[dsymutil] Remove paper trail warnings

Remove the paper trail warning from dsymutil and the DWARF linker. The
original purpose of this functionality was to leave a paper trail in the
output artifact about missing object files. The current implementation
however has diverged and is the source of a pretty serious bug:

  - In the debug map parser, missing object files are not the only
    warnings we emit. When paper trail warnings are enabled, all of them
    end up in the dSYM which wasn't the goal.
  - When warnings are associated with a object file in the debug map, it
    is skipped by the DWARF linker. This only makes sense if the object
    file is missing and is obviously incorrect for any other type of
    warning (such as a missing symbol).

The combination of the two means that we can generate broken DWARF when
the feature is enabled. AFAIK it was only used by Apple and nobody I
spoke to has relied on it, so rather than fixing the broken behavior I
propose we remove it.

Author: JDevlieghere

llvm/test/tools/dsymutil/X86/papertrail-warnings.test

@@ -27,11 +27,9 @@ class MachODebugMapParser {
 public:
   MachODebugMapParser(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
                       StringRef BinaryPath, ArrayRef<std::string> Archs,
-                      StringRef PathPrefix = "",
-                      bool PaperTrailWarnings = false, bool Verbose = false)
+                      StringRef PathPrefix = "", bool Verbose = false)
       : BinaryPath(std::string(BinaryPath)), Archs(Archs.begin(), Archs.end()),
-        PathPrefix(std::string(PathPrefix)),
-        PaperTrailWarnings(PaperTrailWarnings), BinHolder(VFS, Verbose),
+        PathPrefix(std::string(PathPrefix)), BinHolder(VFS, Verbose),
         CurrentDebugMapObject(nullptr), SkipDebugMapObject(false) {}
 
   /// Parses and returns the DebugMaps of the input binary. The binary contains
@@ -49,7 +47,6 @@ class MachODebugMapParser {
   std::string BinaryPath;
   SmallVector<StringRef, 1> Archs;
   std::string PathPrefix;
-  bool PaperTrailWarnings;
 
   /// Owns the MemoryBuffer for the main binary.
   BinaryHolder BinHolder;
@@ -136,13 +133,6 @@ class MachODebugMapParser {
                          << MachOUtils::getArchName(
                                 Result->getTriple().getArchName())
                          << ") " << File << " " << Msg << "\n";
-
-    if (PaperTrailWarnings) {
-      if (!File.empty())
-        Result->addDebugMapObject(File, sys::TimePoint<std::chrono::seconds>());
-      if (Result->end() != Result->begin())
-        (*--Result->end())->addWarning(Msg.str());
-    }
   }
 };
 
@@ -702,13 +692,11 @@ namespace dsymutil {
 llvm::ErrorOr<std::vector<std::unique_ptr<DebugMap>>>
 parseDebugMap(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
               StringRef InputFile, ArrayRef<std::string> Archs,
-              StringRef PrependPath, bool PaperTrailWarnings, bool Verbose,
-              bool InputIsYAML) {
+              StringRef PrependPath, bool Verbose, bool InputIsYAML) {
   if (InputIsYAML)
     return DebugMap::parseYAMLDebugMap(InputFile, PrependPath, Verbose);
 
-  MachODebugMapParser Parser(VFS, InputFile, Archs, PrependPath,
-                             PaperTrailWarnings, Verbose);
+  MachODebugMapParser Parser(VFS, InputFile, Archs, PrependPath, Verbose);
   return Parser.parse();
 }
 

llvm/tools/dsymutil/MachODebugMapParser.cpp

@@ -102,7 +102,6 @@ struct DsymutilOptions {
   bool DumpStab = false;
   bool Flat = false;
   bool InputIsYAMLDebugMap = false;
-  bool PaperTrailWarnings = false;
   bool ForceKeepFunctionForStatic = false;
   std::string SymbolMap;
   std::string OutputFile;
@@ -193,11 +192,6 @@ static Error verifyOptions(const DsymutilOptions &Options) {
         "cannot use -o with multiple inputs in flat mode.",
         errc::invalid_argument);
 
-  if (Options.PaperTrailWarnings && Options.InputIsYAMLDebugMap)
-    return make_error<StringError>(
-        "paper trail warnings are not supported for YAML input.",
-        errc::invalid_argument);
-
   if (!Options.ReproducerPath.empty() &&
       Options.ReproMode != ReproducerMode::Use)
     return make_error<StringError>(
@@ -281,7 +275,6 @@ static Expected<DsymutilOptions> getOptions(opt::InputArgList &Args) {
   Options.DumpStab = Args.hasArg(OPT_symtab);
   Options.Flat = Args.hasArg(OPT_flat);
   Options.InputIsYAMLDebugMap = Args.hasArg(OPT_yaml_input);
-  Options.PaperTrailWarnings = Args.hasArg(OPT_papertrail);
 
   if (Expected<DWARFVerify> Verify = getVerifyKind(Args)) {
     Options.Verify = *Verify;
@@ -360,9 +353,6 @@ static Expected<DsymutilOptions> getOptions(opt::InputArgList &Args) {
   if (Options.DumpDebugMap || Options.LinkOpts.Verbose)
     Options.LinkOpts.Threads = 1;
 
-  if (getenv("RC_DEBUG_OPTIONS"))
-    Options.PaperTrailWarnings = true;
-
   if (opt::Arg *RemarksPrependPath = Args.getLastArg(OPT_remarks_prepend_path))
     Options.LinkOpts.RemarksPrependPath = RemarksPrependPath->getValue();
 
@@ -625,8 +615,8 @@ int dsymutil_main(int argc, char **argv) {
 
     auto DebugMapPtrsOrErr =
         parseDebugMap(Options.LinkOpts.VFS, InputFile, Options.Archs,
-                      Options.LinkOpts.PrependPath, Options.PaperTrailWarnings,
-                      Options.LinkOpts.Verbose, Options.InputIsYAMLDebugMap);
+                      Options.LinkOpts.PrependPath, Options.LinkOpts.Verbose,
+                      Options.InputIsYAMLDebugMap);
 
     if (auto EC = DebugMapPtrsOrErr.getError()) {
       WithColor::error() << "cannot parse the debug map for '" << InputFile

llvm/tools/dsymutil/dsymutil.cpp

@@ -37,8 +37,7 @@ class BinaryHolder;
 ErrorOr<std::vector<std::unique_ptr<DebugMap>>>
 parseDebugMap(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
               StringRef InputFile, ArrayRef<std::string> Archs,
-              StringRef PrependPath, bool PaperTrailWarnings, bool Verbose,
-              bool InputIsYAML);
+              StringRef PrependPath, bool Verbose, bool InputIsYAML);
 
 /// Dump the symbol table.
 bool dumpStab(llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,