[Clang][WIP] Increase the default expression nesting limit.

Fixes #94728

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -169,6 +169,8 @@ Modified Compiler Flags
   the behavior of ``-mtp`` in gcc. This changes the default behavior for ARM targets that provide the ``TPIDRURO`` register as this will be used instead of a call to the ``__aeabi_read_tp``.
   Programs that use ``__aeabi_read_tp`` but do not use the ``TPIDRURO`` register must use ``-mtp=soft``. Fixes #123864
 
+- The compiler flag `-fbracket-depth` default value is increased from 256 to 2048. (#GH94728)
+
 Removed Compiler Flags
 -------------------------
 
@@ -264,7 +266,7 @@ Improvements to Clang's diagnostics
   as function arguments or return value respectively. Note that
   :doc:`ThreadSafetyAnalysis` still does not perform alias analysis. The
   feature will be default-enabled with ``-Wthread-safety`` in a future release.
-- The ``-Wsign-compare`` warning now treats expressions with bitwise not(~) and minus(-) as signed integers 
+- The ``-Wsign-compare`` warning now treats expressions with bitwise not(~) and minus(-) as signed integers
   except for the case where the operand is an unsigned integer
   and throws warning if they are compared with unsigned integers (##18878).
 - The ``-Wunnecessary-virtual-specifier`` warning has been added to warn about

clang/include/clang/Driver/Options.td

@@ -8161,7 +8161,7 @@ def fapply_global_visibility_to_externs : Flag<["-"], "fapply-global-visibility-
   MarshallingInfoFlag<LangOpts<"SetVisibilityForExternDecls">>;
 def fbracket_depth : Separate<["-"], "fbracket-depth">,
   HelpText<"Maximum nesting level for parentheses, brackets, and braces">,
-  MarshallingInfoInt<LangOpts<"BracketDepth">, "256">;
+  MarshallingInfoInt<LangOpts<"BracketDepth">, "2048">;
 defm const_strings : BoolOption<"f", "const-strings",
   LangOpts<"ConstStrings">, DefaultFalse,
   PosFlag<SetTrue, [], [ClangOption, CC1Option], "Use">,

clang/include/clang/Parse/Parser.h

@@ -91,6 +91,8 @@ class Parser : public CodeCompletionHandler {
 
   DiagnosticsEngine &Diags;
 
+  StackExhaustionHandler StackHandler;
+
   /// ScopeCache - Cache scopes to reduce malloc traffic.
   enum { ScopeCacheSize = 16 };
   unsigned NumCachedScopes;
@@ -518,7 +520,7 @@ class Parser : public CodeCompletionHandler {
   typedef Sema::FullExprArg FullExprArg;
 
   /// A SmallVector of statements.
-  typedef SmallVector<Stmt *, 32> StmtVector;
+  typedef SmallVector<Stmt *, 24> StmtVector;
 
   // Parsing methods.
 

clang/lib/Parse/ParseStmt.cpp

@@ -126,18 +126,19 @@ Parser::ParseStatementOrDeclaration(StmtVector &Stmts,
       Stmts, StmtCtx, TrailingElseLoc, CXX11Attrs, GNUOrMSAttrs);
   MaybeDestroyTemplateIds();
 
-  // Attributes that are left should all go on the statement, so concatenate the
-  // two lists.
-  ParsedAttributes Attrs(AttrFactory);
-  takeAndConcatenateAttrs(CXX11Attrs, GNUOrMSAttrs, Attrs);
+  CXX11Attrs.takeAllFrom(GNUOrMSAttrs);
+  if (!CXX11Attrs.Range.getBegin().isValid())
+    CXX11Attrs.Range.setBegin(GNUOrMSAttrs.Range.getBegin());
+  if (GNUOrMSAttrs.Range.getEnd().isValid())
+    CXX11Attrs.Range.setEnd(GNUOrMSAttrs.Range.getEnd());
 
-  assert((Attrs.empty() || Res.isInvalid() || Res.isUsable()) &&
+  assert((CXX11Attrs.empty() || Res.isInvalid() || Res.isUsable()) &&
          "attributes on empty statement");
 
-  if (Attrs.empty() || Res.isInvalid())
+  if (CXX11Attrs.empty() || Res.isInvalid())
     return Res;
 
-  return Actions.ActOnAttributedStmt(Attrs, Res.get());
+  return Actions.ActOnAttributedStmt(CXX11Attrs, Res.get());
 }
 
 namespace {
@@ -1057,7 +1058,11 @@ StmtResult Parser::ParseCompoundStatement(bool isStmtExpr,
   ParseScope CompoundScope(this, ScopeFlags);
 
   // Parse the statements in the body.
-  return ParseCompoundStatementBody(isStmtExpr);
+  StmtResult R;
+  StackHandler.runWithSufficientStackSpace(Tok.getLocation(), [&, this]() {
+    R = ParseCompoundStatementBody(isStmtExpr);
+  });
+  return R;
 }
 
 /// Parse any pragmas at the start of the compound expression. We handle these
@@ -1222,7 +1227,7 @@ StmtResult Parser::ParseCompoundStatementBody(bool isStmtExpr) {
   while (Tok.is(tok::kw___label__)) {
     SourceLocation LabelLoc = ConsumeToken();
 
-    SmallVector<Decl *, 8> DeclsInGroup;
+    SmallVector<Decl *, 4> DeclsInGroup;
     while (true) {
       if (Tok.isNot(tok::identifier)) {
         Diag(Tok, diag::err_expected) << tok::identifier;

clang/lib/Parse/Parser.cpp

@@ -17,6 +17,7 @@
 #include "clang/AST/DeclTemplate.h"
 #include "clang/Basic/DiagnosticParse.h"
 #include "clang/Basic/FileManager.h"
+#include "clang/Basic/StackExhaustionHandler.h"
 #include "clang/Parse/RAIIObjectsForParser.h"
 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/EnterExpressionEvaluationContext.h"
@@ -54,9 +55,10 @@ IdentifierInfo *Parser::getSEHExceptKeyword() {
 
 Parser::Parser(Preprocessor &pp, Sema &actions, bool skipFunctionBodies)
     : PP(pp), PreferredType(pp.isCodeCompletionEnabled()), Actions(actions),
-      Diags(PP.getDiagnostics()), GreaterThanIsOperator(true),
-      ColonIsSacred(false), InMessageExpression(false),
-      TemplateParameterDepth(0), ParsingInObjCContainer(false) {
+      Diags(PP.getDiagnostics()), StackHandler(Diags),
+      GreaterThanIsOperator(true), ColonIsSacred(false),
+      InMessageExpression(false), TemplateParameterDepth(0),
+      ParsingInObjCContainer(false) {
   SkipFunctionBodies = pp.isCodeCompletionEnabled() || skipFunctionBodies;
   Tok.startToken();
   Tok.setKind(tok::eof);

clang/test/Parser/parser_overflow.c

@@ -1,5 +1,5 @@
 // RUN: not %clang_cc1 %s -fsyntax-only -DHUGE 2>&1 | FileCheck %s
-// RUN: not %clang_cc1 %s -fsyntax-only 2>&1 | FileCheck %s
+// RUN: %clang_cc1 %s -fsyntax-only
 // RUN: not %clang_cc1 %s -fsyntax-only -fbracket-depth 299 2>&1 | FileCheck %s
 // RUN: %clang_cc1 %s -fsyntax-only -fbracket-depth 300
 // RUN: not %clang %s -fsyntax-only -fbracket-depth=299 2>&1 | FileCheck %s
@@ -15,5 +15,5 @@ void foo(void) {
 #endif
 }
 
-// CHECK: fatal error: bracket nesting level exceeded maximum of {{256|299}}
+// CHECK: fatal error: bracket nesting level exceeded maximum of {{2048|299}}
 // CHECK: note: use -fbracket-depth=N to increase maximum nesting level