From 170fc7cd1811ac3dacc0dd91d36a72440be3a0ae Mon Sep 17 00:00:00 2001
From: Youngsuk Kim <joseph942010@gmail.com>
Date: Tue, 16 Jul 2024 09:45:25 -0400
Subject: [PATCH] [clang] Prevent dangling StringRefs (#98699)

Summary:
Fix locations where dangling StringRefs are created.

* `ConstraintSatisfaction::SubstitutionDiagnostic`: typedef of
`std::pair<SourceLocation, StringRef>`

* `concepts::Requirement::SubstitutionDiagnostic`: struct whose 1st and
3rd data members are `StringRef`s

Fixes #98667

Test Plan:

Reviewers:

Subscribers:

Tasks:

Tags:


Differential Revision: https://phabricator.intern.facebook.com/D59822407
---
 clang/docs/ReleaseNotes.rst               |  2 ++
 clang/lib/Serialization/ASTReaderStmt.cpp | 18 +++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 615e8879ac47441..cb96c5a16f261b7 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -826,6 +826,8 @@ Bug Fixes in This Version
 - ``__is_trivially_equality_comparable`` no longer returns true for types which
   have a constrained defaulted comparison operator (#GH89293).
 
+- Fixed Clang from generating dangling StringRefs when deserializing Exprs & Stmts (#GH98667)
+
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index 37f5c7f2bf20b85..7a3b81fc358acae 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -785,6 +785,12 @@ void ASTStmtReader::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E) {
   E->setRParenLoc(readSourceLocation());
 }
 
+static StringRef saveStrToCtx(const std::string &S, ASTContext &Ctx) {
+  char *Buf = new (Ctx) char[S.size()];
+  std::copy(S.begin(), S.end(), Buf);
+  return StringRef(Buf, S.size());
+}
+
 static ConstraintSatisfaction
 readConstraintSatisfaction(ASTRecordReader &Record) {
   ConstraintSatisfaction Satisfaction;
@@ -795,7 +801,9 @@ readConstraintSatisfaction(ASTRecordReader &Record) {
     for (unsigned i = 0; i != NumDetailRecords; ++i) {
       if (/* IsDiagnostic */Record.readInt()) {
         SourceLocation DiagLocation = Record.readSourceLocation();
-        std::string DiagMessage = Record.readString();
+        StringRef DiagMessage =
+            saveStrToCtx(Record.readString(), Record.getContext());
+
         Satisfaction.Details.emplace_back(
             new (Record.getContext())
                 ConstraintSatisfaction::SubstitutionDiagnostic(DiagLocation,
@@ -820,9 +828,13 @@ void ASTStmtReader::VisitConceptSpecializationExpr(
 
 static concepts::Requirement::SubstitutionDiagnostic *
 readSubstitutionDiagnostic(ASTRecordReader &Record) {
-  std::string SubstitutedEntity = Record.readString();
+  StringRef SubstitutedEntity =
+      saveStrToCtx(Record.readString(), Record.getContext());
+
   SourceLocation DiagLoc = Record.readSourceLocation();
-  std::string DiagMessage = Record.readString();
+  StringRef DiagMessage =
+      saveStrToCtx(Record.readString(), Record.getContext());
+
   return new (Record.getContext())
       concepts::Requirement::SubstitutionDiagnostic{SubstitutedEntity, DiagLoc,
                                                     DiagMessage};