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rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D79800/new/
https://reviews.llvm.org/D79800
Files:
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/CXX/drs/dr22xx.cpp
clang/test/CXX/drs/dr7xx.cpp
clang/www/cxx_dr_status.html
Index: clang/www/cxx_dr_status.html
===================================================================
--- clang/www/cxx_dr_status.html
+++ clang/www/cxx_dr_status.html
@@ -4681,7 +4681,7 @@
<td><a href="https://wg21.link/cwg777";>777</a></td>
<td>CD2</td>
<td>Default arguments and parameter packs</td>
- <td class="full" align="center">Clang 3.7</td>
+ <td class="full" align="center">Superseded by <a href="#2233">2233</a></td>
</tr>
<tr id="778">
<td><a href="https://wg21.link/cwg778";>778</a></td>
@@ -13213,7 +13213,7 @@
<td><a href="https://wg21.link/cwg2233";>2233</a></td>
<td>DRWP</td>
<td>Function parameter packs following default arguments</td>
- <td class="none" align="center">Unknown</td>
+ <td class="full" align="center">Clang 11</td>
</tr>
<tr id="2234">
<td><a href="https://wg21.link/cwg2234";>2234</a></td>
Index: clang/test/CXX/drs/dr7xx.cpp
===================================================================
--- clang/test/CXX/drs/dr7xx.cpp
+++ clang/test/CXX/drs/dr7xx.cpp
@@ -219,16 +219,4 @@
Collision<int, int> c; // expected-note {{in instantiation of}}
}
-namespace dr777 { // dr777: 3.7
-#if __cplusplus >= 201103L
-template <typename... T>
-void f(int i = 0, T ...args) {}
-void ff() { f(); }
-
-template <typename... T>
-void g(int i = 0, T ...args, T ...args2) {}
-
-template <typename... T>
-void h(int i = 0, T ...args, int j = 1) {}
-#endif
-}
+// dr777 superseded by dr2233
Index: clang/test/CXX/drs/dr22xx.cpp
===================================================================
--- clang/test/CXX/drs/dr22xx.cpp
+++ clang/test/CXX/drs/dr22xx.cpp
@@ -35,3 +35,44 @@
}
#endif
}
+
+namespace dr2233 { // dr2233: 11
+#if __cplusplus >= 201103L
+template <typename... T>
+void f(int i = 0, T... args) {}
+
+template <typename... T>
+void g(int i = 0, T... args, T... args2) {}
+
+template <typename... T>
+void h(int i = 0, T... args, int j = 1) {}
+
+template <typename... T, typename... U>
+void i(int i = 0, T... args, int j = 1, U... args2) {}
+
+template <class... Ts>
+void j(int i = 0, Ts... ts) {}
+
+template <>
+void j<int>(int i, int j) {}
+
+// PR23029
+// Ensure instantiating the templates works.
+void use() {
+ f();
+ f(0, 1);
+ f<int>(1, 2);
+ g<int>(1, 2, 3);
+ h(0, 1);
+ i();
+ i(3);
+ i<int>(3, 2);
+ i<int>(3, 2, 1);
+ i<int, int>(1, 2, 3, 4, 5);
+ j();
+ j(1);
+ j(1, 2);
+ j<int>(1, 2);
+}
+#endif
+} // namespace dr2233
Index: clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1974,6 +1974,48 @@
TemplateArgumentList::CreateCopy(SemaRef.Context,
Innermost),
/*InsertPos=*/nullptr);
+
+ // DR777, DR2233.
+ // Parameter packs are allowed after and inbetween parameters with default
+ // values. We need to remove default arguments for parameters before the
+ // first expanded parameter pack to prevent the declaration being diagnosed
+ // as invalid due to the expanded parameters after parameters with default
+ // values lacking default values. This is safe to do because if a parameter
+ // pack is expanded the user must've provided arguments for all parameters
+ // before it.
+ FunctionDecl *TemplatedDecl = FunctionTemplate->getTemplatedDecl();
+ unsigned FirstPack = Function->getNumParams();
+ bool RemoveDefaults = false;
+
+ // Go backwards through the template declaration parameters and find the
+ // first parameter pack, which has non-zero number of arguments.
+ for (unsigned p = TemplatedDecl->getNumParams(); p-- > 0;) {
+ ParmVarDecl *Param = TemplatedDecl->getParamDecl(p);
+
+ if (Param->isParameterPack()) {
+ llvm::Optional<unsigned> Args =
+ SemaRef.getNumArgumentsInExpansion(Param->getType(), TemplateArgs);
+ assert(Args != None && "Unknown number of pack expansion arguments.");
+
+ if (Args.getValue() == 0)
+ continue;
+
+ FirstPack -= Args.getValue();
+ RemoveDefaults = true;
+ break;
+ } else {
+ FirstPack--;
+ }
+ }
+
+ // If we found such a parameter pack, then remove default arguments for all
+ // parameters before it.
+ if (RemoveDefaults) {
+ for (unsigned p = 0; p < FirstPack; p++) {
+ ParmVarDecl *Param = Function->getParamDecl(p);
+ Param->setDefaultArg(nullptr);
+ }
+ }
} else if (isFriend && D->isThisDeclarationADefinition()) {
// Do not connect the friend to the template unless it's actually a
// definition. We don't want non-template functions to be marked as being
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