[clang-format] Avoid crash in LevelIndentTracker.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/56352.

[MyDeveloperDay]

LGTM

[owenpan]

clang/lib/Format/UnwrappedLineFormatter.cpp

68–69

You can delete both lines as the body of the if statement is unreachable. (After the while loop on lines 62-63, IndentForLevel.size() is larger than Line.Level.)

[HazardyKnusperkeks]

clang/lib/Format/UnwrappedLineFormatter.cpp

62–69

So how about that?

[owenpan]

clang/lib/Format/UnwrappedLineFormatter.cpp

62–69

Good idea, but it's an unrelated change. Let's take care of it in D129105, which I will update to use resize() instead of insert().

[curdeius]

Address comments.

clang/lib/Format/UnwrappedLineFormatter.cpp

public:
   unsigned getIndent() const { return Indent; }
 
   /// Update the indent state given that \p Line is going to be formatted
   /// next.
   void nextLine(const AnnotatedLine &Line) {
     Offset = getIndentOffset(*Line.First);
     // Update the indent level cache size so that we can rely on it
     // having the right size in adjustToUnmodifiedline.
     while (IndentForLevel.size() <= Line.Level)
       IndentForLevel.push_back(-1);
     if (Line.InPPDirective) {
       unsigned IndentWidth =
           (Style.PPIndentWidth >= 0) ? Style.PPIndentWidth : Style.IndentWidth;
       Indent = Line.Level * IndentWidth + AdditionalIndent;
     } else {
-      IndentForLevel.resize(Line.Level + 1);
       Indent = getIndent(Line.Level);
     }
     if (static_cast<int>(Indent) + Offset >= 0)
       Indent += Offset;
     if (Line.First->is(TT_CSharpGenericTypeConstraint))
       Indent = Line.Level * Style.IndentWidth + Style.ContinuationIndentWidth;
   }
 
   /// Update the indent state given that \p Line indent should be
   /// skipped.
   void skipLine(const AnnotatedLine &Line) {
     while (IndentForLevel.size() <= Line.Level)
       IndentForLevel.push_back(Indent);
   }
 
   /// Update the level indent to adapt to the given \p Line.
   ///
   /// When a line is not formatted, we move the subsequent lines on the same
   /// level to the same indent.
   /// Note that \c nextLine must have been called before this method.
   void adjustToUnmodifiedLine(const AnnotatedLine &Line) {
     unsigned LevelIndent = Line.First->OriginalColumn;
     if (static_cast<int>(LevelIndent) - Offset >= 0)
       LevelIndent -= Offset;
+    assert(Line.Level < IndentForLevel.size());
     if ((!Line.First->is(tok::comment) || IndentForLevel[Line.Level] == -1) &&
         !Line.InPPDirective) {
       IndentForLevel[Line.Level] = LevelIndent;
     }
   }
 
 private:
   /// Get the offset of the line relatively to the level.

clang/unittests/Format/FormatTestSelective.cpp

 }
 
 TEST_F(FormatTestSelective, DontAssert) {
   // https://llvm.org/PR53880
   std::string Code = "void f() {\n"
                      "  return a == 8 ? 32 : 16;\n"
                      "}\n";
   EXPECT_EQ(Code, format(Code, 40, 0));
+
+  // https://llvm.org/PR56352
+  Style.CompactNamespaces = true;
+  Style.NamespaceIndentation = FormatStyle::NI_All;
+  Code = "\n"
+         "namespace ns1 { namespace ns2 {\n"
+         "}}";
+  EXPECT_EQ(Code, format(Code, 0, 0));
 }
 
 } // end namespace
 } // end namespace format
 } // end namespace clang