[gcc(refs/users/giulianob/heads/autopar_rebase2)] libstdc++: Implement P0966 std::string::reserve should not shrink
Giuliano Belinassi
giulianob@gcc.gnu.org
Tue Aug 18 01:32:26 GMT 2020
https://gcc.gnu.org/g:886ef00cea4e777e7b90be13bc3f7c220226cc36
commit 886ef00cea4e777e7b90be13bc3f7c220226cc36
Author: Andrew Luo <andrewluotechnologies@outlook.com>
Date: Thu Aug 6 19:35:43 2020 +0100
libstdc++: Implement P0966 std::string::reserve should not shrink
Remove ability for reserve(n) to reduce a string's capacity. Add a new
reserve() overload that makes a shrink-to-fit request, and make
shrink_to_fit() use that.
libstdc++-v3/ChangeLog:
2020-07-30 Andrew Luo <andrewluotechnologies@outlook.com>
Jonathan Wakely <jwakely@redhat.com>
* config/abi/pre/gnu.ver (GLIBCXX_3.4): Use less greedy
patterns for basic_string members.
(GLIBCXX_3.4.29): Export new basic_string::reserve symbols.
* doc/xml/manual/status_cxx2020.xml: Update P0966 status.
* include/bits/basic_string.h (shrink_to_fit()): Call reserve().
(reserve(size_type)): Remove default argument.
(reserve()): Declare new overload.
[!_GLIBCXX_USE_CXX11_ABI] (shrink_to_fit, reserve): Likewise.
* include/bits/basic_string.tcc (reserve(size_type)): Remove
support for shrinking capacity.
(reserve()): Perform shrink-to-fit operation.
[!_GLIBCXX_USE_CXX11_ABI] (reserve): Likewise.
* testsuite/21_strings/basic_string/capacity/1.cc: Adjust to
reflect new behavior.
* testsuite/21_strings/basic_string/capacity/char/1.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/char/18654.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/char/2.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/wchar_t/1.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/wchar_t/18654.cc:
Likewise.
* testsuite/21_strings/basic_string/capacity/wchar_t/2.cc:
Likewise.
Diff:
---
libstdc++-v3/config/abi/pre/gnu.ver | 17 ++-
libstdc++-v3/doc/xml/manual/status_cxx2020.xml | 3 +-
libstdc++-v3/include/bits/basic_string.h | 52 ++++-----
libstdc++-v3/include/bits/basic_string.tcc | 119 +++++++++++++++------
.../21_strings/basic_string/capacity/1.cc | 14 ++-
.../21_strings/basic_string/capacity/char/1.cc | 14 ++-
.../21_strings/basic_string/capacity/char/18654.cc | 8 +-
.../21_strings/basic_string/capacity/char/2.cc | 6 +-
.../21_strings/basic_string/capacity/wchar_t/1.cc | 14 ++-
.../basic_string/capacity/wchar_t/18654.cc | 8 +-
.../21_strings/basic_string/capacity/wchar_t/2.cc | 6 +-
11 files changed, 182 insertions(+), 79 deletions(-)
diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index b6ce76c1f20..b582f53e363 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -223,7 +223,10 @@ GLIBCXX_3.4 {
_ZNSs6assignE[PRcjmvy]*;
_ZNSs6insertE[PRcjmvy]*;
_ZNSs6insertEN9__gnu_cxx17__normal_iteratorIPcSsEE[PRcjmvy]*;
- _ZNSs[67][j-z]*E[PRcjmvy]*;
+ _ZNSs6rbeginEv;
+ _ZNSs6resizeE[jmy]*;
+ _ZNSs7replaceE[jmy]*;
+ _ZNSs7reserveE[jmy];
_ZNSs7[a-z]*EES2_[NPRjmy]*;
_ZNSs7[a-z]*EES2_S[12]*;
_ZNSs12_Alloc_hiderC*;
@@ -290,7 +293,10 @@ GLIBCXX_3.4 {
_ZNSbIwSt11char_traitsIwESaIwEE6assignE[PRwjmvy]*;
_ZNSbIwSt11char_traitsIwESaIwEE6insertE[PRwjmvy]*;
_ZNSbIwSt11char_traitsIwESaIwEE6insertEN9__gnu_cxx17__normal_iteratorIPwS2_EE[PRwjmvy]*;
- _ZNSbIwSt11char_traitsIwESaIwEE[67][j-z]*E[PRwjmvy]*;
+ _ZNSbIwSt11char_traitsIwESaIwEE6rbeginEv;
+ _ZNSbIwSt11char_traitsIwESaIwEE7replaceEmm[PRm]*;
+ _ZNSbIwSt11char_traitsIwESaIwEE6resizeEm*;
+ _ZNSbIwSt11char_traitsIwESaIwEE7reserveEm;
_ZNSbIwSt11char_traitsIwESaIwEE7[a-z]*EES6_[NPRjmy]*;
_ZNSbIwSt11char_traitsIwESaIwEE7[a-z]*EES6_S[56]*;
_ZNSbIwSt11char_traitsIwESaIwEE12_Alloc_hiderC*;
@@ -1740,7 +1746,7 @@ GLIBCXX_3.4.21 {
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE6rbegin*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE6resize*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE7replace*;
- _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE7reserve*;
+ _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE7reserveE[jmy];
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE8pop_back*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE9push_back*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE[7-9]_[MS]_*;
@@ -2309,6 +2315,11 @@ GLIBCXX_3.4.29 {
# std::__istream_extract(wistream&, wchar_t*, streamsize)
_ZSt17__istream_extractIwSt11char_traitsIwEEvRSt13basic_istreamIT_T0_EPS3_[ilx];
+ # basic_string::reserve()
+ _ZNSs7reserveEv;
+ _ZNSbIwSt11char_traitsIwESaIwEE7reserveEv;
+ _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE7reserveEv;
+
} GLIBCXX_3.4.28;
# Symbols in the support library (libsupc++) have their own tag.
diff --git a/libstdc++-v3/doc/xml/manual/status_cxx2020.xml b/libstdc++-v3/doc/xml/manual/status_cxx2020.xml
index ade77cbb80b..b9ad03c720f 100644
--- a/libstdc++-v3/doc/xml/manual/status_cxx2020.xml
+++ b/libstdc++-v3/doc/xml/manual/status_cxx2020.xml
@@ -635,13 +635,12 @@ or any notes about the implementation.
</row>
<row>
- <?dbhtml bgcolor="#C8B0B0" ?>
<entry> <code>string::reserve</code> Should Not Shrink </entry>
<entry>
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0966r1.html">
P0966R1 </link>
</entry>
- <entry align="center"> </entry>
+ <entry align="center"> 11 </entry>
<entry />
</row>
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 52cecdd7ca1..e34b5c1fca3 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -940,20 +940,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ this->resize(__n, _CharT()); }
#if __cplusplus >= 201103L
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
/// A non-binding request to reduce capacity() to size().
void
shrink_to_fit() noexcept
- {
-#if __cpp_exceptions
- if (capacity() > size())
- {
- try
- { reserve(0); }
- catch(...)
- { }
- }
-#endif
- }
+ { reserve(); }
+#pragma GCC diagnostic pop
#endif
/**
@@ -985,7 +978,16 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
* data.
*/
void
- reserve(size_type __res_arg = 0);
+ reserve(size_type __res_arg);
+
+ /**
+ * Equivalent to shrink_to_fit().
+ */
+#if __cplusplus > 201703L
+ [[deprecated("use shrink_to_fit() instead")]]
+#endif
+ void
+ reserve();
/**
* Erases the string, making it empty.
@@ -3942,20 +3944,13 @@ _GLIBCXX_END_NAMESPACE_CXX11
{ this->resize(__n, _CharT()); }
#if __cplusplus >= 201103L
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
/// A non-binding request to reduce capacity() to size().
void
- shrink_to_fit() _GLIBCXX_NOEXCEPT
- {
-#if __cpp_exceptions
- if (capacity() > size())
- {
- try
- { reserve(0); }
- catch(...)
- { }
- }
-#endif
- }
+ shrink_to_fit() noexcept
+ { reserve(); }
+#pragma GCC diagnostic pop
#endif
/**
@@ -3984,7 +3979,14 @@ _GLIBCXX_END_NAMESPACE_CXX11
* data.
*/
void
- reserve(size_type __res_arg = 0);
+ reserve(size_type __res_arg);
+
+ /// Equivalent to shrink_to_fit().
+#if __cplusplus > 201703L
+ [[deprecated("use shrink_to_fit() instead")]]
+#endif
+ void
+ reserve();
/**
* Erases the string, making it empty.
diff --git a/libstdc++-v3/include/bits/basic_string.tcc b/libstdc++-v3/include/bits/basic_string.tcc
index 75218a40610..a64b63a37fb 100644
--- a/libstdc++-v3/include/bits/basic_string.tcc
+++ b/libstdc++-v3/include/bits/basic_string.tcc
@@ -280,29 +280,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
basic_string<_CharT, _Traits, _Alloc>::
reserve(size_type __res)
{
- // Make sure we don't shrink below the current size.
- if (__res < length())
- __res = length();
-
const size_type __capacity = capacity();
- if (__res != __capacity)
- {
- if (__res > __capacity
- || __res > size_type(_S_local_capacity))
- {
- pointer __tmp = _M_create(__res, __capacity);
- this->_S_copy(__tmp, _M_data(), length() + 1);
- _M_dispose();
- _M_data(__tmp);
- _M_capacity(__res);
- }
- else if (!_M_is_local())
- {
- this->_S_copy(_M_local_data(), _M_data(), length() + 1);
- _M_destroy(__capacity);
- _M_data(_M_local_data());
- }
- }
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2968. Inconsistencies between basic_string reserve and
+ // vector/unordered_map/unordered_set reserve functions
+ // P0966 reserve should not shrink
+ if (__res <= __capacity)
+ return;
+
+ pointer __tmp = _M_create(__res, __capacity);
+ this->_S_copy(__tmp, _M_data(), length() + 1);
+ _M_dispose();
+ _M_data(__tmp);
+ _M_capacity(__res);
}
template<typename _CharT, typename _Traits, typename _Alloc>
@@ -342,6 +332,41 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_set_length(length() - __n);
}
+ template<typename _CharT, typename _Traits, typename _Alloc>
+ void
+ basic_string<_CharT, _Traits, _Alloc>::
+ reserve()
+ {
+ if (_M_is_local())
+ return;
+
+ const size_type __length = length();
+ const size_type __capacity = _M_allocated_capacity;
+
+ if (__length <= size_type(_S_local_capacity))
+ {
+ this->_S_copy(_M_local_data(), _M_data(), __length + 1);
+ _M_destroy(__capacity);
+ _M_data(_M_local_data());
+ }
+#if __cpp_exceptions
+ else if (__length < __capacity)
+ try
+ {
+ pointer __tmp
+ = _Alloc_traits::allocate(_M_get_allocator(), __length + 1);
+ this->_S_copy(__tmp, _M_data(), __length + 1);
+ _M_dispose();
+ _M_data(__tmp);
+ _M_capacity(__length);
+ }
+ catch (const __cxxabiv1::__forced_unwind&)
+ { throw; }
+ catch (...)
+ { /* swallow the exception */ }
+#endif
+ }
+
template<typename _CharT, typename _Traits, typename _Alloc>
void
basic_string<_CharT, _Traits, _Alloc>::
@@ -953,16 +978,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
basic_string<_CharT, _Traits, _Alloc>::
reserve(size_type __res)
{
- if (__res != this->capacity() || _M_rep()->_M_is_shared())
- {
- // Make sure we don't shrink below the current size
- if (__res < this->size())
- __res = this->size();
- const allocator_type __a = get_allocator();
- _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
- _M_rep()->_M_dispose(__a);
- _M_data(__tmp);
- }
+ const size_type __capacity = capacity();
+
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2968. Inconsistencies between basic_string reserve and
+ // vector/unordered_map/unordered_set reserve functions
+ // P0966 reserve should not shrink
+ if (__res <= __capacity)
+ {
+ if (!_M_rep()->_M_is_shared())
+ return;
+
+ // unshare, but keep same capacity
+ __res = __capacity;
+ }
+
+ const allocator_type __a = get_allocator();
+ _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
+ _M_rep()->_M_dispose(__a);
+ _M_data(__tmp);
}
template<typename _CharT, typename _Traits, typename _Alloc>
@@ -1006,7 +1040,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// The standard places no restriction on allocating more memory
// than is strictly needed within this layer at the moment or as
- // requested by an explicit application call to reserve().
+ // requested by an explicit application call to reserve(n).
// Many malloc implementations perform quite poorly when an
// application attempts to allocate memory in a stepwise fashion
@@ -1140,6 +1174,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return *this;
}
+ template<typename _CharT, typename _Traits, typename _Alloc>
+ void
+ basic_string<_CharT, _Traits, _Alloc>::
+ reserve()
+ {
+ if (length() < capacity() || _M_rep()->_M_is_shared())
+ try
+ {
+ const allocator_type __a = get_allocator();
+ _CharT* __tmp = _M_rep()->_M_clone(__a);
+ _M_rep()->_M_dispose(__a);
+ _M_data(__tmp);
+ }
+ catch (const __cxxabiv1::__forced_unwind&)
+ { throw; }
+ catch (...)
+ { /* swallow the exception */ }
+ }
+
template<typename _CharT, typename _Traits, typename _Alloc>
typename basic_string<_CharT, _Traits, _Alloc>::size_type
basic_string<_CharT, _Traits, _Alloc>::
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc
index 02f6bb2629e..a60f2d62da8 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc
@@ -136,13 +136,19 @@ void test01()
sz04 = str02.capacity();
VERIFY( sz04 >= sz03 );
VERIFY( sz04 >= 100 );
+#if __cplusplus <= 201703L
str02.reserve();
- sz03 = str02.capacity();
-#if _GLIBCXX_USE_CXX11_ABI
- VERIFY( sz03 < 100);
#else
- VERIFY( sz03 == 0 );
+ str02.shrink_to_fit(); // reserve is deprecated in C++20
#endif
+ sz03 = str02.capacity();
+ VERIFY( sz03 < sz04 );
+
+ // P0966: reserve should not shrink
+ str02.reserve(100);
+ sz03 = str02.capacity();
+ str02.reserve(sz03 - 1);
+ VERIFY( str02.capacity() == sz03 );
sz03 = str02.size() + 5;
str02.resize(sz03);
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc
index 854c2902e6b..cde253e1142 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc
@@ -33,13 +33,19 @@ void test01()
size_type_s sz02 = str01.capacity();
VERIFY( sz02 >= sz01 );
VERIFY( sz02 >= 100 );
+#if __cplusplus <= 201703L
str01.reserve();
- sz01 = str01.capacity();
-#if _GLIBCXX_USE_CXX11_ABI
- VERIFY( sz01 < 100);
#else
- VERIFY( sz01 == 0 );
+ str01.shrink_to_fit(); // reserve is deprecated in C++20
#endif
+ sz01 = str01.capacity();
+ VERIFY( sz01 < sz02 );
+
+ // P0966: reserve should not shrink
+ str01.reserve(100);
+ sz01 = str01.capacity();
+ str01.reserve(sz01 - 1);
+ VERIFY( str01.capacity() == sz01 );
sz01 = str01.size() + 5;
str01.resize(sz01);
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/18654.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/18654.cc
index e9dbf7f55f6..13f65f57133 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/18654.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/18654.cc
@@ -47,11 +47,17 @@ void test01()
{
string str(i, 'x');
str.reserve(3 * i);
+ const size_type cap = str.capacity();
+ VERIFY( cap >= 3 * i );
str.reserve(2 * i);
- VERIFY( str.capacity() == 2 * i );
+ VERIFY( str.capacity() == cap );
+#if __cplusplus <= 201703L
str.reserve();
+#else
+ str.shrink_to_fit(); // reserve is deprecated in C++20
+#endif
VERIFY( str.capacity() == i );
}
}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/2.cc
index 43ae4c6cd9d..1e87dde6d2e 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/2.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/2.cc
@@ -29,7 +29,11 @@ void test02()
std::string str01 = "twelve chars";
// str01 becomes shared
std::string str02 = str01;
- str01.reserve(1);
+#if __cplusplus <= 201703L
+ str01.reserve();
+#else
+ str01.shrink_to_fit(); // reserve is deprecated in C++20
+#endif
VERIFY( str01.capacity() >= 12 );
}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc
index 436ed59a3b5..fa1584cc134 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc
@@ -33,13 +33,19 @@ void test01()
size_type_s sz02 = str01.capacity();
VERIFY( sz02 >= sz01 );
VERIFY( sz02 >= 100 );
+#if __cplusplus <= 201703L
str01.reserve();
- sz01 = str01.capacity();
-#if _GLIBCXX_USE_CXX11_ABI
- VERIFY( sz01 < 100);
#else
- VERIFY( sz01 == 0 );
+ str01.shrink_to_fit(); // reserve is deprecated in C++20
#endif
+ sz01 = str01.capacity();
+ VERIFY( sz01 < sz02 );
+
+ // P0966: reserve should not shrink
+ str01.reserve(100);
+ sz01 = str01.capacity();
+ str01.reserve(sz01 - 1);
+ VERIFY( str01.capacity() == sz01 );
sz01 = str01.size() + 5;
str01.resize(sz01);
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/18654.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/18654.cc
index 374c27ea43d..fcdcd6abb14 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/18654.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/18654.cc
@@ -47,11 +47,17 @@ void test01()
{
wstring str(i, L'x');
str.reserve(3 * i);
+ const size_type cap = str.capacity();
+ VERIFY( cap >= 3 * i );
str.reserve(2 * i);
- VERIFY( str.capacity() == 2 * i );
+ VERIFY( str.capacity() == cap );
+#if __cplusplus <= 201703L
str.reserve();
+#else
+ str.shrink_to_fit(); // reserve is deprecated in C++20
+#endif
VERIFY( str.capacity() == i );
}
}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/2.cc
index fac8adffcf4..1ec140e61bf 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/2.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/2.cc
@@ -29,7 +29,11 @@ void test02()
std::wstring str01 = L"twelve chars";
// str01 becomes shared
std::wstring str02 = str01;
- str01.reserve(1);
+#if __cplusplus <= 201703L
+ str01.reserve();
+#else
+ str01.shrink_to_fit(); // reserve is deprecated in C++20
+#endif
VERIFY( str01.capacity() == 12 );
}
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