[PATCH] D127183: [clang-format] Skip parsing a block if it's nested too deep

[Owen Pan via Phabricator via cfe-commits]

owenpan created this revision.
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Don't parse blocks that are nested hundreds of levels deep, e.g., 
https://github.com/llvm/llvm-project/blob/a7b154aa1770a2223be2e99735fab54c1c081007/clang/test/Parser/parser_overflow.c#L11.

Adding a pointer parameter to each of `parseLevel()` and `parseBlock()` would 
overflow the stack when formatting clang/test/Parser/parser_overflow.c, so 
adding an upper bound to the number of levels of nested blocks will provide a 
safeguard.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127183

Files:
  clang/lib/Format/UnwrappedLineParser.cpp


Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -837,6 +837,10 @@
   unsigned InitialLevel = Line->Level;
   nextToken(/*LevelDifference=*/AddLevels);
 
+  // Bail out if there are too many levels. Otherwise, the stack might 
overflow.
+  if (Line->Level > 300)
+    return IfStmtKind::NotIf;
+
   if (MacroBlock && FormatTok->is(tok::l_paren))
     parseParens();
 



Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -837,6 +837,10 @@
   unsigned InitialLevel = Line->Level;
   nextToken(/*LevelDifference=*/AddLevels);
 
+  // Bail out if there are too many levels. Otherwise, the stack might overflow.
+  if (Line->Level > 300)
+    return IfStmtKind::NotIf;
+
   if (MacroBlock && FormatTok->is(tok::l_paren))
     parseParens();
 

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