cor3ntin created this revision.
cor3ntin requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Support Narrowing conversions to bool in if constexpr condition
under C++23 language mode.
Only if constexpr is implemented as the behavior of static_assert
is already conforming.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D105127
Files:
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaExprCXX.cpp
clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
clang/www/cxx_status.html
Index: clang/www/cxx_status.html
===================================================================
--- clang/www/cxx_status.html
+++ clang/www/cxx_status.html
@@ -1296,7 +1296,7 @@
<tr>
<td>Narrowing contextual conversions to bool</td>
<td><a href="https://wg21.link/P1401R5";>P1401R5</a></td>
- <td class="none" align="center">No</td>
+ <td class="full" align="center">Clang 13</td>
</tr>
<tr>
<td>Trimming whitespaces before line splicing</td>
Index: clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
===================================================================
--- clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
+++ clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
@@ -1,5 +1,7 @@
// RUN: %clang_cc1 -std=c++1z -verify %s
// RUN: %clang_cc1 -std=c++1z -verify %s -DUNDEFINED
+// RUN: %clang_cc1 -std=c++2b -verify %s
+// RUN: %clang_cc1 -std=c++2b -verify %s -DUNDEFINED
#ifdef UNDEFINED
// "used but not defined" errors don't get produced if we have more interesting
@@ -40,17 +42,41 @@
namespace ccce {
void f() {
if (5) {}
- if constexpr (5) {} // expected-error {{cannot be narrowed}}
+ if constexpr (5) {
+ }
}
template<int N> void g() {
- if constexpr (N) {} // expected-error {{cannot be narrowed}}
+ if constexpr (N) {
+ }
}
- template void g<5>(); // expected-note {{instantiation of}}
+ template void g<5>();
void h() {
- if constexpr (4.3) {} // expected-error{{conversion from 'double' to 'bool' is not allowed in a converted constant expression}}
+ if constexpr (4.3) {
+ }
constexpr void *p = nullptr;
- if constexpr (p) {} // expected-error{{conversion from 'void *const' to 'bool' is not allowed in a converted constant expression}}
+ if constexpr (p) {
+ }
}
+
+ void not_constant(int b) {
+ if constexpr (bool(b)) {
+ } // expected-error {{constexpr if condition is not a constant expression}}
+ if constexpr (b) {
+ } // expected-error {{constexpr if condition is not a constant expression}}
+ }
+
+#if __cplusplus <= 202002
+ // expected-error@45 {{cannot be narrowed}}
+ // expected-error@48 {{cannot be narrowed}}
+ // expected-note@50 {{instantiation of}}
+ // expected-error@52 {{conversion from 'double' to 'bool' is not allowed in a converted constant expression}}
+ // expected-error@54 {{conversion from 'void *const' to 'bool' is not allowed in a converted constant expression}}
+#else
+ // expected-warning@52 {{implicit conversion from 'double' to 'bool' changes value}}
+#endif
+ // expected-note@58 {{cannot be used in a constant expression}}
+ // expected-note@59 {{cannot be used in a constant expression}}
+ // expected-note@57 2{{declared here}}
}
namespace generic_lambda {
Index: clang/lib/Sema/SemaExprCXX.cpp
===================================================================
--- clang/lib/Sema/SemaExprCXX.cpp
+++ clang/lib/Sema/SemaExprCXX.cpp
@@ -3920,11 +3920,21 @@
// expression, implicitly converted to bool.
//
// FIXME: Return this value to the caller so they don't need to recompute it.
- llvm::APSInt Value(/*BitWidth*/1);
- return (IsConstexpr && !CondExpr->isValueDependent())
- ? CheckConvertedConstantExpression(CondExpr, Context.BoolTy, Value,
- CCEK_ConstexprIf)
- : PerformContextuallyConvertToBool(CondExpr);
+
+ if ((IsConstexpr && !LangOpts.CPlusPlus2b) && !CondExpr->isValueDependent()) {
+ llvm::APSInt Value(/*BitWidth*/ 1);
+ return CheckConvertedConstantExpression(CondExpr, Context.BoolTy, Value,
+ CCEK_ConstexprIf);
+ }
+ ExprResult E = PerformContextuallyConvertToBool(CondExpr);
+ if (!IsConstexpr || CondExpr->isValueDependent())
+ return E;
+
+ llvm::APSInt Cond;
+ E = VerifyIntegerConstantExpression(
+ E.get(), &Cond,
+ diag::err_constexpr_if_condition_expression_is_not_constant);
+ return E;
}
/// Helper function to determine whether this is the (deprecated) C++
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1487,6 +1487,8 @@
// C++ declarations
def err_static_assert_expression_is_not_constant : Error<
"static_assert expression is not an integral constant expression">;
+def err_constexpr_if_condition_expression_is_not_constant : Error<
+ "constexpr if condition is not a constant expression convertible to bool">;
def err_static_assert_failed : Error<"static_assert failed%select{ %1|}0">;
def err_static_assert_requirement_failed : Error<
"static_assert failed due to requirement '%0'%select{ %2|}1">;
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
