r343064 - P0859R0: List-initialization is potentially-constant-evaluated and
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Tue Sep 25 21:36:56 PDT 2018
Author: rsmith
Date: Tue Sep 25 21:36:55 2018
New Revision: 343064
URL: http://llvm.org/viewvc/llvm-project?rev=343064&view=rev
Log:
P0859R0: List-initialization is potentially-constant-evaluated and
triggers instantiation of constexpr functions.
We mostly implemented this since Clang 6, but missed the template
instantiation case.
We do not implement the '&cast-expression' special case. It appears to
be a mistake / oversight. I've mailed CWG to see if we can remove it.
Added:
cfe/trunk/test/CXX/expr/expr.const/p6.cpp
cfe/trunk/test/CXX/temp/temp.spec/temp.inst/p7.cpp
Modified:
cfe/trunk/lib/Sema/TreeTransform.h
cfe/trunk/www/cxx_status.html
Modified: cfe/trunk/lib/Sema/TreeTransform.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/TreeTransform.h?rev=343064&r1=343063&r2=343064&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/TreeTransform.h (original)
+++ cfe/trunk/lib/Sema/TreeTransform.h Tue Sep 25 21:36:55 2018
@@ -3386,6 +3386,11 @@ ExprResult TreeTransform<Derived>::Trans
if (Construct && Construct->isStdInitListInitialization())
return TransformInitializer(Construct->getArg(0), NotCopyInit);
+ // Enter a list-init context if this was list initialization.
+ EnterExpressionEvaluationContext Context(
+ getSema(), EnterExpressionEvaluationContext::InitList,
+ Construct->isListInitialization());
+
SmallVector<Expr*, 8> NewArgs;
bool ArgChanged = false;
if (getDerived().TransformExprs(Construct->getArgs(), Construct->getNumArgs(),
@@ -9549,6 +9554,9 @@ TreeTransform<Derived>::TransformInitLis
bool InitChanged = false;
+ EnterExpressionEvaluationContext Context(
+ getSema(), EnterExpressionEvaluationContext::InitList);
+
SmallVector<Expr*, 4> Inits;
if (getDerived().TransformExprs(E->getInits(), E->getNumInits(), false,
Inits, &InitChanged))
@@ -10780,9 +10788,14 @@ TreeTransform<Derived>::TransformCXXCons
bool ArgumentChanged = false;
SmallVector<Expr*, 8> Args;
- if (getDerived().TransformExprs(E->getArgs(), E->getNumArgs(), true, Args,
- &ArgumentChanged))
- return ExprError();
+ {
+ EnterExpressionEvaluationContext Context(
+ getSema(), EnterExpressionEvaluationContext::InitList,
+ E->isListInitialization());
+ if (getDerived().TransformExprs(E->getArgs(), E->getNumArgs(), true, Args,
+ &ArgumentChanged))
+ return ExprError();
+ }
if (!getDerived().AlwaysRebuild() &&
T == E->getType() &&
@@ -10865,9 +10878,14 @@ TreeTransform<Derived>::TransformCXXTemp
bool ArgumentChanged = false;
SmallVector<Expr*, 8> Args;
Args.reserve(E->getNumArgs());
- if (TransformExprs(E->getArgs(), E->getNumArgs(), true, Args,
- &ArgumentChanged))
- return ExprError();
+ {
+ EnterExpressionEvaluationContext Context(
+ getSema(), EnterExpressionEvaluationContext::InitList,
+ E->isListInitialization());
+ if (TransformExprs(E->getArgs(), E->getNumArgs(), true, Args,
+ &ArgumentChanged))
+ return ExprError();
+ }
if (!getDerived().AlwaysRebuild() &&
T == E->getTypeSourceInfo() &&
@@ -11159,9 +11177,14 @@ TreeTransform<Derived>::TransformCXXUnre
bool ArgumentChanged = false;
SmallVector<Expr*, 8> Args;
Args.reserve(E->arg_size());
- if (getDerived().TransformExprs(E->arg_begin(), E->arg_size(), true, Args,
- &ArgumentChanged))
- return ExprError();
+ {
+ EnterExpressionEvaluationContext Context(
+ getSema(), EnterExpressionEvaluationContext::InitList,
+ E->isListInitialization());
+ if (getDerived().TransformExprs(E->arg_begin(), E->arg_size(), true, Args,
+ &ArgumentChanged))
+ return ExprError();
+ }
if (!getDerived().AlwaysRebuild() &&
T == E->getTypeSourceInfo() &&
Added: cfe/trunk/test/CXX/expr/expr.const/p6.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/expr/expr.const/p6.cpp?rev=343064&view=auto
==============================================================================
--- cfe/trunk/test/CXX/expr/expr.const/p6.cpp (added)
+++ cfe/trunk/test/CXX/expr/expr.const/p6.cpp Tue Sep 25 21:36:55 2018
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -std=c++17 -verify %s
+
+template<typename T> int not_constexpr() { return T::error; }
+template<typename T> constexpr int is_constexpr() { return T::error; } // expected-error {{'::'}}
+
+template<typename T> int not_constexpr_var = T::error;
+template<typename T> constexpr int is_constexpr_var = T::error; // expected-error {{'::'}}
+template<typename T> const int is_const_var = T::error; // expected-error {{'::'}}
+template<typename T> const volatile int is_const_volatile_var = T::error;
+template<typename T> T is_dependent_var = T::error; // expected-error {{'::'}}
+template<typename T> int &is_reference_var = T::error; // expected-error {{'::'}}
+template<typename T> float is_float_var = T::error;
+
+void test() {
+ // Do not instantiate functions referenced in unevaluated operands...
+ (void)sizeof(not_constexpr<long>());
+ (void)sizeof(is_constexpr<long>());
+ (void)sizeof(not_constexpr_var<long>);
+ (void)sizeof(is_constexpr_var<long>);
+ (void)sizeof(is_const_var<long>);
+ (void)sizeof(is_const_volatile_var<long>);
+ (void)sizeof(is_dependent_var<long>);
+ (void)sizeof(is_dependent_var<const long>);
+ (void)sizeof(is_reference_var<long>);
+ (void)sizeof(is_float_var<long>);
+
+ // ... but do if they are potentially constant evaluated, and refer to
+ // constexpr functions or to variables usable in constant expressions.
+ (void)sizeof(int{not_constexpr<int>()});
+ (void)sizeof(int{is_constexpr<int>()}); // expected-note {{instantiation of}}
+ (void)sizeof(int{not_constexpr_var<int>});
+ (void)sizeof(int{is_constexpr_var<int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_const_var<int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_const_volatile_var<int>});
+ (void)sizeof(int{is_dependent_var<int>});
+ (void)sizeof(int{is_dependent_var<const int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_reference_var<int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_float_var<int>}); // expected-error {{cannot be narrowed}} expected-note {{cast}}
+}
Added: cfe/trunk/test/CXX/temp/temp.spec/temp.inst/p7.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/temp/temp.spec/temp.inst/p7.cpp?rev=343064&view=auto
==============================================================================
--- cfe/trunk/test/CXX/temp/temp.spec/temp.inst/p7.cpp (added)
+++ cfe/trunk/test/CXX/temp/temp.spec/temp.inst/p7.cpp Tue Sep 25 21:36:55 2018
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -verify -std=c++17 %s
+
+template<typename T> constexpr int f() { return T::value; } // expected-error {{'::'}}
+template<bool B, typename T> void g(decltype(B ? f<T>() : 0));
+template<bool B, typename T> void g(...);
+template<bool B, typename T> void h(decltype(int{B ? f<T>() : 0})); // expected-note {{instantiation of}}
+template<bool B, typename T> void h(...);
+void x() {
+ g<false, int>(0); // ok
+ g<true, int>(0); // ok
+ h<false, int>(0); // expected-note {{while substituting}}
+}
Modified: cfe/trunk/www/cxx_status.html
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/www/cxx_status.html?rev=343064&r1=343063&r2=343064&view=diff
==============================================================================
--- cfe/trunk/www/cxx_status.html (original)
+++ cfe/trunk/www/cxx_status.html Tue Sep 25 21:36:55 2018
@@ -207,7 +207,7 @@ with <a href="http://libcxx.llvm.org/">l
<tr>
<!-- from Albuquerque 2017 -->
<td><a href="http://wg21.link/p0859r0">P0859R0</a> (<a href="#dr">DR</a>)</td>
- <td class="none" align="center">No</td>
+ <td class="svn" align="center">SVN</td>
</tr>
<tr>
<td>Alignment support</td>
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