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Add explanatory comments for ICE checking in C99 mode. 

llvm-svn: 142866
This commit is contained in:
Richard Smith 2011-10-24 22:35:48 +00:00
parent 43edb32f1f
commit 62f6595122
1 changed files with 10 additions and 1 deletions
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11
clang/lib/AST/ExprConstant.cpp
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@ -2974,6 +2974,9 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
return NoDiag();
case Expr::CallExprClass:
case Expr::CXXOperatorCallExprClass: {
// C99 6.6/3 allows function calls within unevaluated subexpressions of
// constant expressions, but they can never be ICEs because an ICE cannot
// contain an operand of (pointer to) function type.
const CallExpr *CE = cast<CallExpr>(E);
if (CE->isBuiltinCall(Ctx))
return CheckEvalInICE(E, Ctx);
@ -3034,6 +3037,9 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
case UO_PreDec:
case UO_AddrOf:
case UO_Deref:
// C99 6.6/3 allows increment and decrement within unevaluated
// subexpressions of constant expressions, but they can never be ICEs
// because an ICE cannot contain an lvalue operand.
return ICEDiag(2, E->getLocStart());
case UO_Extension:
case UO_LNot:
@ -3050,7 +3056,7 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
case Expr::OffsetOfExprClass: {
// Note that per C99, offsetof must be an ICE. And AFAIK, using
// Evaluate matches the proposed gcc behavior for cases like
// "offsetof(struct s{int x[4];}, x[!.0])". This doesn't affect
// "offsetof(struct s{int x[4];}, x[1.0])". This doesn't affect
// compliance: we should warn earlier for offsetof expressions with
// array subscripts that aren't ICEs, and if the array subscripts
// are ICEs, the value of the offsetof must be an integer constant.
@ -3079,6 +3085,9 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
case BO_AndAssign:
case BO_XorAssign:
case BO_OrAssign:
// C99 6.6/3 allows assignments within unevaluated subexpressions of
// constant expressions, but they can never be ICEs because an ICE cannot
// contain an lvalue operand.
return ICEDiag(2, E->getLocStart());
case BO_Mul: