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Fix value(json_pointer, default) aborting under JSON_NOEXCEPTION

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With exceptions disabled (JSON_NOEXCEPTION or -fno-exceptions),
value(const json_pointer&, default) called std::abort() for array
reference tokens that array_index() rejects with out_of_range.404/410:
indices too large to fit size_type, the empty token ("/"), and tokens
like "/1a". With exceptions enabled, the same tokens correctly yielded
the default value, because get_checked_or_null() relied on
JSON_TRY/JSON_INTERNAL_CATCH (detail::out_of_range&) to turn the
exception into nullptr; under JSON_NOEXCEPTION, JSON_THROW aborts
before that catch is ever reached.

get_checked_or_null() now detects those out-of-range tokens itself,
the same way contains(json_pointer) already does (#5495), and only
calls array_index() for tokens that must still raise parse_error.106
or parse_error.109 (e.g. "/01", "/+1"), matching the documented
behavior of value().

Added regression tests to tests/src/unit-disabled_exceptions.cpp
(built with JSON_NOEXCEPTION and -fno-exceptions) and the matching
checks to tests/src/unit-element_access2.cpp for normal exception
mode.

Fixes #5672.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-29 23:41:00 +02:00
parent 633de8e44b
commit 57890cebad
4 changed files with 66 additions and 16 deletions
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single_include/nlohmann/json.hpp
+18 -8
View File
@@ -19520,19 +19520,29 @@ class json_pointer
return nullptr;
}
// may throw parse_error.106/109 for a malformed index; an
// index that is syntactically valid but cannot be
// represented (out_of_range.404/410) is treated like an
// out-of-range index below
typename BasicJsonType::size_type idx{};
JSON_TRY
// tokens that array_index() rejects with parse_error.106/109
// are passed on to it; all other tokens that it would reject
// with out_of_range.404/410 are detected here, so that this
// also works without exceptions
if (JSON_HEDLEY_UNLIKELY(reference_token.size() > 1 && !(reference_token[0] >= '1' && reference_token[0] <= '9')))
{
idx = array_index<BasicJsonType>(reference_token);
static_cast<void>(array_index<BasicJsonType>(reference_token)); // throws parse_error.106/109
}
JSON_INTERNAL_CATCH (detail::out_of_range&)
if (JSON_HEDLEY_UNLIKELY(reference_token.empty() || !std::all_of(reference_token.begin(), reference_token.end(), [](const char c)
{
return c >= '0' && c <= '9';
})))
{
return nullptr;
}
errno = 0; // strtoull() does not reset errno on success
char* p_end = nullptr; // NOLINT(misc-const-correctness)
const unsigned long long magnitude = std::strtoull(reference_token.data(), &p_end, 10); // NOLINT(runtime/int)
if (JSON_HEDLEY_UNLIKELY(errno == ERANGE || magnitude >= static_cast<unsigned long long>((std::numeric_limits<typename BasicJsonType::size_type>::max)()))) // NOLINT(runtime/int)
{
return nullptr;
}
const auto idx = static_cast<typename BasicJsonType::size_type>(magnitude);
if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
{