[libcxx-commits] [libcxx] [libc++] Verify forward_list self-merging is a no-op (PR #129985)
Louis Dionne via libcxx-commits
libcxx-commits at lists.llvm.org
Wed Mar 19 09:27:07 PDT 2025
https://github.com/ldionne updated https://github.com/llvm/llvm-project/pull/129985
>From e813bed4aa8cf67fbfc265090a1b5610f3935abe Mon Sep 17 00:00:00 2001
From: Peng Liu <winner245 at hotmail.com>
Date: Wed, 5 Mar 2025 23:14:39 -0500
Subject: [PATCH 1/3] Verify forward_list self-merging is a no-op
---
libcxx/docs/Status/Cxx23Issues.csv | 2 +-
.../forwardlist/forwardlist.ops/merge_lvalue.pass.cpp | 8 ++++++++
.../forwardlist.ops/merge_lvalue_pred.pass.cpp | 9 ++++++++-
.../forwardlist/forwardlist.ops/merge_rvalue.pass.cpp | 8 ++++++++
.../forwardlist.ops/merge_rvalue_pred.pass.cpp | 8 ++++++++
5 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/libcxx/docs/Status/Cxx23Issues.csv b/libcxx/docs/Status/Cxx23Issues.csv
index 9ae6322b7fdbe..c0245035f60ae 100644
--- a/libcxx/docs/Status/Cxx23Issues.csv
+++ b/libcxx/docs/Status/Cxx23Issues.csv
@@ -137,7 +137,7 @@
"`LWG3593 <https://wg21.link/LWG3593>`__","Several iterators' ``base() const &`` and ``lazy_split_view::outer-iterator::value_type::end()`` missing ``noexcept``","2021-10 (Virtual)","","",""
"`LWG3595 <https://wg21.link/LWG3595>`__","Exposition-only classes proxy and postfix-proxy for ``common_iterator`` should be fully ``constexpr``","2021-10 (Virtual)","|Complete|","14",""
"","","","","",""
-"`LWG3088 <https://wg21.link/LWG3088>`__","``forward_list::merge`` behaviour unclear when passed ``*this``","2022-02 (Virtual)","","",""
+"`LWG3088 <https://wg21.link/LWG3088>`__","``forward_list::merge`` behaviour unclear when passed ``*this``","2022-02 (Virtual)","|Complete|","21",""
"`LWG3471 <https://wg21.link/LWG3471>`__","``polymorphic_allocator::allocate`` does not satisfy ``Cpp17Allocator`` requirements","2022-02 (Virtual)","","",""
"`LWG3525 <https://wg21.link/LWG3525>`__","``uses_allocator_construction_args`` fails to handle types convertible to ``pair``","2022-02 (Virtual)","","",""
"`LWG3598 <https://wg21.link/LWG3598>`__","``system_category().default_error_condition(0)`` is underspecified","2022-02 (Virtual)","","",""
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
index 6e73b2fd73726..541a5417db4e5 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
@@ -9,6 +9,7 @@
// <forward_list>
// void merge(forward_list& x);
+// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <iterator>
@@ -109,5 +110,12 @@ int main(int, char**) {
}
#endif
+ { // Make sure self-merging does nothing.
+ int a[] = {1, 2, 3, 4, 5};
+ std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ c.merge(c);
+ assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ }
+
return 0;
}
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
index fddf9f9dc0f46..22acb2836076b 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
@@ -9,6 +9,7 @@
// <forward_list>
// template <class Compare> void merge(forward_list& x, Compare comp);
+// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <iterator>
@@ -91,7 +92,6 @@ int main(int, char**) {
C c3(std::begin(t3), std::end(t3));
assert(c1 == c3);
}
-
#if TEST_STD_VER >= 11
{ // Test with a different allocator.
typedef int T;
@@ -110,5 +110,12 @@ int main(int, char**) {
}
#endif
+ { // Make sure self-merging does nothing.
+ int a[] = {5, 4, 3, 2, 1};
+ std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ c.merge(c, std::greater<int>());
+ assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ }
+
return 0;
}
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
index d5084eccd98da..995762e8a04e3 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
@@ -11,6 +11,7 @@
// <forward_list>
// void merge(forward_list&& x);
+// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <functional>
@@ -102,5 +103,12 @@ int main(int, char**) {
assert(c1 == c3);
}
+ { // Make sure self-merging does nothing.
+ int a[] = {1, 2, 3, 4, 5};
+ std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ c.merge(std::move(c));
+ assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ }
+
return 0;
}
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
index 235707c65370d..0ec466cefce2b 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
@@ -11,6 +11,7 @@
// <forward_list>
// template <class Compare> void merge(forward_list&& x, Compare comp);
+// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <functional>
@@ -103,5 +104,12 @@ int main(int, char**) {
assert(c1 == c3);
}
+ { // Make sure self-merging does nothing.
+ int a[] = {5, 4, 3, 2, 1};
+ std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ c.merge(std::move(c), std::greater<int>());
+ assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ }
+
return 0;
}
>From f05b9377f527fa78db283262e5102e6dadf0099a Mon Sep 17 00:00:00 2001
From: Peng Liu <winner245 at hotmail.com>
Date: Thu, 6 Mar 2025 13:42:58 -0500
Subject: [PATCH 2/3] Fix reviewer comments
---
libcxx/docs/Status/Cxx23Issues.csv | 2 +-
.../forwardlist/forwardlist.ops/merge_lvalue.pass.cpp | 5 ++---
.../forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp | 6 +++---
.../forwardlist/forwardlist.ops/merge_rvalue.pass.cpp | 5 ++---
.../forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp | 5 ++---
5 files changed, 10 insertions(+), 13 deletions(-)
diff --git a/libcxx/docs/Status/Cxx23Issues.csv b/libcxx/docs/Status/Cxx23Issues.csv
index c0245035f60ae..8cfc25099c034 100644
--- a/libcxx/docs/Status/Cxx23Issues.csv
+++ b/libcxx/docs/Status/Cxx23Issues.csv
@@ -137,7 +137,7 @@
"`LWG3593 <https://wg21.link/LWG3593>`__","Several iterators' ``base() const &`` and ``lazy_split_view::outer-iterator::value_type::end()`` missing ``noexcept``","2021-10 (Virtual)","","",""
"`LWG3595 <https://wg21.link/LWG3595>`__","Exposition-only classes proxy and postfix-proxy for ``common_iterator`` should be fully ``constexpr``","2021-10 (Virtual)","|Complete|","14",""
"","","","","",""
-"`LWG3088 <https://wg21.link/LWG3088>`__","``forward_list::merge`` behaviour unclear when passed ``*this``","2022-02 (Virtual)","|Complete|","21",""
+"`LWG3088 <https://wg21.link/LWG3088>`__","``forward_list::merge`` behaviour unclear when passed ``*this``","2022-02 (Virtual)","|Complete|","Yes",""
"`LWG3471 <https://wg21.link/LWG3471>`__","``polymorphic_allocator::allocate`` does not satisfy ``Cpp17Allocator`` requirements","2022-02 (Virtual)","","",""
"`LWG3525 <https://wg21.link/LWG3525>`__","``uses_allocator_construction_args`` fails to handle types convertible to ``pair``","2022-02 (Virtual)","","",""
"`LWG3598 <https://wg21.link/LWG3598>`__","``system_category().default_error_condition(0)`` is underspecified","2022-02 (Virtual)","","",""
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
index 541a5417db4e5..d7c06721da71b 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
@@ -9,7 +9,6 @@
// <forward_list>
// void merge(forward_list& x);
-// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <iterator>
@@ -112,9 +111,9 @@ int main(int, char**) {
{ // Make sure self-merging does nothing.
int a[] = {1, 2, 3, 4, 5};
- std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(c);
- assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ assert(c == std::forward_list<int>(std::begin(a), std::end(a)));
}
return 0;
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
index 22acb2836076b..f740969ea207e 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
@@ -9,7 +9,6 @@
// <forward_list>
// template <class Compare> void merge(forward_list& x, Compare comp);
-// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <iterator>
@@ -92,6 +91,7 @@ int main(int, char**) {
C c3(std::begin(t3), std::end(t3));
assert(c1 == c3);
}
+
#if TEST_STD_VER >= 11
{ // Test with a different allocator.
typedef int T;
@@ -112,9 +112,9 @@ int main(int, char**) {
{ // Make sure self-merging does nothing.
int a[] = {5, 4, 3, 2, 1};
- std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(c, std::greater<int>());
- assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ assert(c == std::forward_list<int>(std::begin(a), std::end(a)));
}
return 0;
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
index 995762e8a04e3..2dc2fa3303c71 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
@@ -11,7 +11,6 @@
// <forward_list>
// void merge(forward_list&& x);
-// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <functional>
@@ -105,9 +104,9 @@ int main(int, char**) {
{ // Make sure self-merging does nothing.
int a[] = {1, 2, 3, 4, 5};
- std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(std::move(c));
- assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ assert(c == std::forward_list<int>(std::begin(a), std::end(a)));
}
return 0;
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
index 0ec466cefce2b..8dee81750a989 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
@@ -11,7 +11,6 @@
// <forward_list>
// template <class Compare> void merge(forward_list&& x, Compare comp);
-// If (addressof(x) == this) does nothing; otherwise ...
#include <forward_list>
#include <functional>
@@ -106,9 +105,9 @@ int main(int, char**) {
{ // Make sure self-merging does nothing.
int a[] = {5, 4, 3, 2, 1};
- std::forward_list<int> c(a, a + sizeof(a) / sizeof(a[0]));
+ std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(std::move(c), std::greater<int>());
- assert((c == std::forward_list<int>(a, a + sizeof(a) / sizeof(a[0]))));
+ assert(c == std::forward_list<int>(std::begin(a), std::end(a)));
}
return 0;
>From 5576cf0cd20c216d4f2a82bcea47f6f64e2897d5 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Wed, 19 Mar 2025 12:26:57 -0400
Subject: [PATCH 3/3] Apply suggestions from code review
---
.../sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp | 2 +-
.../forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp | 2 +-
.../sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp | 2 +-
.../forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp | 2 +-
4 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
index d7c06721da71b..9a162789569d3 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue.pass.cpp
@@ -109,7 +109,7 @@ int main(int, char**) {
}
#endif
- { // Make sure self-merging does nothing.
+ { // LWG3088: Make sure self-merging does nothing.
int a[] = {1, 2, 3, 4, 5};
std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(c);
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
index f740969ea207e..4e1814044808c 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_lvalue_pred.pass.cpp
@@ -110,7 +110,7 @@ int main(int, char**) {
}
#endif
- { // Make sure self-merging does nothing.
+ { // LWG3088: Make sure self-merging does nothing.
int a[] = {5, 4, 3, 2, 1};
std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(c, std::greater<int>());
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
index 2dc2fa3303c71..acfa014fe2546 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue.pass.cpp
@@ -102,7 +102,7 @@ int main(int, char**) {
assert(c1 == c3);
}
- { // Make sure self-merging does nothing.
+ { // LWG3088: Make sure self-merging does nothing.
int a[] = {1, 2, 3, 4, 5};
std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(std::move(c));
diff --git a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
index 8dee81750a989..41b56ce7a2884 100644
--- a/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
+++ b/libcxx/test/std/containers/sequences/forwardlist/forwardlist.ops/merge_rvalue_pred.pass.cpp
@@ -103,7 +103,7 @@ int main(int, char**) {
assert(c1 == c3);
}
- { // Make sure self-merging does nothing.
+ { // LWG3088: Make sure self-merging does nothing.
int a[] = {5, 4, 3, 2, 1};
std::forward_list<int> c(std::begin(a), std::end(a));
c.merge(std::move(c), std::greater<int>());
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