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xo-expression2: DUniqueSring: fix copy during hypothetical GC

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This commit is contained in:
Roland Conybeare 2026-01-16 20:47:54 -05:00
commit 33c4e2dc0a
2 changed files with 21 additions and 5 deletions
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8
include/xo/expression2/DUniqueString.hpp
View file

@ -59,6 +59,10 @@ namespace xo {
/** @defgroup duniquestring-methods methods **/
///@{
/** Available storage for this instance.
* For completeness' sake since uniquestring not modifiable
**/
size_type capacity() const noexcept { return _text()->capacity(); }
size_type size() const noexcept { return _text()->size(); }
const char * chars() const noexcept { return _text()->chars(); }
@ -74,6 +78,8 @@ namespace xo {
std::size_t hash() const noexcept { return _text()->hash(); }
operator std::string_view() const noexcept { return std::string_view(*_text()); }
/** not assignable **/
DUniqueString & operator=(const DUniqueString &) = delete;
///@}
/** @defgroup duniquestring-printable-methods printable facet methods **/
@ -105,7 +111,7 @@ namespace xo {
/** DString containing actual string content immediately follows DUniqueString
* in memory; part of same alloc
**/
const DString * _text() const noexcept;
DString * _text() const noexcept;
//explicit DUniqueString(const DString * text) : text_{text} {}

18
src/expression2/DUniqueString.cpp
View file

@ -6,13 +6,14 @@
#include "DUniqueString.hpp"
#include <xo/arena/padding.hpp>
#include <xo/indentlog/scope.hpp>
#include <cstring>
namespace xo {
using xo::mm::padding;
using xo::facet::typeseq;
namespace scm {
const DString *
DString *
DUniqueString::_text() const noexcept
{
// location of paired DString is chosen
@ -30,7 +31,7 @@ namespace xo {
size_t offset = padding::with_padding(sizeof(*this));
assert(offset > 0);
return (const DString *)(((std::byte *)this) + offset);
return (DString *)(((std::byte *)this) + offset);
}
bool
@ -84,8 +85,17 @@ namespace xo {
DUniqueString * copy = (DUniqueString *)mm.alloc_copy((std::byte *)this);
if (copy)
*copy = *this;
if (copy) {
// Copy assignment not implemented in general
// *copy = *this;
// in this case *copy already has the same size as *this
assert(size() <= capacity());
strncpy(copy->_text()->data(),
this->_text()->chars(),
this->size());
}
return copy;
}