Instead of checking for absolute paths and current working directories
in various file system operations, there is one simple solution: allow
overriding `std.fs.cwd` on WASI.
os.realpath is back to causing a compile error when used on WASI. This
caused a compile error in the Sema handling of `@src()`. The compiler
should never call realpath, so the commit that made this change is
reverted (95ab942184427e7c9b840d71f4d093931e3e48fb). If this breaks
debug info, a different strategy is needed to solve it other than using
realpath.
I also removed the preopens code and replaced it with something much
simpler. There is no longer any global state in the standard library.
Additionally-
* os.openat no longer does an unnecessary fstat on WASI when O.WRONLY
is not provided.
* os.chdir is back to causing a compile error on WASI.
`expectEqualBytes` will now truncate the hexdump of each input to a maximum window of 256 bytes, which makes it safe to use for arbitrarily large inputs. Therefore, it can be used in `expectEqualSlices` when the type is u8.
Fixes a regression introduced in
e35f297aeb993ec956ae80379ddf7f86069e109b.
Now there is test coverage for ArrayList.shrinkAndFree in the case when
resizing fails.
Now it can refuse to resize when it would disturb the metadata tracking
strategy, resulting in smaller code size, a simpler implementation, and
less fragmentation.
The previous version had a fatal flaw: it did ensureCapacity(1) on the
freelist when allocating, but I neglected to consider that you could
free() twice in a row. Silly!
This strategy allocates an intrusive freelist node with every
allocation, big or small. It also does not have the problems with resize
because in this case we can push the upper areas of freed stuff into the
corresponding freelist.
Ran into this when using a program that uses CreateFileMapping and then trying to call `std.fs.createFile` on the mapped file. More info can be found here:
https://stackoverflow.com/questions/41844842/when-error-1224-error-user-mapped-file-occurs
Before:
```
error.Unexpected NTSTATUS=0xc0000243
C:\Users\Ryan\Programming\Zig\zig\lib\std\os\windows.zig:138:40: 0x7ff74e957466 in OpenFile (test.exe.obj)
else => return unexpectedStatus(rc),
^
```
After:
```
FAIL (AccessDenied)
C:\Users\Ryan\Programming\Zig\zig\lib\std\os\windows.zig:137:30: 0x7ff7f5b776ea in OpenFile (test.exe.obj)
.USER_MAPPED_FILE => return error.AccessDenied,
^
```
