C++1y: Add a step limit to constexpr evaluation, to catch runaway loops.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181388 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 1460267..08c26a3 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -380,6 +380,11 @@
/// NextCallIndex - The next call index to assign.
unsigned NextCallIndex;
+ /// StepsLeft - The remaining number of evaluation steps we're permitted
+ /// to perform. This is essentially a limit for the number of statements
+ /// we will evaluate.
+ unsigned StepsLeft;
+
/// BottomFrame - The frame in which evaluation started. This must be
/// initialized after CurrentCall and CallStackDepth.
CallStackFrame BottomFrame;
@@ -404,9 +409,10 @@
bool IntOverflowCheckMode;
EvalInfo(const ASTContext &C, Expr::EvalStatus &S,
- bool OverflowCheckMode=false)
+ bool OverflowCheckMode = false)
: Ctx(const_cast<ASTContext&>(C)), EvalStatus(S), CurrentCall(0),
CallStackDepth(0), NextCallIndex(1),
+ StepsLeft(getLangOpts().ConstexprStepLimit),
BottomFrame(*this, SourceLocation(), 0, 0, 0),
EvaluatingDecl(0), EvaluatingDeclValue(0), HasActiveDiagnostic(false),
CheckingPotentialConstantExpression(false),
@@ -446,6 +452,15 @@
return (Frame->Index == CallIndex) ? Frame : 0;
}
+ bool nextStep(const Stmt *S) {
+ if (!StepsLeft) {
+ Diag(S->getLocStart(), diag::note_constexpr_step_limit_exceeded);
+ return false;
+ }
+ --StepsLeft;
+ return true;
+ }
+
private:
/// Add a diagnostic to the diagnostics list.
PartialDiagnostic &addDiag(SourceLocation Loc, diag::kind DiagId) {
@@ -530,9 +545,9 @@
bool keepEvaluatingAfterFailure() {
// Should return true in IntOverflowCheckMode, so that we check for
// overflow even if some subexpressions can't be evaluated as constants.
- return IntOverflowCheckMode ||
- (CheckingPotentialConstantExpression &&
- EvalStatus.Diag && EvalStatus.Diag->empty());
+ return StepsLeft && (IntOverflowCheckMode ||
+ (CheckingPotentialConstantExpression &&
+ EvalStatus.Diag && EvalStatus.Diag->empty()));
}
};
@@ -2794,6 +2809,9 @@
// Evaluate a statement.
static EvalStmtResult EvaluateStmt(APValue &Result, EvalInfo &Info,
const Stmt *S) {
+ if (!Info.nextStep(S))
+ return ESR_Failed;
+
// FIXME: Mark all temporaries in the current frame as destroyed at
// the end of each full-expression.
switch (S->getStmtClass()) {
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 47d12e1..a86199e 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2667,6 +2667,11 @@
CmdArgs.push_back(A->getValue());
}
+ if (Arg *A = Args.getLastArg(options::OPT_fconstexpr_steps_EQ)) {
+ CmdArgs.push_back("-fconstexpr-steps");
+ CmdArgs.push_back(A->getValue());
+ }
+
if (Arg *A = Args.getLastArg(options::OPT_fbracket_depth_EQ)) {
CmdArgs.push_back("-fbracket-depth");
CmdArgs.push_back(A->getValue());
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 42ea96f..9c8eea1 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1251,6 +1251,8 @@
Diags);
Opts.ConstexprCallDepth = Args.getLastArgIntValue(OPT_fconstexpr_depth, 512,
Diags);
+ Opts.ConstexprStepLimit = Args.getLastArgIntValue(OPT_fconstexpr_steps,
+ 1048576, Diags);
Opts.BracketDepth = Args.getLastArgIntValue(OPT_fbracket_depth, 256, Diags);
Opts.DelayedTemplateParsing = Args.hasArg(OPT_fdelayed_template_parsing);
Opts.NumLargeByValueCopy = Args.getLastArgIntValue(OPT_Wlarge_by_value_copy_EQ,