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[Diagnostics] Handle tautological left shifts in boolean context 

llvm-svn: 372749
This commit is contained in:
David Bolvansky 2019-09-24 13:14:18 +00:00
parent 355764e388
commit 275e4df115
3 changed files with 30 additions and 12 deletions
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4
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -6155,6 +6155,10 @@ def warn_integer_constants_in_conditional_always_true : Warning<
"converting the result of '?:' with integer constants to a boolean always "
"evaluates to 'true'">,
InGroup<TautologicalConstantCompare>;
def warn_left_shift_always : Warning<
"converting the result of '<<' to a boolean always evaluates "
"to %select{false|true}0">,
InGroup<TautologicalConstantCompare>;
def warn_comparison_of_mixed_enum_types : Warning<
"comparison of two values with different enumeration types"
"%diff{ ($ and $)|}0,1">,

19
clang/lib/Sema/SemaChecking.cpp
View File

@ -11314,17 +11314,26 @@ static void DiagnoseIntInBoolContext(Sema &S, Expr *E) {
if (const auto *BO = dyn_cast<BinaryOperator>(E)) {
BinaryOperator::Opcode Opc = BO->getOpcode();
Expr::EvalResult Result;
// Do not diagnose unsigned shifts.
if (Opc == BO_Shl && E->getType()->isSignedIntegerType())
S.Diag(ExprLoc, diag::warn_left_shift_in_bool_context) << E;
if (Opc == BO_Shl) {
const auto *LHS = getIntegerLiteral(BO->getLHS());
const auto *RHS = getIntegerLiteral(BO->getRHS());
if (LHS && LHS->getValue() == 0)
S.Diag(ExprLoc, diag::warn_left_shift_always) << 0;
else if (RHS && RHS->getValue().isNonNegative() &&
E->EvaluateAsInt(Result, S.Context, Expr::SE_AllowSideEffects))
S.Diag(ExprLoc, diag::warn_left_shift_always)
<< (Result.Val.getInt() != 0);
else if (E->getType()->isSignedIntegerType())
S.Diag(ExprLoc, diag::warn_left_shift_in_bool_context) << E;
}
}
if (const auto *CO = dyn_cast<ConditionalOperator>(E)) {
const auto *LHS = getIntegerLiteral(CO->getTrueExpr());
if (!LHS)
return;
const auto *RHS = getIntegerLiteral(CO->getFalseExpr());
if (!RHS)
if (!LHS || !RHS)
return;
if ((LHS->getValue() == 0 || LHS->getValue() == 1) &&
(RHS->getValue() == 0 || RHS->getValue() == 1))

19
clang/test/Sema/warn-int-in-bool-context.c
View File

@ -24,12 +24,17 @@ enum num {
int test(int a, unsigned b, enum num n) {
boolean r;
r = a << a; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(a << a) != 0'?}}
r = MM; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(a << a) != 0'?}}
r = (1 << 7); // expected-warning {{converting the result of '<<' to a boolean; did you mean '(1 << 7) != 0'?}}
r = 2UL << 2;
r = 2 << b; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(2 << b) != 0'?}}
r = (unsigned)(2 << b);
r = a << a; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(a << a) != 0'?}}
r = MM; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(a << a) != 0'?}}
r = (1 << 7); // expected-warning {{converting the result of '<<' to a boolean always evaluates to true}}
r = 2UL << 2; // expected-warning {{converting the result of '<<' to a boolean always evaluates to true}}
r = 0 << a; // expected-warning {{converting the result of '<<' to a boolean always evaluates to false}}
r = 0 << 2; // expected-warning {{converting the result of '<<' to a boolean always evaluates to false}}
r = 1 << 0; // expected-warning {{converting the result of '<<' to a boolean always evaluates to true}}
r = 1 << 2; // expected-warning {{converting the result of '<<' to a boolean always evaluates to true}}
r = 1ULL << 2; // expected-warning {{converting the result of '<<' to a boolean always evaluates to true}}
r = 2 << b; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(2 << b) != 0'?}}
r = (unsigned)(2 << b);
r = b << 7;
r = (1 << a); // expected-warning {{converting the result of '<<' to a boolean; did you mean '(1 << a) != 0'?}}
r = TWO << a; // expected-warning {{converting the result of '<<' to a boolean; did you mean '(2 << a) != 0'?}}
@ -39,7 +44,7 @@ int test(int a, unsigned b, enum num n) {
return a;
for (a = 0; 1 << a; a++) // expected-warning {{converting the result of '<<' to a boolean; did you mean '(1 << a) != 0'?}}
;
;
if (a << TWO) // expected-warning {{converting the result of '<<' to a boolean; did you mean '(a << 2) != 0'?}}
return a;