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fix string corruption in string_impl::shrink_to_fit #1177

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Merged
grisumbras merged 1 commit into from
Jul 23, 2026
Merged

fix string corruption in string_impl::shrink_to_fit #1177

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4 changes: 2 additions & 2 deletions include/boost/json/detail/impl/string_impl.ipp
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Original file line number Diff line number Diff line change
Expand Up @@ -435,9 +435,9 @@ shrink_to_fit(
auto const t = p_.t;
if(t->size <= sbo_chars_)
{
s_.k = short_string_;
std::memcpy(
s_.buf, data(), t->size);
s_.k = short_string_;
s_.buf[sbo_chars_] =
static_cast<char>(
sbo_chars_ - t->size);
Expand All @@ -458,7 +458,7 @@ shrink_to_fit(
std::memcpy(
tmp.data(),
data(),
size());
size() + 1);
destroy(sp);
*this = tmp;
#ifndef BOOST_NO_EXCEPTIONS
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18 changes: 18 additions & 0 deletions test/string.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1367,6 +1367,24 @@ class string_test

s.shrink_to_fit();
BOOST_TEST(s.capacity() < cap);

std::string const copy( s.begin(), s.end() );

std::size_t const sbo_capacity = string{}.capacity();
std::size_t n = sbo_capacity + 1;
BOOST_ASSERT(s.capacity() > n);
s.resize(n);
s.shrink_to_fit();
BOOST_TEST(s.size() == n);
BOOST_TEST(s == string_view(copy.data(), n));
BOOST_TEST(s.data()[s.size()] == '\0');

n = sbo_capacity - 1;
s.resize(n);
s.shrink_to_fit();
BOOST_TEST(s.size() == n);
BOOST_TEST(s.capacity() == sbo_capacity);
BOOST_TEST(s == string_view(copy.data(), n));
});
}

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