The copy constructor descends into 128 levels before it finishes a value
without the call stack, so the iterative path is otherwise only reached
by the few tests that nest deeper than that.
JSON_NO_THREAD_LOCAL switches the descent off, which sends every value
down that path. Running the whole test suite that way covers it with
every object type, string type, allocator, and base class the suite
already exercises. The new ci_test_no_thread_local target does that; the
macro had no build coverage at all before.
Copying a nested value also has to carry over what the element-wise copy
constructor would have copied: the parents that JSON_DIAGNOSTICS relies
on, and the positions that JSON_DIAGNOSTIC_POSITIONS reports. Both are
now checked on either side of the descent bound, for objects and arrays.
Neither was tested before, and dropping either one makes the new tests
fail.
Also quantify what JSON_NO_THREAD_LOCAL costs a copy instead of calling
it "measurably slower".
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The diagnostic position of a string value was derived by subtracting the
parsed value's length from the end position. Escape sequences make the
source token longer than the value it parses to, so the reported start
position landed inside the string, one byte off per escape sequence:
input: {"a":"\n\n\n\n\n\n"}
start_pos() == 11, so the reported range covered n\n\n\n"
instead of the documented "\n\n\n\n\n\n"
This contradicts the documented behavior of start_pos(), which is the
position of the opening quote, and it also corrupted the "(bytes N-M)"
part of JSON_DIAGNOSTICS exception messages. Strings with multi-byte
UTF-8 but no escapes were unaffected, which is why this went unnoticed.
Record the offset of the token in the lexer when it starts scanning and
use that, instead of reconstructing it from the parsed value. Booleans,
null and numbers already reported correct positions and are unchanged.
The new lexer member and accessor are compiled only when
JSON_DIAGNOSTIC_POSITIONS is enabled, which is already part of the ABI
tag, so the default build is unaffected.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann
Harinath NampallyandGitHub