The three-argument form of ranges::advance is supposed to return the
difference between the second argument and the distance the iterator was
advanced. When a non-random-access iterator is not advanced (because it
already equals the sentinel) we were returning 0 rather than n - 0.
libstdc++-v3/ChangeLog:
PR libstdc++/100833
* include/bits/ranges_base.h (ranges::advance(iter, n, sentinel)):
Fix return value for no-op case.
* testsuite/24_iterators/range_operations/advance.cc: Test
return values of three-argument overload.
Tested powerpc64le-linux. Committed to trunk.
commit d8326291695c0f13124c232ddf4fd34e3310e649
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Tue Jun 1 16:02:45 2021
libstdc++: Fix return value of std::ranges::advance [PR 100833]
The three-argument form of ranges::advance is supposed to return the
difference between the second argument and the distance the iterator was
advanced. When a non-random-access iterator is not advanced (because it
already equals the sentinel) we were returning 0 rather than n - 0.
libstdc++-v3/ChangeLog:
PR libstdc++/100833
* include/bits/ranges_base.h (ranges::advance(iter, n, sentinel)):
Fix return value for no-op case.
* testsuite/24_iterators/range_operations/advance.cc: Test
return values of three-argument overload.
diff --git a/libstdc++-v3/include/bits/ranges_base.h
b/libstdc++-v3/include/bits/ranges_base.h
index 11f05fa4e2d..32d664f1a86 100644
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -749,7 +749,7 @@ namespace ranges
}
}
else if (__it == __bound || __n == 0)
- return iter_difference_t<_It>(0);
+ return __n;
else if (__n > 0)
{
iter_difference_t<_It> __m = 0;
diff --git a/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
b/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
index e4abf83d59e..feee08b58c4 100644
--- a/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
+++ b/libstdc++-v3/testsuite/24_iterators/range_operations/advance.cc
@@ -49,10 +49,12 @@ test01()
std::ranges::advance(iter, r.begin());
VERIFY( iter == r.begin() );
- std::ranges::advance(iter, 99, r.end());
+ auto diff = std::ranges::advance(iter, 99, r.end());
VERIFY( iter == r.end() );
- std::ranges::advance(iter, -222, r.begin());
+ VERIFY( diff == 97 );
+ diff = std::ranges::advance(iter, -222, r.begin());
VERIFY( iter == r.begin() );
+ VERIFY( diff == -220 );
}
void
@@ -77,10 +79,12 @@ test02()
std::ranges::advance(iter, r.begin());
VERIFY( iter == r.begin() );
- std::ranges::advance(iter, 99, r.end());
+ auto diff = std::ranges::advance(iter, 99, r.end());
VERIFY( iter == r.end() );
- std::ranges::advance(iter, -222, r.begin());
+ VERIFY( diff == 97 );
+ diff = std::ranges::advance(iter, -222, r.begin());
VERIFY( iter == r.begin() );
+ VERIFY( diff == -220 );
}
void
@@ -108,15 +112,19 @@ test03()
std::ranges::advance(iter, r.end());
VERIFY( iter == r.end() );
- std::ranges::advance(iter, 99, r.end());
+ auto diff = std::ranges::advance(iter, 99, r.end());
VERIFY( iter == r.end() );
- std::ranges::advance(iter, 99, r.end());
+ VERIFY( diff == 99 ); // PR libstdc++/100833
+ diff = std::ranges::advance(iter, 99, r.end());
VERIFY( iter == r.end() );
+ VERIFY( diff == 99 );
iter = r.begin();
- std::ranges::advance(iter, 99, r.end());
+ diff = std::ranges::advance(iter, 99, r.end());
VERIFY( iter == r.end() );
- std::ranges::advance(iter, 99, r.end());
+ VERIFY( diff == 97 );
+ diff = std::ranges::advance(iter, 99, r.end());
VERIFY( iter == r.end() );
+ VERIFY( diff == 99 );
}
void
@@ -145,17 +153,21 @@ test04()
std::ranges::advance(iter, r2.end());
VERIFY( iter == r2.end() );
- std::ranges::advance(iter, 99, r2.end());
+ auto diff = std::ranges::advance(iter, 99, r2.end());
VERIFY( iter == r2.end() );
- std::ranges::advance(iter, 99, r2.end());
+ VERIFY( diff == 99 );
+ diff = std::ranges::advance(iter, 99, r2.end());
VERIFY( iter == r2.end() );
+ VERIFY( diff == 99 );
test_range<int, input_iterator_wrapper> r3(a);
iter = r3.begin();
- std::ranges::advance(iter, 99, r3.end());
+ diff = std::ranges::advance(iter, 99, r3.end());
VERIFY( iter == r3.end() );
- std::ranges::advance(iter, 99, r3.end());
+ VERIFY( diff == 97 );
+ diff = std::ranges::advance(iter, 99, r3.end());
VERIFY( iter == r3.end() );
+ VERIFY( diff == 99 );
}
void
@@ -180,17 +192,21 @@ test05()
std::ranges::advance(iter, r2.end());
VERIFY( iter == r2.end() );
- std::ranges::advance(iter, 99, r2.end());
+ auto diff = std::ranges::advance(iter, 99, r2.end());
VERIFY( iter == r2.end() );
- std::ranges::advance(iter, 99, r2.end());
+ VERIFY( diff == 99 );
+ diff = std::ranges::advance(iter, 99, r2.end());
VERIFY( iter == r2.end() );
+ VERIFY( diff == 99 );
test_range<int, output_iterator_wrapper> r3(a);
iter = r3.begin();
- std::ranges::advance(iter, 99, r3.end());
+ diff = std::ranges::advance(iter, 99, r3.end());
VERIFY( iter == r3.end() );
- std::ranges::advance(iter, 99, r3.end());
+ VERIFY( diff == 97 );
+ diff = std::ranges::advance(iter, 99, r3.end());
VERIFY( iter == r3.end() );
+ VERIFY( diff == 99 );
}
int
