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Merged
merged 1 commit into from
Sep 5, 2025
Merged

[libc++][C++03] cherry-pick #125423 #156824

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22 changes: 15 additions & 7 deletions libcxx/include/__cxx03/string
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Original file line number Diff line number Diff line change
Expand Up @@ -1101,12 +1101,20 @@ public:
_LIBCPP_HIDE_FROM_ABI size_type length() const _NOEXCEPT { return size(); }

_LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
size_type __m = __alloc_traits::max_size(__alloc());
if (__m <= std::numeric_limits<size_type>::max() / 2) {
return __m - __alignment;
if (size_type __m = __alloc_traits::max_size(__alloc()); __m <= std::numeric_limits<size_type>::max() / 2) {
size_type __res = __m - __alignment;

// When the __endian_factor == 2, our string representation assumes that the capacity
// (including the null terminator) is always even, so we have to make sure the lowest bit isn't set when the
// string grows to max_size()
if (__endian_factor == 2)
__res &= ~size_type(1);

// We have to allocate space for the null terminator, but max_size() doesn't include it.
return __res - 1;
} else {
bool __uses_lsb = __endian_factor == 2;
return __uses_lsb ? __m - __alignment : (__m / 2) - __alignment;
return __uses_lsb ? __m - __alignment - 1 : (__m / 2) - __alignment - 1;
}
}

Expand Down Expand Up @@ -1970,11 +1978,11 @@ void basic_string<_CharT, _Traits, _Allocator>::__grow_by_and_replace(
size_type __n_add,
const value_type* __p_new_stuff) {
size_type __ms = max_size();
if (__delta_cap > __ms - __old_cap - 1)
if (__delta_cap > __ms - __old_cap)
__throw_length_error();
pointer __old_p = __get_pointer();
size_type __cap =
__old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms - 1;
__old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms;
__annotate_delete();
auto __allocation = std::__allocate_at_least(__alloc(), __cap + 1);
pointer __p = __allocation.ptr;
Expand Down Expand Up @@ -2017,7 +2025,7 @@ void
__throw_length_error();
pointer __old_p = __get_pointer();
size_type __cap =
__old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms - 1;
__old_cap < __ms / 2 - __alignment ? __recommend(std::max(__old_cap + __delta_cap, 2 * __old_cap)) : __ms;
__annotate_delete();
auto __allocation = std::__allocate_at_least(__alloc(), __cap + 1);
pointer __p = __allocation.ptr;
Expand Down
2 changes: 0 additions & 2 deletions libcxx/test/libcxx-03/strings/basic.string/string.capacity/max_size.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,6 @@
//
//===----------------------------------------------------------------------===//

// XFAIL: FROZEN-CXX03-HEADERS-FIXME

// <string>

// This test ensures that the correct max_size() is returned depending on the platform.
Expand Down
2 changes: 0 additions & 2 deletions libcxx/test/std/strings/basic.string/string.capacity/max_size.pass.cpp
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Expand Up @@ -8,8 +8,6 @@

// UNSUPPORTED: no-exceptions

// XFAIL: FROZEN-CXX03-HEADERS-FIXME

// <string>

// size_type max_size() const; // constexpr since C++20
Expand Down
2 changes: 0 additions & 2 deletions libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer_size.pass.cpp
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Expand Up @@ -6,8 +6,6 @@
//
//===----------------------------------------------------------------------===//

// XFAIL: FROZEN-CXX03-HEADERS-FIXME

// <string>

// basic_string<charT,traits,Allocator>&
Expand Down
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