[clang] Add tests for some CWG issues from 2024-05-31 telecon #94167

Endilll · 2024-06-02T19:17:13Z

This patch adds tests for some CWG issues that were discussed at 2024-05-31 telecon. While all of them are tentatively ready at the moment, I'm expecting them to be moved to DRs without changes. CWG issues that are expected to have follow-ups are not included in this PR.

I also realized that cwg28xx.cpp has been testing without -pedantic-errors. I fixed that. Fortunately, no existing tests had anything hidden by the lack of this flag.

The following CWG issues are covered:
CWG2877 "Type-only lookup for using-enum-declarator"
CWG2882 "Unclear treatment of conversion to void"
CWG2883 "Definition of "odr-usable" ignores lambda scopes"
CWG2885 "Non-eligible trivial default constructors"
CWG2886 "Temporaries and trivial potentially-throwing special member functions"

llvmbot · 2024-06-02T19:17:42Z

@llvm/pr-subscribers-clang

Author: Vlad Serebrennikov (Endilll)

Changes

This patch adds tests for some CWG issues that were discussed at 2024-05-31 telecon. While all of them are tentatively ready at the moment, I'm expecting them to be moved to DRs without changes. CWG issues that are expected to have follow-ups are not included in this PR.

The following CWG issues are covered:
CWG2877 "Type-only lookup for using-enum-declarator"
CWG2882 "Unclear treatment of conversion to void"
CWG2883 "Definition of "odr-usable" ignores lambda scopes"
CWG2885 "Non-eligible trivial default constructors"
CWG2886 "Temporaries and trivial potentially-throwing special member functions"

Full diff: https://github.com/llvm/llvm-project/pull/94167.diff

2 Files Affected:

(modified) clang/test/CXX/drs/cwg28xx.cpp (+88-7)
(modified) clang/www/cxx_dr_status.html (+5-5)

diff --git a/clang/test/CXX/drs/cwg28xx.cpp b/clang/test/CXX/drs/cwg28xx.cpp
index 8469a065ccaa0..da81eccc8dc22 100644
--- a/clang/test/CXX/drs/cwg28xx.cpp
+++ b/clang/test/CXX/drs/cwg28xx.cpp
@@ -1,10 +1,10 @@
-// RUN: %clang_cc1 -std=c++98 -verify=expected %s
-// RUN: %clang_cc1 -std=c++11 -verify=expected %s
-// RUN: %clang_cc1 -std=c++14 -verify=expected %s
-// RUN: %clang_cc1 -std=c++17 -verify=expected %s
-// RUN: %clang_cc1 -std=c++20 -verify=expected,since-cxx20 %s
-// RUN: %clang_cc1 -std=c++23 -verify=expected,since-cxx20,since-cxx23 %s
-// RUN: %clang_cc1 -std=c++2c -verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
+// RUN: %clang_cc1 -std=c++98 -pedantic-errors -verify=expected,cxx98 %s
+// RUN: %clang_cc1 -std=c++11 -pedantic-errors -verify=expected %s
+// RUN: %clang_cc1 -std=c++14 -pedantic-errors -verify=expected %s
+// RUN: %clang_cc1 -std=c++17 -pedantic-errors -verify=expected %s
+// RUN: %clang_cc1 -std=c++20 -pedantic-errors -verify=expected,since-cxx20 %s
+// RUN: %clang_cc1 -std=c++23 -pedantic-errors -verify=expected,since-cxx20,since-cxx23 %s
+// RUN: %clang_cc1 -std=c++2c -pedantic-errors -verify=expected,since-cxx20,since-cxx23,since-cxx26 %s
 
 namespace cwg2819 { // cwg2819: 19 tentatively ready 2023-12-01
 #if __cpp_constexpr >= 202306L
@@ -110,6 +110,26 @@ struct A {
 
 } // namespace cwg2858
 
+namespace cwg2877 { // cwg2877: no tentatively ready 2024-05-31
+#if __cplusplus >= 202002L
+enum E { x };
+void f() {
+  int E;
+  // FIXME: OK, names ::E
+  using enum E;
+  // since-cxx20-error@-1 {{unknown type name E}}
+}
+using F = E;
+using enum F;     // OK, designates ::E
+template<class T> using EE = T;
+void g() {
+  // FIXME: OK, designates ::E
+  using enum EE<E>;
+  // since-cxx20-error@-1 {{using enum requires an enum or typedef name}}
+}
+#endif
+} // namespace cwg2877
+
 namespace cwg2881 { // cwg2881: 19 tentatively ready 2024-04-19
 
 #if __cplusplus >= 202302L
@@ -180,3 +200,64 @@ void f() {
 
 } // namespace cwg2881
 
+namespace cwg2882 { // cwg2882: 2.7 tentatively ready 2024-05-31
+struct C {
+  operator void() = delete;
+  // expected-warning@-1 {{conversion function converting 'cwg2882::C' to 'void' will never be used}}
+  // cxx98-error@-2 {{deleted function definitions are a C++11 extension}}
+};
+
+void f(C c) {
+  (void)c;
+}
+} // namespace cwg2882
+
+namespace cwg2883 { // cwg2883: no tentatively ready 2024-05-31
+#if __cplusplus >= 201103L
+void f() {
+  int x;
+  (void)[&] {
+    return x;
+  };
+}
+#endif
+#if __cplusplus >= 202002L
+struct A {
+  A() = default;
+  A(const A &) = delete; // #cwg2883-A-copy-ctor
+  constexpr operator int() { return 42; }
+};
+void g() {
+  constexpr A a;
+  // FIXME: OK, not odr-usable from a default template argument, and not odr-used
+  (void)[=]<typename T, int = a> {};
+  // since-cxx20-error@-1 {{call to deleted constructor of 'const A'}}
+  //   since-cxx20-note@#cwg2883-A-copy-ctor {{'A' has been explicitly marked deleted here}}
+}
+#endif
+} // namespace cwg2883
+
+namespace cwg2885 { // cwg2885: 16 tentatively ready 2024-05-31
+#if __cplusplus >= 202002L
+template <class T>
+struct A {
+  A() requires (false) = default;
+  A() : t(42) {}
+  T t;
+};
+
+struct B : A<int> {};
+static_assert(!__is_trivially_constructible(B));
+#endif
+} // namespace cwg2885
+
+namespace cwg2886 { // cwg2886: 9 tentatively ready 2024-05-31
+#if __cplusplus >= 201103L
+struct C {
+  C() = default;
+  ~C() noexcept(false) = default;
+};
+
+static_assert(noexcept(C()), "");
+#endif
+} // namespace cwg2886
diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 744d22959db42..4d94ac5a1ac1d 100755
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -17071,7 +17071,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2877.html">2877</a></td>
     <td>tentatively ready</td>
     <td>Type-only lookup for <I>using-enum-declarator</I></td>
-    <td align="center">Not resolved</td>
+    <td title="Clang does not implement 2024-05-31 resolution" align="center">Not Resolved*</td>
   </tr>
   <tr class="open" id="2878">
     <td><a href="https://cplusplus.github.io/CWG/issues/2878.html">2878</a></td>
@@ -17101,13 +17101,13 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2882.html">2882</a></td>
     <td>tentatively ready</td>
     <td>Unclear treatment of conversion to <TT>void</TT></td>
-    <td align="center">Not resolved</td>
+    <td title="Clang 2.7 implements 2024-05-31 resolution" align="center">Not Resolved*</td>
   </tr>
   <tr class="open" id="2883">
     <td><a href="https://cplusplus.github.io/CWG/issues/2883.html">2883</a></td>
     <td>tentatively ready</td>
     <td>Definition of "odr-usable" ignores lambda scopes</td>
-    <td align="center">Not resolved</td>
+    <td title="Clang does not implement 2024-05-31 resolution" align="center">Not Resolved*</td>
   </tr>
   <tr id="2884">
     <td><a href="https://cplusplus.github.io/CWG/issues/2884.html">2884</a></td>
@@ -17119,13 +17119,13 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/2885.html">2885</a></td>
     <td>tentatively ready</td>
     <td>Non-eligible trivial default constructors</td>
-    <td align="center">Not resolved</td>
+    <td title="Clang 16 implements 2024-05-31 resolution" align="center">Not Resolved*</td>
   </tr>
   <tr class="open" id="2886">
     <td><a href="https://cplusplus.github.io/CWG/issues/2886.html">2886</a></td>
     <td>tentatively ready</td>
     <td>Temporaries and trivial potentially-throwing special member functions</td>
-    <td align="center">Not resolved</td>
+    <td title="Clang 9 implements 2024-05-31 resolution" align="center">Not Resolved*</td>
   </tr>
   <tr class="open" id="2887">
     <td><a href="https://cplusplus.github.io/CWG/issues/2887.html">2887</a></td>

cor3ntin

LGTM, thanks!

cor3ntin · 2024-06-03T09:05:23Z

clang/test/CXX/drs/cwg28xx.cpp

+void g() {
+  constexpr A a;
+  // FIXME: OK, not odr-usable from a default template argument, and not odr-used
+  (void)[=]<typename T, int = a> {};
+  // since-cxx20-error@-1 {{call to deleted constructor of 'const A'}}
+  //   since-cxx20-note@#cwg2883-A-copy-ctor {{'A' has been explicitly marked deleted here}}
+}
+#endif
+} // namespace cwg2883


We do emit a diag later https://compiler-explorer.com/z/bd39GcqMP
I think it's still fair to say it's not implemented

#94203) In #94167 I found out that `cwg28xx.cpp` has been running without `-pedantic-errors` and fixed that. This patch fixes that for the rest of the test suite. Only one test was affected with a trivial fix (warning was escalated to an error). I'm intentionally leaving out test for CWG2390, because it requires major surgery. It's addressed in #94206.

shafik

LGTM, curious why you skipped some and not others from that telecom. Likely folks won't be able to check out the DRs until after St Louis.

[clang] Add tests for some CWG issues from 2024-05-31 telecon

df8a393

Endilll added test-suite c++ labels Jun 2, 2024

Endilll requested review from cor3ntin, AaronBallman, shafik, sdkrystian and Sirraide June 2, 2024 19:17

llvmbot added the clang Clang issues not falling into any other category label Jun 2, 2024

cor3ntin approved these changes Jun 3, 2024

View reviewed changes

Endilll merged commit 4f2dba3 into llvm:main Jun 3, 2024
11 checks passed

Endilll deleted the cwg2024-05-31 branch June 3, 2024 09:47

Endilll mentioned this pull request Jun 3, 2024

[clang] Make sure all C++ DR tests are running with -pedantic-errors #94203

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shafik reviewed Jun 4, 2024

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