After discussion (starting there:
https://github.com/gbdev/rgbds/pull/594#issuecomment-706437458
), it was decided that plain nested macros should not be
allowed.
Since #590 is fixed, EQUS can be used as a workaround;
multiline strings (#589) will make that easier on the
user when implemented.
Fixes#588, supersedes and closes#594.
Additionally, closes#388.
The old "find symbol with auto scope" function is now three:
- One finds the exact name passed to it, skipping any checks
This is useful e.g. if such checks were already performed.
- One checks that the name is not scoped, and calls the first.
This is useful for names that cannot be scoped, such as checking for EQUS.
Doing this instead of the third should improve performance somehwat, since
this specific case is hit by the lexer each time an identifier is read.
- The last one checks if the name should be expanded (`.loc` → `Glob.loc`),
and that the local part is not scoped. This is essentially the old function.
Use C11 standard _Noreturn instead of attributes (except, of course, MSVC)
Remove unused helpers
Avoid trapping in release builds, in favor of just unreachability
Improve shim when __builtin_* are not available
When a user tried to overwrite a builtin symbol, it would change its
type despite the error, making the second try succeed. This is
problematic, as the location of a builtin symbol cannot be updated.
Since the lexer buffer wraps, the refilling gets handled in two steps:
First, iff the buffer would wrap, the buffer is refilled until its end.
Then, if more characters are requested, that amount is refilled too.
An important detail is that `read()` may not return as many characters as
requested; for this reason, the first step checks if its `read()` was
"full", and skips the second step otherwise.
This is also where a bug lied.
After a *lot* of trying, I eventually managed to reproduce the bug on an
OpenBSD VM, and after adding a couple of `assert`s in `peekInternal`, this
is what happened, starting at line 724:
0. `lexerState->nbChars` is 0, `lexerState->index` is 19;
1. We end up with `target` = 42, and `writeIndex` = 19;
2. 42 + 19 is greater than `LEXER_BUF_SIZE` (= 42), so the `if` is entered;
3. Within the first `readChars`, **`read` only returns 16 bytes**,
advancing `writeIndex` to 35 and `target` to 26;
4. Within the second `readChars`, a `read(26)` is issued, overflowing the
buffer.
The bug should be clear now: **the check at line 750 failed to work!** Why?
Because `readChars` modifies `writeIndex`.
The fix is simply to cache the number of characters expected, and use that.
