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This results in expressions that appear in default function argument not
being checked for being actual constant expressions.
This aligns clang's behavior with the standard and fixes one of the
examples from https://wg21.link/P1073R3.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D145251
Files:
clang/lib/Sema/SemaExpr.cpp
clang/test/CXX/expr/expr.const/p6-2a.cpp
Index: clang/test/CXX/expr/expr.const/p6-2a.cpp
===================================================================
--- clang/test/CXX/expr/expr.const/p6-2a.cpp
+++ clang/test/CXX/expr/expr.const/p6-2a.cpp
@@ -43,14 +43,12 @@
constexpr Temporary t = {3}; // expected-error {{must have constant
destruction}} expected-note {{created here}} expected-note {{in call}}
namespace P1073R3 {
-consteval int f() { return 42; } // expected-note 3 {{declared here}}
+consteval int f() { return 42; } // expected-note 2 {{declared here}}
consteval auto g() { return f; }
-// FIXME: there should be no diagnostics associated with either h() or r.
-consteval int h(int (*p)() = g()) { return p(); } // expected-error {{call to
consteval function 'P1073R3::g' is not a constant expression}} \
- expected-note {{declared
here}} \
- expected-note {{pointer
to a consteval declaration is not a constant expression}}
-constexpr int r = h(); // expected-note {{in the default initalizer of 'p'}}
+consteval int h(int (*p)() = g()) { return p(); }
+constexpr int r = h();
constexpr auto e = g(); // expected-error {{call to consteval function
'P1073R3::g' is not a constant expression}} \
expected-error {{constexpr variable 'e' must be
initialized by a constant expression}} \
expected-note 2 {{pointer to a consteval
declaration is not a constant expression}}
+static_assert(r == 42);
} // namespace P1073R3
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -5918,7 +5918,10 @@
"default argument expression has capturing blocks?");
}
EnterExpressionEvaluationContext EvalContext(
- *this, ExpressionEvaluationContext::PotentiallyEvaluated, Param);
+ *this,
+ FD->isConsteval() ? ExpressionEvaluationContext::ImmediateFunctionContext
+ : ExpressionEvaluationContext::PotentiallyEvaluated,
+ Param);
ExprEvalContexts.back().IsCurrentlyCheckingDefaultArgumentOrInitializer =
SkipImmediateInvocations;
MarkDeclarationsReferencedInExpr(Init, /*SkipLocalVariables*/ true);
@@ -6006,7 +6009,11 @@
// If we are instantiating a template we won't have to
// retransform immediate calls.
EnterExpressionEvaluationContext EvalContext(
- *this, ExpressionEvaluationContext::PotentiallyEvaluated, Param);
+ *this,
+ FD->isConsteval()
+ ? ExpressionEvaluationContext::ImmediateFunctionContext
+ : ExpressionEvaluationContext::PotentiallyEvaluated,
+ Param);
if (Param->hasUninstantiatedDefaultArg()) {
if (InstantiateDefaultArgument(CallLoc, FD, Param))
Index: clang/test/CXX/expr/expr.const/p6-2a.cpp
===================================================================
--- clang/test/CXX/expr/expr.const/p6-2a.cpp
+++ clang/test/CXX/expr/expr.const/p6-2a.cpp
@@ -43,14 +43,12 @@
constexpr Temporary t = {3}; // expected-error {{must have constant destruction}} expected-note {{created here}} expected-note {{in call}}
namespace P1073R3 {
-consteval int f() { return 42; } // expected-note 3 {{declared here}}
+consteval int f() { return 42; } // expected-note 2 {{declared here}}
consteval auto g() { return f; }
-// FIXME: there should be no diagnostics associated with either h() or r.
-consteval int h(int (*p)() = g()) { return p(); } // expected-error {{call to consteval function 'P1073R3::g' is not a constant expression}} \
- expected-note {{declared here}} \
- expected-note {{pointer to a consteval declaration is not a constant expression}}
-constexpr int r = h(); // expected-note {{in the default initalizer of 'p'}}
+consteval int h(int (*p)() = g()) { return p(); }
+constexpr int r = h();
constexpr auto e = g(); // expected-error {{call to consteval function 'P1073R3::g' is not a constant expression}} \
expected-error {{constexpr variable 'e' must be initialized by a constant expression}} \
expected-note 2 {{pointer to a consteval declaration is not a constant expression}}
+static_assert(r == 42);
} // namespace P1073R3
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -5918,7 +5918,10 @@
"default argument expression has capturing blocks?");
}
EnterExpressionEvaluationContext EvalContext(
- *this, ExpressionEvaluationContext::PotentiallyEvaluated, Param);
+ *this,
+ FD->isConsteval() ? ExpressionEvaluationContext::ImmediateFunctionContext
+ : ExpressionEvaluationContext::PotentiallyEvaluated,
+ Param);
ExprEvalContexts.back().IsCurrentlyCheckingDefaultArgumentOrInitializer =
SkipImmediateInvocations;
MarkDeclarationsReferencedInExpr(Init, /*SkipLocalVariables*/ true);
@@ -6006,7 +6009,11 @@
// If we are instantiating a template we won't have to
// retransform immediate calls.
EnterExpressionEvaluationContext EvalContext(
- *this, ExpressionEvaluationContext::PotentiallyEvaluated, Param);
+ *this,
+ FD->isConsteval()
+ ? ExpressionEvaluationContext::ImmediateFunctionContext
+ : ExpressionEvaluationContext::PotentiallyEvaluated,
+ Param);
if (Param->hasUninstantiatedDefaultArg()) {
if (InstantiateDefaultArgument(CallLoc, FD, Param))
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