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Recover from parse errors when parse_error() returns true (#3989)

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The return value of json_sax::parse_error() was documented both as "must
return false" and as "whether the parsing should continue", and the code
just passed it on. For JSON text, parsing stopped anyway, but sax_parse()
could report success for invalid input. The binary readers read on after
the error, looping forever on a CBOR indefinite-length array without its
end.

Now false stops parsing, and true recovers from the error:

- JSON text is repaired with the smallest local edit (insert a missing
  ',' or ':', remove a stray token, keep the readable part of a broken
  string or number, null for a value that cannot be read, close the
  innermost container at a wrong closing bracket and all of them at the
  end of the input), and parsing continues. The SAX events stay balanced,
  every key is followed by exactly one value, and each token is reported
  at most once.
- The binary formats cannot resynchronize, so they stop, but complete
  the value read so far.

sax_parse() returns false after any error. parse(), accept(), and the
from_*() functions never recover and compile to the same code as before.

Supersedes #4522.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-27 20:16:42 +02:00
parent 509c07041f
commit 9adb510a0d
21 changed files with 4242 additions and 285 deletions
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include/nlohmann/detail/input/binary_reader.hpp
+97 -79
View File
@@ -188,8 +188,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(current != char_traits<char_type>::eof()))
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(110, chars_read,
exception_message(input_format, concat("expected end of input; last byte: 0x", get_token_string()), "value"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(110, chars_read,
exception_message(input_format, concat("expected end of input; last byte: 0x", get_token_string()), "value"), nullptr));
}
}
@@ -295,8 +295,8 @@ class binary_reader
{
if (JSON_HEDLEY_UNLIKELY(document_size < 0 || static_cast<std::size_t>(document_size) != chars_read - document_start))
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
exception_message(input_format_t::bson, concat("document size ", std::to_string(document_size), " does not match the number of bytes read (", std::to_string(chars_read - document_start), ")"), "document"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
exception_message(input_format_t::bson, concat("document size ", std::to_string(document_size), " does not match the number of bytes read (", std::to_string(chars_read - document_start), ")"), "document"), nullptr));
}
return true;
}
@@ -490,8 +490,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(len < 1))
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bson, concat("string length must be at least 1, is ", std::to_string(len)), "string"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bson, concat("string length must be at least 1, is ", std::to_string(len)), "string"), nullptr));
}
if (JSON_HEDLEY_UNLIKELY(!get_string(input_format_t::bson, len - static_cast<NumberType>(1), result)))
@@ -502,10 +502,10 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(get() != 0x00))
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bson,
"BSON string is not null-terminated",
"string"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bson,
"BSON string is not null-terminated",
"string"), nullptr));
}
return true;
@@ -526,8 +526,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(len < 0))
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bson, concat("byte array length cannot be negative, is ", std::to_string(len)), "binary"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bson, concat("byte array length cannot be negative, is ", std::to_string(len)), "binary"), nullptr));
}
// All BSON binary values have a subtype
@@ -620,8 +620,8 @@ class binary_reader
std::array<char, 3> cr{{}};
static_cast<void>((std::snprintf)(cr.data(), cr.size(), "%.2hhX", static_cast<unsigned char>(element_type))); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
const std::string cr_str{cr.data()};
return sax->parse_error(element_type_parse_position, cr_str,
parse_error::create(114, element_type_parse_position, concat("Unsupported BSON record type 0x", cr_str), nullptr));
return report_error(element_type_parse_position, cr_str,
parse_error::create(114, element_type_parse_position, concat("Unsupported BSON record type 0x", cr_str), nullptr));
}
}
}
@@ -641,9 +641,9 @@ class binary_reader
const auto max_val = static_cast<NumberType>((std::numeric_limits<number_integer_t>::max)());
if (number > max_val)
{
return sax->parse_error(chars_read, get_token_string(),
parse_error::create(112, chars_read,
exception_message(input_format_t::cbor, "negative integer overflow", "value"), nullptr));
return report_error(chars_read, get_token_string(),
parse_error::create(112, chars_read,
exception_message(input_format_t::cbor, "negative integer overflow", "value"), nullptr));
}
return sax->number_integer(static_cast<number_integer_t>(-1) - static_cast<number_integer_t>(number));
}
@@ -978,8 +978,8 @@ class binary_reader
case cbor_tag_handler_t::error:
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::cbor, concat("invalid byte: 0x", last_token), "value"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::cbor, concat("invalid byte: 0x", last_token), "value"), nullptr));
}
case cbor_tag_handler_t::ignore:
@@ -1177,8 +1177,8 @@ class binary_reader
default: // anything else (0xFF is handled inside the other types)
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::cbor, concat("invalid byte: 0x", last_token), "value"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::cbor, concat("invalid byte: 0x", last_token), "value"), nullptr));
}
}
}
@@ -1257,8 +1257,8 @@ class binary_reader
default:
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format_t::cbor, concat("expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x", last_token), "string"), nullptr));
return report_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format_t::cbor, concat("expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0x", last_token), "string"), nullptr));
}
}
}
@@ -1402,8 +1402,8 @@ class binary_reader
default:
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format_t::cbor, concat("expected length specification (0x40-0x5B) or indefinite binary array type (0x5F); last byte: 0x", last_token), "binary"), nullptr));
return report_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format_t::cbor, concat("expected length specification (0x40-0x5B) or indefinite binary array type (0x5F); last byte: 0x", last_token), "binary"), nullptr));
}
}
}
@@ -1483,8 +1483,8 @@ class binary_reader
{
if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::size_t>(len) || len == detail::unknown_size()))
{
return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format_t::cbor, concat("excessive ", context, " size"), "size"), nullptr));
return report_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format_t::cbor, concat("excessive ", context, " size"), "size"), nullptr));
}
result = conditional_static_cast<std::size_t>(len);
return true;
@@ -1980,8 +1980,8 @@ class binary_reader
default: // anything else
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::msgpack, concat("invalid byte: 0x", last_token), "value"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::msgpack, concat("invalid byte: 0x", last_token), "value"), nullptr));
}
}
}
@@ -2063,8 +2063,8 @@ class binary_reader
default:
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format_t::msgpack, concat("expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0x", last_token), "string"), nullptr));
return report_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format_t::msgpack, concat("expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0x", last_token), "string"), nullptr));
}
}
}
@@ -2381,8 +2381,8 @@ class binary_reader
{
if (JSON_HEDLEY_UNLIKELY(len < 0))
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "string length must not be negative", "string"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "string length must not be negative", "string"), nullptr));
}
return true;
}
@@ -2493,7 +2493,7 @@ class binary_reader
{
message = "expected length type specification (U, i, u, I, m, l, M, L); last byte: 0x" + last_token;
}
return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read, exception_message(input_format, message, "string"), nullptr));
return report_error(chars_read, last_token, parse_error::create(113, chars_read, exception_message(input_format, message, "string"), nullptr));
}
/*!
@@ -2594,8 +2594,8 @@ class binary_reader
}
if (number < 0)
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
}
result = static_cast<std::size_t>(number); // NOLINT(bugprone-signed-char-misuse,cert-str34-c): number is not a char
return true;
@@ -2610,8 +2610,8 @@ class binary_reader
}
if (number < 0)
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
}
result = static_cast<std::size_t>(number);
return true;
@@ -2626,8 +2626,8 @@ class binary_reader
}
if (number < 0)
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
}
result = static_cast<std::size_t>(number);
return true;
@@ -2642,13 +2642,13 @@ class binary_reader
}
if (number < 0)
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
exception_message(input_format, "count in an optimized container must be positive", "size"), nullptr));
}
if (!value_in_range_of<std::size_t>(number))
{
return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format, "integer value overflow", "size"), nullptr));
return report_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format, "integer value overflow", "size"), nullptr));
}
result = static_cast<std::size_t>(number);
return true;
@@ -2697,8 +2697,8 @@ class binary_reader
}
if (!value_in_range_of<std::size_t>(number))
{
return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format, "integer value overflow", "size"), nullptr));
return report_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format, "integer value overflow", "size"), nullptr));
}
result = detail::conditional_static_cast<std::size_t>(number);
return true;
@@ -2712,7 +2712,7 @@ class binary_reader
}
if (is_ndarray) // ndarray dimensional vector can only contain integers and cannot embed another array
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read, exception_message(input_format, "ndarray dimensional vector is not allowed", "size"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(113, chars_read, exception_message(input_format, "ndarray dimensional vector is not allowed", "size"), nullptr));
}
std::vector<size_t> dim;
if (JSON_HEDLEY_UNLIKELY(!get_ubjson_ndarray_size(dim)))
@@ -2748,13 +2748,13 @@ class binary_reader
// as modular arithmetic can produce any value, not just 0 or SIZE_MAX.
if (JSON_HEDLEY_UNLIKELY(i > 0 && result > (std::numeric_limits<std::size_t>::max)() / i))
{
return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
return report_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
}
result *= i;
// Additional post-multiplication check to catch any edge cases the pre-check might miss
if (result == 0 || result == npos)
{
return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
return report_error(chars_read, get_token_string(), out_of_range::create(408, exception_message(input_format, "excessive ndarray size caused overflow", "size"), nullptr));
}
if (JSON_HEDLEY_UNLIKELY(!sax->number_unsigned(static_cast<number_unsigned_t>(i))))
{
@@ -2782,7 +2782,7 @@ class binary_reader
{
message = "expected length type specification (U, i, u, I, m, l, M, L) after '#'; last byte: 0x" + last_token;
}
return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read, exception_message(input_format, message, "size"), nullptr));
return report_error(chars_read, last_token, parse_error::create(113, chars_read, exception_message(input_format, message, "size"), nullptr));
}
/*!
@@ -2816,8 +2816,8 @@ class binary_reader
&& JSON_HEDLEY_UNLIKELY(std::binary_search(bjd_optimized_type_markers.begin(), bjd_optimized_type_markers.end(), result.second)))
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, concat("marker 0x", last_token, " is not a permitted optimized array type"), "type"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, concat("marker 0x", last_token, " is not a permitted optimized array type"), "type"), nullptr));
}
if (JSON_HEDLEY_UNLIKELY(!unexpect_eof(input_format, "type")))
@@ -2833,8 +2833,8 @@ class binary_reader
return false;
}
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, concat("expected '#' after type information; last byte: 0x", last_token), "size"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, concat("expected '#' after type information; last byte: 0x", last_token), "size"), nullptr));
}
const bool is_error = get_ubjson_size_value(result.first, is_ndarray);
@@ -2853,8 +2853,8 @@ class binary_reader
const bool is_error = get_ubjson_size_value(result.first, is_ndarray);
if (input_format == input_format_t::bjdata && is_ndarray && !inside_ndarray)
{
return sax->parse_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
exception_message(input_format, "ndarray requires both type and size", "size"), nullptr));
return report_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
exception_message(input_format, "ndarray requires both type and size", "size"), nullptr));
}
return is_error;
}
@@ -3030,8 +3030,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(current > 127))
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format, concat("byte after 'C' must be in range 0x00..0x7F; last byte: 0x", last_token), "char"), nullptr));
return report_error(chars_read, last_token, parse_error::create(113, chars_read,
exception_message(input_format, concat("byte after 'C' must be in range 0x00..0x7F; last byte: 0x", last_token), "char"), nullptr));
}
string_t s(1, static_cast<typename string_t::value_type>(current));
return sax->string(s);
@@ -3053,7 +3053,7 @@ class binary_reader
break;
}
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read, exception_message(input_format, "invalid byte: 0x" + last_token, "value"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read, exception_message(input_format, "invalid byte: 0x" + last_token, "value"), nullptr));
}
/*!
@@ -3081,8 +3081,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(it == bjd_types_map.end() || it->first != size_and_type.second))
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, "invalid byte: 0x" + last_token, "type"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, "invalid byte: 0x" + last_token, "type"), nullptr));
}
string_t type = it->second; // sax->string() takes a reference
@@ -3129,8 +3129,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY((size_and_type.second == 'Z' || size_and_type.second == 'T' || size_and_type.second == 'F')
&& size_and_type.first > max_valueless_container_size))
{
return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format, "excessive array size", "size"), nullptr));
return report_error(chars_read, get_token_string(), out_of_range::create(408,
exception_message(input_format, "excessive array size", "size"), nullptr));
}
if (JSON_HEDLEY_UNLIKELY(!enter_array(size_and_type.first, size_and_type.second)))
@@ -3166,8 +3166,8 @@ class binary_reader
if (input_format == input_format_t::bjdata && size_and_type.first != npos && (size_and_type.second & (1 << 8)) != 0)
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, "BJData object does not support ND-array size in optimized format", "object"), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format, "BJData object does not support ND-array size in optimized format", "object"), nullptr));
}
if (size_and_type.first != npos)
@@ -3215,8 +3215,8 @@ class binary_reader
if (JSON_HEDLEY_UNLIKELY(result_remainder != token_type::end_of_input))
{
return sax->parse_error(chars_read, number_string, parse_error::create(115, chars_read,
exception_message(input_format, concat("invalid number text: ", number_lexer.get_token_string()), "high-precision number"), nullptr));
return report_error(chars_read, number_string, parse_error::create(115, chars_read,
exception_message(input_format, concat("invalid number text: ", number_lexer.get_token_string()), "high-precision number"), nullptr));
}
switch (result_number)
@@ -3230,7 +3230,7 @@ class binary_reader
const auto parsed_float = number_lexer.get_number_float();
if (JSON_HEDLEY_UNLIKELY(!std::isfinite(parsed_float)))
{
return sax->parse_error(
return report_error(
chars_read,
number_string,
out_of_range::create(406, concat("number overflow parsing '", number_string, '\''), nullptr));
@@ -3255,8 +3255,8 @@ class binary_reader
case token_type::end_of_input:
case token_type::literal_or_value:
default:
return sax->parse_error(chars_read, number_string, parse_error::create(115, chars_read,
exception_message(input_format, concat("invalid number text: ", number_lexer.get_token_string()), "high-precision number"), nullptr));
return report_error(chars_read, number_string, parse_error::create(115, chars_read,
exception_message(input_format, concat("invalid number text: ", number_lexer.get_token_string()), "high-precision number"), nullptr));
}
}
@@ -3324,8 +3324,8 @@ class binary_reader
bool bon8_error(const std::string& detail, const char* context)
{
auto last_token = get_token_string();
return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bon8, concat(detail, ": 0x", last_token), context), nullptr));
return report_error(chars_read, last_token, parse_error::create(112, chars_read,
exception_message(input_format_t::bon8, concat(detail, ": 0x", last_token), context), nullptr));
}
/*!
@@ -3839,8 +3839,7 @@ class binary_reader
{
// in case of failure, advance position by 1 to report the failing location
++chars_read;
sax->parse_error(chars_read, "<end of file>", parse_error::create(110, chars_read, exception_message(format, "unexpected end of input", context), nullptr));
return false;
return report_error(chars_read, "<end of file>", parse_error::create(110, chars_read, exception_message(format, "unexpected end of input", context), nullptr));
}
return true;
}
@@ -3952,9 +3951,9 @@ class binary_reader
// (which would defeat allow_exceptions=false / strict discarding).
if (JSON_HEDLEY_UNLIKELY(!is_valid_utf8(result, old_size)))
{
return sax->parse_error(chars_read, get_token_string(),
parse_error::create(113, chars_read,
exception_message(format, "invalid string: ill-formed UTF-8 byte", "string"), nullptr));
return report_error(chars_read, get_token_string(),
parse_error::create(113, chars_read,
exception_message(format, "invalid string: ill-formed UTF-8 byte", "string"), nullptr));
}
return true;
@@ -4041,6 +4040,25 @@ class binary_reader
return true;
}
/*!
@brief report an error to the SAX parser
The binary formats cannot recover from an error: a value's size is given
before its payload, and every byte value is a valid type marker, so after
an error there is no way to find where the next value begins. Reading
therefore stops, whatever the SAX parser's parse_error() returns. That the
SAX parser may ask for the containers read so far to be closed is handled
by @ref json_sax_salvager, not here (see #3989).
@return false, so that the caller stops reading
*/
template<typename Exception>
bool report_error(const std::size_t position, const std::string& last_token, const Exception& ex) const
{
static_cast<void>(sax->parse_error(position, last_token, ex));
return false;
}
/*!
@param[in] format the current format (for diagnostics)
@param[in] context further context information (for diagnostics)
@@ -4051,8 +4069,8 @@ class binary_reader
{
if (JSON_HEDLEY_UNLIKELY(current == char_traits<char_type>::eof()))
{
return sax->parse_error(chars_read, "<end of file>",
parse_error::create(110, chars_read, exception_message(format, "unexpected end of input", context), nullptr));
return report_error(chars_read, "<end of file>",
parse_error::create(110, chars_read, exception_message(format, "unexpected end of input", context), nullptr));
}
return true;
}