, sym->getName());
+  return s;
+}
+
 namespace coff {
 
 void Symbol::computeName() {

lld/COFF/Symbols.h

@@ -35,6 +35,9 @@ class InputFile;
 class ObjFile;
 class SymbolTable;
 
+const COFFSyncStream &operator<<(const COFFSyncStream &,
+                                 const llvm::object::Archive::Symbol *);
+
 // The base class for real symbol classes.
 class Symbol {
 public: