The modification to the grammar in the comment is in line with the
grammar in the zig-spec repo.
Note: checking if the previous token is a colon is insufficent to tell
if a block has a label, the identifier must be checked for as well. This
can be seen in sentinel terminated slicing: `foo[0..1:{}]`
In order to update the printed progress string the code tried to move
the cursor N cells to the left, where N is the number of written bytes,
and then clear the remaining part of the line.
This strategy has two main issues:
- Is only valid if the number of characters is equal to the number of
written bytes,
- Is only valid if the line doesn't get too long.
The second point is the main motivation for this change, when the line
becomes too long the terminal wraps it to a new physical line. This
means that moving the cursor to the left won't be enough anymore as once
the left border is reached it cannot move anymore.
The wrapped line is still stored by the terminal as a single line,
despite now taking more than a single one when displayed. If you try to
resize the terminal you'll notice how the contents are reflowed and are
essentially illegible.
Querying the cursor position on non-Windows systems (plot twist,
Microsoft suggests using VT escape sequences on newer systems) is
extremely cumbersome so let's do something different.
Before printing anything let's save the cursor position and clear the
screen below the cursor, this way we ensure there's absolutely no trace
of stale data on screen, and after the message is printed we simply
restore it.
Given a pointer operand `ptr` and a signed integer operand `idx`
`ptr + idx` and `idx + ptr` -> ptr + @bitCast(usize, @intCast(isize, idx))
`ptr - idx` -> ptr - @bitCast(usize, @intCast(isize, idx))
Thanks @LemonBoy for pointing out that we can take advantage of wraparound
to dramatically simplify the code.
Clang docs say:
> Like -MMD, but also implies -E and writes to stdout by default.
Previously, Zig handled this option by forwarding it directly to Clang,
and disabling depfiles. However this did not adhere to Clang's documented
behavior of these flags.
Now, in addition to being forwarded directly to Clang, `-MM` also
sets c_out_mode = .preprocessor, just like `-E`.
Another issue I noticed is that Zig did not recognize the aliases for
-MG, -MM, or -MMD. The aliases are now recognized.
The presence of ZIG_VERBOSE_LINK now enables --verbose-link.
The presence of ZIG_VERBOSE_CC now enables --verbose-cc.
These are useful when debugging usage of `zig cc` which does not have
CLI flags for these options, since they are not valid C compiler flags.
