[libcxx-commits] [PATCH] D74287: [libcxx] Fix unintended ADL inside ref(reference_wrapper<T>) and cref(reference_wrapper<T>)

[Logan Smith via Phabricator via libcxx-commits]

logan-5 created this revision.
logan-5 added reviewers: EricWF, mclow.lists.
logan-5 added a project: libc++.
Herald added subscribers: libcxx-commits, ldionne, christof.

This patch qualifies calls to `ref` and `cref` inside `ref(reference_wrapper<T>)` and `cref(reference_wrapper<T>)`, respectively. These previously unqualified calls could break in the presence of user functions called ref/cref inside associated namespaces: https://gcc.godbolt.org/z/8VfprT

Fixes https://bugs.llvm.org/show_bug.cgi?id=44398.

Thanks to @Quuxplusone for creating that Godbolt test case and submitting the bug.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74287

Files:
  libcxx/include/__functional_base
  libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/cref_2.pass.cpp
  libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/ref_2.pass.cpp


Index: libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/ref_2.pass.cpp
===================================================================
--- libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/ref_2.pass.cpp
+++ libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/ref_2.pass.cpp
@@ -24,6 +24,11 @@
 template <typename T>
 bool call_pred ( T pred ) { return pred(5); }
 
+namespace adl {
+  struct A {};
+  void ref(A) {}
+}
+
 int main(int, char**)
 {
     {
@@ -32,6 +37,13 @@
     std::reference_wrapper<int> r2 = std::ref(r1);
     assert(&r2.get() == &i);
     }
+    {
+    adl::A a;
+    std::reference_wrapper<adl::A> a1 = std::ref(a);
+    std::reference_wrapper<adl::A> a2 = std::ref(a1);
+    assert(&a2.get() == &a);
+    }
+
     {
     unary_counting_predicate<bool(*)(int), int> cp(is5);
     assert(!cp(6));
Index: libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/cref_2.pass.cpp
===================================================================
--- libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/cref_2.pass.cpp
+++ libcxx/test/std/utilities/function.objects/refwrap/refwrap.helpers/cref_2.pass.cpp
@@ -17,6 +17,11 @@
 
 #include "test_macros.h"
 
+namespace adl {
+  struct A {};
+  void cref(A) {}
+}
+
 int main(int, char**)
 {
     const int i = 0;
@@ -24,5 +29,12 @@
     std::reference_wrapper<const int> r2 = std::cref(r1);
     assert(&r2.get() == &i);
 
+    {
+    adl::A a;
+    std::reference_wrapper<const adl::A> a1 = std::cref(a);
+    std::reference_wrapper<const adl::A> a2 = std::cref(a1);
+    assert(&a2.get() == &a);
+    }
+
   return 0;
 }
Index: libcxx/include/__functional_base
===================================================================
--- libcxx/include/__functional_base
+++ libcxx/include/__functional_base
@@ -522,7 +522,7 @@
 reference_wrapper<_Tp>
 ref(reference_wrapper<_Tp> __t) _NOEXCEPT
 {
-    return ref(__t.get());
+    return _VSTD::ref(__t.get());
 }
 
 template <class _Tp>
@@ -538,7 +538,7 @@
 reference_wrapper<const _Tp>
 cref(reference_wrapper<_Tp> __t) _NOEXCEPT
 {
-    return cref(__t.get());
+    return _VSTD::cref(__t.get());
 }
 
 #ifndef _LIBCPP_CXX03_LANG


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