[DebugInfo] Pass string ownership to MarkupFilter (#75403)

Last `getline` call destroys `InputString`, and `finish` accesses dead
`StringRef`.

Detected with #72677.

Fixes
https://lab.llvm.org/buildbot/#/builders/sanitizer-x86_64-linux-fast

Author: vitalybuka

llvm/include/llvm/DebugInfo/Symbolize/MarkupFilter.h

@@ -39,7 +39,7 @@ class MarkupFilter {
   ///
   /// Invalid or unimplemented markup elements are removed. Some output may be
   /// deferred until future filter() or finish() call.
-  void filter(StringRef Line);
+  void filter(std::string &&InputLine);
 
   /// Records that the input stream has ended and writes any deferred output.
   void finish();
@@ -142,7 +142,7 @@ class MarkupFilter {
   MarkupParser Parser;
 
   // Current line being filtered.
-  StringRef Line;
+  std::string Line;
 
   // A module info line currently being built. This incorporates as much mmap
   // information as possible before being emitted.

llvm/lib/DebugInfo/Symbolize/MarkupFilter.cpp

@@ -41,8 +41,8 @@ MarkupFilter::MarkupFilter(raw_ostream &OS, LLVMSymbolizer &Symbolizer,
       ColorsEnabled(
           ColorsEnabled.value_or(WithColor::defaultAutoDetectFunction()(OS))) {}
 
-void MarkupFilter::filter(StringRef Line) {
-  this->Line = Line;
+void MarkupFilter::filter(std::string &&InputLine) {
+  Line = std::move(InputLine);
   resetColor();
 
   Parser.parseLine(Line);
@@ -695,7 +695,9 @@ void MarkupFilter::reportTypeError(StringRef Str, StringRef TypeName) const {
 // passed to beginLine().
 void MarkupFilter::reportLocation(StringRef::iterator Loc) const {
   errs() << Line;
-  WithColor(errs().indent(Loc - Line.begin()), HighlightColor::String) << '^';
+  WithColor(errs().indent(Loc - StringRef(Line).begin()),
+            HighlightColor::String)
+      << '^';
   errs() << '\n';
 }
 
@@ -741,7 +743,7 @@ uint64_t MarkupFilter::adjustAddr(uint64_t Addr, PCType Type) const {
 }
 
 StringRef MarkupFilter::lineEnding() const {
-  return Line.ends_with("\r\n") ? "\r\n" : "\n";
+  return StringRef(Line).ends_with("\r\n") ? "\r\n" : "\n";
 }
 
 bool MarkupFilter::MMap::contains(uint64_t Addr) const {

llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp

@@ -430,7 +430,7 @@ static void filterMarkup(const opt::InputArgList &Args, LLVMSymbolizer &Symboliz
   std::string InputString;
   while (std::getline(std::cin, InputString)) {
     InputString += '\n';
-    Filter.filter(InputString);
+    Filter.filter(std::move(InputString));
   }
   Filter.finish();
 }