https://gcc.gnu.org/g:27f6b376e8e196c7c85c8b47436cd2f2993768da
commit r15-4303-g27f6b376e8e196c7c85c8b47436cd2f2993768da
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Sun Oct 13 19:14:04 2024 +0100
libstdc++: Fix ranges::copy_backward for a single memcpyable element
[PR117121]
The result iterator needs to be decremented before writing to it.
Improve the PR 108846 tests for all of std::copy, std::copy_n,
std::copy_backward, and the std::ranges versions.
libstdc++-v3/ChangeLog:
PR libstdc++/117121
* include/bits/ranges_algobase.h (copy_backward): Decrement
output iterator before assigning one element through it.
* testsuite/25_algorithms/copy/108846.cc: Ensure the algorithm's
effects are correct for a single memcpyable element.
* testsuite/25_algorithms/copy_backward/108846.cc: Likewise.
* testsuite/25_algorithms/copy_n/108846.cc: Likewise.
Diff:
---
libstdc++-v3/include/bits/ranges_algobase.h | 5 +++--
libstdc++-v3/testsuite/25_algorithms/copy/108846.cc | 15 +++++++++++++++
.../testsuite/25_algorithms/copy_backward/108846.cc | 15 +++++++++++++++
libstdc++-v3/testsuite/25_algorithms/copy_n/108846.cc | 15 +++++++++++++++
4 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/include/bits/ranges_algobase.h
b/libstdc++-v3/include/bits/ranges_algobase.h
index 40c628b38182..3c8d46198c5d 100644
--- a/libstdc++-v3/include/bits/ranges_algobase.h
+++ b/libstdc++-v3/include/bits/ranges_algobase.h
@@ -418,12 +418,13 @@ namespace ranges
{
using _ValueTypeI = iter_value_t<_Iter>;
auto __num = __last - __first;
+ __result -= __num;
if (__num > 1) [[likely]]
- __builtin_memmove(__result - __num, __first,
+ __builtin_memmove(__result, __first,
sizeof(_ValueTypeI) * __num);
else if (__num == 1)
ranges::__assign_one<_IsMove>(__first, __result);
- return {__first + __num, __result - __num};
+ return {__first + __num, __result};
}
}
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy/108846.cc
b/libstdc++-v3/testsuite/25_algorithms/copy/108846.cc
index e3b722c068ab..a283e6fcd9fb 100644
--- a/libstdc++-v3/testsuite/25_algorithms/copy/108846.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/copy/108846.cc
@@ -25,10 +25,15 @@ test_pr108846()
B *src = &dsrc;
// If this is optimized to memmove it will overwrite tail padding.
std::copy(src, src+1, dst);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy(src, src+1, dst);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
@@ -52,10 +57,15 @@ test_non_const_copy_assign()
B2 *src = &dsrc;
// Ensure the not-taken trivial copy path works for this type.
std::copy(src, src+1, dst);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy(src, src+1, dst);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
@@ -81,10 +91,15 @@ test_non_const_copy_assign_trivial()
B3 *src = &dsrc;
// If this is optimized to memmove it will overwrite tail padding.
std::copy(src, src+1, dst);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy(src, src+1, dst);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy_backward/108846.cc
b/libstdc++-v3/testsuite/25_algorithms/copy_backward/108846.cc
index 206748d92d33..855ee3e182f7 100644
--- a/libstdc++-v3/testsuite/25_algorithms/copy_backward/108846.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/copy_backward/108846.cc
@@ -25,10 +25,15 @@ test_pr108846()
B *src = &dsrc;
// If this is optimized to memmove it will overwrite tail padding.
std::copy_backward(src, src+1, dst+1);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy_backward(src, src+1, dst+1);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
@@ -52,10 +57,15 @@ test_non_const_copy_assign()
B2 *src = &dsrc;
// Ensure the not-taken trivial copy path works for this type.
std::copy_backward(src, src+1, dst+1);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy_backward(src, src+1, dst+1);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
@@ -81,10 +91,15 @@ test_non_const_copy_assign_trivial()
B3 *src = &dsrc;
// If this is optimized to memmove it will overwrite tail padding.
std::copy_backward(src, src+1, dst+1);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy_backward(src, src+1, dst+1);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy_n/108846.cc
b/libstdc++-v3/testsuite/25_algorithms/copy_n/108846.cc
index 50deb5dd0510..d46fb9006e2d 100644
--- a/libstdc++-v3/testsuite/25_algorithms/copy_n/108846.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/copy_n/108846.cc
@@ -25,10 +25,15 @@ test_pr108846()
B *src = &dsrc;
// If this is optimized to memmove it will overwrite tail padding.
std::copy_n(src, 1, dst);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy_n(src, 1, dst);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
@@ -52,10 +57,15 @@ test_non_const_copy_assign()
B2 *src = &dsrc;
// Ensure the not-taken trivial copy path works for this type.
std::copy_n(src, 1, dst);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy_n(src, 1, dst);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
@@ -79,10 +89,15 @@ test_non_const_copy_assign_trivial()
B3 *src = &dsrc;
// If this is optimized to memmove it will overwrite tail padding.
std::copy_n(src, 1, dst);
+ // Check tail padding is unchanged:
VERIFY(ddst.x == 3);
+ // Check B subobject was copied:
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#if __cpp_lib_ranges >= 201911L
+ ddst.i = ddst.j = 99;
std::ranges::copy_n(src, 1, dst);
VERIFY(ddst.x == 3);
+ VERIFY(ddst.i == 4 && ddst.j == 5);
#endif
}
