Add a limit to the length of a sequence of 'operator->' functions we will

follow when building a class member access expression. Based on a patch by
Rahul Jain!

llvm-svn: 194161

9 files changed, 96 insertions, 7 deletions

diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 4dc8bbfec10..e0a68384ad3 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1299,7 +1299,12 @@ Controlling implementation limits
 .. option:: -ftemplate-depth=N
 
   Sets the limit for recursively nested template instantiations to N.  The
-  default is 1024.
+  default is 256.
+
+.. option:: -foperator-arrow-depth=N
+
+  Sets the limit for iterative calls to 'operator->' functions to N.  The
+  default is 256.
 
 .. _objc:
 
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 6289d5a56b9..54b74debe70 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5144,6 +5144,16 @@ def err_capture_block_variable : Error<
 
 def err_operator_arrow_circular : Error<
   "circular pointer delegation detected">;
+def err_operator_arrow_depth_exceeded : Error<
+  "use of 'operator->' on type %0 would invoke a sequence of more than %1 "
+  "'operator->' calls">;
+def note_operator_arrow_here : Note<
+  "'operator->' declared here produces an object of type %0">;
+def note_operator_arrows_suppressed : Note<
+  "(skipping %0 'operator->'%s0 in backtrace)">;
+def note_operator_arrow_depth : Note<
+  "use -foperator-arrow-depth=N to increase 'operator->' limit">;
+
 def err_pseudo_dtor_base_not_scalar : Error<
   "object expression of non-scalar type %0 cannot be used in a "
   "pseudo-destructor expression">;
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 72b563dfe34..5a1025cba7e 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -161,6 +161,8 @@ ENUM_LANGOPT(StackProtector, StackProtectorMode, 2, SSPOff,
 ENUM_LANGOPT(SignedOverflowBehavior, SignedOverflowBehaviorTy, 2, SOB_Undefined,
              "signed integer overflow handling")
 
+BENIGN_LANGOPT(ArrowDepth, 32, 256,
+               "maximum number of operator->s to follow")
 BENIGN_LANGOPT(InstantiationDepth, 32, 256,
                "maximum template instantiation depth")
 BENIGN_LANGOPT(ConstexprCallDepth, 32, 512,
diff --git a/clang/include/clang/Driver/CC1Options.td b/clang/include/clang/Driver/CC1Options.td
index 6b7dac8e444..85cfdcf3946 100644
--- a/clang/include/clang/Driver/CC1Options.td
+++ b/clang/include/clang/Driver/CC1Options.td
@@ -442,6 +442,8 @@ def ftype_visibility : Separate<["-"], "ftype-visibility">,
   HelpText<"Default type visibility">;
 def ftemplate_depth : Separate<["-"], "ftemplate-depth">,
   HelpText<"Maximum depth of recursive template instantiation">;
+def foperator_arrow_depth : Separate<["-"], "foperator-arrow-depth">,
+  HelpText<"Maximum number of 'operator->'s to call for a member access">;
 def fconstexpr_depth : Separate<["-"], "fconstexpr-depth">,
   HelpText<"Maximum depth of recursive constexpr function calls">;
 def fconstexpr_steps : Separate<["-"], "fconstexpr-steps">,
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index cc2de9f914f..faaaee1e931 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -776,6 +776,8 @@ def ftemplate_depth_EQ : Joined<["-"], "ftemplate-depth=">, Group<f_Group>;
 def ftemplate_depth_ : Joined<["-"], "ftemplate-depth-">, Group<f_Group>;
 def ftemplate_backtrace_limit_EQ : Joined<["-"], "ftemplate-backtrace-limit=">,
                                    Group<f_Group>;
+def foperator_arrow_depth_EQ : Joined<["-"], "foperator-arrow-depth=">,
+                               Group<f_Group>;
 def ftest_coverage : Flag<["-"], "ftest-coverage">, Group<f_Group>;
 def fvectorize : Flag<["-"], "fvectorize">, Group<f_Group>,
   HelpText<"Enable the loop vectorization passes">;
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 5ac2268ee3e..7c987191d80 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2832,6 +2832,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(A->getValue());
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_foperator_arrow_depth_EQ)) {
+    CmdArgs.push_back("-foperator-arrow-depth");
+    CmdArgs.push_back(A->getValue());
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_fconstexpr_depth_EQ)) {
     CmdArgs.push_back("-fconstexpr-depth");
     CmdArgs.push_back(A->getValue());
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index d419d8a9eaf..c1999e84c44 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1322,6 +1322,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.MathErrno = !Opts.OpenCL && Args.hasArg(OPT_fmath_errno);
   Opts.InstantiationDepth =
       getLastArgIntValue(Args, OPT_ftemplate_depth, 256, Diags);
+  Opts.ArrowDepth =
+      getLastArgIntValue(Args, OPT_foperator_arrow_depth, 256, Diags);
   Opts.ConstexprCallDepth =
       getLastArgIntValue(Args, OPT_fconstexpr_depth, 512, Diags);
   Opts.ConstexprStepLimit =
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 6f72d6598eb..2e71270b4e8 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -5149,6 +5149,32 @@ ExprResult Sema::ActOnDecltypeExpression(Expr *E) {
   return Owned(E);
 }
 
+/// Note a set of 'operator->' functions that were used for a member access.
+static void noteOperatorArrows(Sema &S,
+                               llvm::ArrayRef<FunctionDecl *> OperatorArrows) {
+  unsigned SkipStart = OperatorArrows.size(), SkipCount = 0;
+  // FIXME: Make this configurable?
+  unsigned Limit = 9;
+  if (OperatorArrows.size() > Limit) {
+    // Produce Limit-1 normal notes and one 'skipping' note.
+    SkipStart = (Limit - 1) / 2 + (Limit - 1) % 2;
+    SkipCount = OperatorArrows.size() - (Limit - 1);
+  }
+
+  for (unsigned I = 0; I < OperatorArrows.size(); /**/) {
+    if (I == SkipStart) {
+      S.Diag(OperatorArrows[I]->getLocation(),
+             diag::note_operator_arrows_suppressed)
+          << SkipCount;
+      I += SkipCount;
+    } else {
+      S.Diag(OperatorArrows[I]->getLocation(), diag::note_operator_arrow_here)
+          << OperatorArrows[I]->getCallResultType();
+      ++I;
+    }
+  }
+}
+
 ExprResult
 Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base, SourceLocation OpLoc,
                                    tok::TokenKind OpKind, ParsedType &ObjectType,
@@ -5181,15 +5207,25 @@ Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base, SourceLocation OpLoc,
   //   [...] When operator->returns, the operator-> is applied  to the value
   //   returned, with the original second operand.
   if (OpKind == tok::arrow) {
+    QualType StartingType = BaseType;
     bool NoArrowOperatorFound = false;
     bool FirstIteration = true;
     FunctionDecl *CurFD = dyn_cast<FunctionDecl>(CurContext);
     // The set of types we've considered so far.
     llvm::SmallPtrSet<CanQualType,8> CTypes;
-    SmallVector<SourceLocation, 8> Locations;
+    SmallVector<FunctionDecl*, 8> OperatorArrows;
     CTypes.insert(Context.getCanonicalType(BaseType));
 
     while (BaseType->isRecordType()) {
+      if (OperatorArrows.size() >= getLangOpts().ArrowDepth) {
+        Diag(OpLoc, diag::err_operator_arrow_depth_exceeded)
+          << BaseType << getLangOpts().ArrowDepth << Base->getSourceRange();
+        noteOperatorArrows(*this, OperatorArrows);
+        Diag(OpLoc, diag::note_operator_arrow_depth)
+          << getLangOpts().ArrowDepth;
+        return ExprError();
+      }
+
       Result = BuildOverloadedArrowExpr(
           S, Base, OpLoc,
           // When in a template specialization and on the first loop iteration,
@@ -5203,7 +5239,7 @@ Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base, SourceLocation OpLoc,
         if (NoArrowOperatorFound) {
           if (FirstIteration) {
             Diag(OpLoc, diag::err_typecheck_member_reference_suggestion)
-              << BaseType << 1 << Base->getSourceRange()
+              << StartingType << 1 << Base->getSourceRange()
               << FixItHint::CreateReplacement(OpLoc, ".");
             OpKind = tok::period;
             break;
@@ -5220,13 +5256,12 @@ Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base, SourceLocation OpLoc,
       }
       Base = Result.get();
       if (CXXOperatorCallExpr *OpCall = dyn_cast<CXXOperatorCallExpr>(Base))
-        Locations.push_back(OpCall->getDirectCallee()->getLocation());
+        OperatorArrows.push_back(OpCall->getDirectCallee());
       BaseType = Base->getType();
       CanQualType CBaseType = Context.getCanonicalType(BaseType);
       if (!CTypes.insert(CBaseType)) {
-        Diag(OpLoc, diag::err_operator_arrow_circular);
-        for (unsigned i = 0; i < Locations.size(); i++)
-          Diag(Locations[i], diag::note_declared_at);
+        Diag(OpLoc, diag::err_operator_arrow_circular) << StartingType;
+        noteOperatorArrows(*this, OperatorArrows);
         return ExprError();
       }
       FirstIteration = false;
diff --git a/clang/test/SemaCXX/operator-arrow-depth.cpp b/clang/test/SemaCXX/operator-arrow-depth.cpp
new file mode 100644
index 00000000000..4e098823ae8
--- /dev/null
+++ b/clang/test/SemaCXX/operator-arrow-depth.cpp
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -DMAX=128 -foperator-arrow-depth 128
+// RUN: %clang_cc1 -fsyntax-only -verify %s -DMAX=2 -foperator-arrow-depth 2
+// RUN: %clang -fsyntax-only -Xclang -verify %s -DMAX=10 -foperator-arrow-depth=10
+
+template<int N> struct B;
+template<int N> struct A {
+  B<N> operator->(); // expected-note +{{'operator->' declared here produces an object of type 'B<}}
+};
+template<int N> struct B {
+  A<N-1> operator->(); // expected-note +{{'operator->' declared here produces an object of type 'A<}}
+#if MAX != 2
+  // expected-note-re@-2 {{(skipping (120|2) 'operator->'s in backtrace)}}
+#endif
+};
+
+struct X { int n; };
+template<> struct B<1> {
+  X *operator->();
+};
+
+A<MAX/2> good;
+int n = good->n;
+
+B<MAX/2 + 1> bad;
+int m = bad->n; // expected-error-re {{use of 'operator->' on type 'B<(1|5|64)>' would invoke a sequence of more than (2|10|128) 'operator->' calls}}
+                // expected-note@-1 {{use -foperator-arrow-depth=N to increase 'operator->' limit}}