Weird segfault when parsing a map in a sequence in some cases

[leoetlino]

The following document causes ryml to simply crash when parsing:

- 'a': 1
  b: 2

These ones work, though:

- a: 1
  b: 2

- b: 2
  'a': 1

- b: 2
  'a': 1
  c: 3

'a': 1
b: 2

b: 2
'a': 1

Using the inline flow style for the map in the problematic document also works:

- {'a': 1, b: 2}

It looks like something goes wrong when parsing a map in a sequence, but only if the first key-value pair has a quoted key, and only if the map uses the block style.

[leoetlino]

Looks like the problem is that the indentation is mistakenly set to 4 rather than 2 from _handle_seq_impl:

rapidyaml/src/c4/yml/parse.cpp

Lines 609 to 629 in e1216d4

	if(_scan_scalar(&s)) // this also progresses the line
	{
	_c4dbgp("it's a scalar");
	rem = m_state->line_contents.rem;
	size_t skip = 0;
	if(rem.begins_with(' '))
	{
	_c4dbgp("skipping whitespace...");
	skip = rem.first_not_of(' ');
	_line_progressed(skip);
	rem = rem.sub(skip);
	}
	if(rem.begins_with(": ") || rem.ends_with(':'))
	{
	_c4dbgp("actually, the scalar is the first key of a map, and it opens a new scope");
	addrem_flags(RNXT, RVAL); // before _push_level! This prepares the current level for popping by setting it to RNXT
	_push_level();
	_start_map();
	_store_scalar(s);
	_save_indentation(/*behind*/s.len + skip);

It appears that _save_indentation is being called with the length of the unquoted scalar.

[biojppm]

That's it, you nailed it.