[clang] [clang] Implement P3176R1: The Oxford variadic comma (PR #117524)
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Sun Nov 24 23:21:05 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: None (antangelo)
<details>
<summary>Changes</summary>
Emit a deprecation warning when a variadic parameter in a parameter-declaration-clause is not preceded by a comma for C++26.
---
Full diff: https://github.com/llvm/llvm-project/pull/117524.diff
7 Files Affected:
- (modified) clang/docs/ReleaseNotes.rst (+2)
- (modified) clang/include/clang/Basic/DiagnosticGroups.td (+3-1)
- (modified) clang/include/clang/Basic/DiagnosticParseKinds.td (+3)
- (modified) clang/lib/Parse/ParseDecl.cpp (+8)
- (modified) clang/test/CXX/drs/cwg722.cpp (+1-1)
- (added) clang/test/Parser/cxx2c-oxford-variadic-comma.cpp (+36)
- (modified) clang/www/cxx_status.html (+1-1)
``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8bd06fadfdc984..b8d5c4201aeaef 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -227,6 +227,8 @@ C++2c Feature Support
- Added the ``__builtin_is_within_lifetime`` builtin, which supports
`P2641R4 Checking if a union alternative is active <https://wg21.link/p2641r4>`_
+- Implemented `P3176R1 The Oxford variadic comma <https://wg21.link/P3176R1>`_
+
C++23 Feature Support
^^^^^^^^^^^^^^^^^^^^^
- Removed the restriction to literal types in constexpr functions in C++23 mode.
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index df9bf94b5d0398..7ad8ac0e7a2e46 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -211,6 +211,7 @@ def DeprecatedWritableStr : DiagGroup<"deprecated-writable-strings",
[CXX11CompatDeprecatedWritableStr]>;
def DeprecatedPragma : DiagGroup<"deprecated-pragma">;
def DeprecatedType : DiagGroup<"deprecated-type">;
+def DeprecatedMissingCommaVariadicParam : DiagGroup<"deprecated-missing-comma-variadic-parameter">;
// FIXME: Why is DeprecatedImplementations not in this group?
def Deprecated : DiagGroup<"deprecated", [DeprecatedAnonEnumEnumConversion,
DeprecatedArrayCompare,
@@ -235,7 +236,8 @@ def Deprecated : DiagGroup<"deprecated", [DeprecatedAnonEnumEnumConversion,
DeprecatedType,
DeprecatedVolatile,
DeprecatedWritableStr,
- DeprecatedRedundantConstexprStaticDef
+ DeprecatedRedundantConstexprStaticDef,
+ DeprecatedMissingCommaVariadicParam
]>,
DiagCategory<"Deprecations">;
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 77bf08453dea51..7c3961059d1d0d 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -413,6 +413,9 @@ def err_function_scope_depth_exceeded : Error<
"function scope depth exceeded maximum of %0">, DefaultFatal;
def err_missing_comma_before_ellipsis : Error<
"C requires a comma prior to the ellipsis in a variadic function type">;
+def warn_deprecated_missing_comma_before_ellipsis : Warning<
+ "variadic parameters that are not preceded by a comma are deprecated">,
+ InGroup<DeprecatedMissingCommaVariadicParam>;
def err_unexpected_typedef_ident : Error<
"unexpected type name %0: expected identifier">;
def warn_cxx98_compat_decltype : Warning<
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index aa5c2d28d429ac..d28a74662aefe0 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -8119,6 +8119,14 @@ void Parser::ParseParameterDeclarationClause(
}
if (TryConsumeToken(tok::ellipsis, EllipsisLoc)) {
+ if (getLangOpts().CPlusPlus26) {
+ // C++26 [dcl.dcl.fct]p3:
+ // A parameter-declaration-clause of the form
+ // parameter-list '...' is deprecated
+ Diag(EllipsisLoc, diag::warn_deprecated_missing_comma_before_ellipsis)
+ << FixItHint::CreateInsertion(EllipsisLoc, ", ");
+ }
+
if (!getLangOpts().CPlusPlus) {
// We have ellipsis without a preceding ',', which is ill-formed
// in C. Complain and provide the fix.
diff --git a/clang/test/CXX/drs/cwg722.cpp b/clang/test/CXX/drs/cwg722.cpp
index e90d9af360d9d0..6e7d4569c55381 100644
--- a/clang/test/CXX/drs/cwg722.cpp
+++ b/clang/test/CXX/drs/cwg722.cpp
@@ -14,7 +14,7 @@ namespace std {
using nullptr_t = decltype(nullptr);
}
-void f(std::nullptr_t...);
+void f(std::nullptr_t, ...);
std::nullptr_t g();
void h() {
std::nullptr_t np;
diff --git a/clang/test/Parser/cxx2c-oxford-variadic-comma.cpp b/clang/test/Parser/cxx2c-oxford-variadic-comma.cpp
new file mode 100644
index 00000000000000..dc78dcbb6b074f
--- /dev/null
+++ b/clang/test/Parser/cxx2c-oxford-variadic-comma.cpp
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -std=c++2c -fsyntax-only -verify %s
+
+void a(...);
+
+void b(auto...);
+void c(auto, ...);
+
+void d(auto......); // expected-warning {{variadic parameters that are not preceded by a comma are deprecated}} \
+ // expected-warning {{'...' in this location creates a C-style varargs function}} \
+ // expected-note {{preceding '...' declares a function parameter pack}} \
+ // expected-note {{insert ',' before '...' to silence this warning}}
+void e(auto..., ...);
+
+void f(auto x...); // expected-warning {{variadic parameters that are not preceded by a comma are deprecated}}
+void g(auto x, ...);
+
+void h(auto... x...); // expected-warning {{variadic parameters that are not preceded by a comma are deprecated}} \
+ // expected-warning {{'...' in this location creates a C-style varargs function}} \
+ // expected-note {{preceding '...' declares a function parameter pack}} \
+ // expected-note {{insert ',' before '...' to silence this warning}}
+void i(auto... x, ...);
+
+template<class ...T>
+void j(T... t...); // expected-warning {{variadic parameters that are not preceded by a comma are deprecated}} \
+ // expected-warning {{'...' in this location creates a C-style varargs function}} \
+ // expected-note {{preceding '...' declares a function parameter pack}} \
+ // expected-note {{insert ',' before '...' to silence this warning}}
+template<class ...T>
+void k(T... t, ...);
+
+void l(int...); // expected-warning {{variadic parameters that are not preceded by a comma are deprecated}}
+void m(int, ...);
+
+void n(int x...); // expected-warning {{variadic parameters that are not preceded by a comma are deprecated}}
+void o(int x, ...);
+
diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html
index da01cf6ceab59b..fdb9807b1168c7 100755
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -249,7 +249,7 @@ <h2 id="cxx26">C++2c implementation status</h2>
<tr>
<td>The Oxford variadic comma</td>
<td><a href="https://wg21.link/P3176R1">P3176R1</a></td>
- <td class="none" align="center">No</td>
+ <td class="unreleased" align="center">Clang 20</td>
</tr>
</table>
</details>
``````````
</details>
https://github.com/llvm/llvm-project/pull/117524
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