When we flush a FILE, we behave differently depending on whether we reading from
the file or writing to it:
* If we're writing, we actually write out the buffered data.
* If we're reading, we just drop the buffered (read ahead) data.
After flushing, there should be no additional buffered state stdio keeps about a
FILE, compared to what is true about the underlying file. This includes file
position (offset). When flushing writes, this is taken care of automatically,
but dropping the buffer is not enough to achieve that when reading. This commit
fixes that by seeking back explicitly in that case.
One way the problem manifested itself was upon fseek(SEEK_CUR) calls, as the
position of the underlying file was oftentimes different to the logical position
of the FILE. Since FILE::seek() already calls FILE::flush() prior to actually
modifying the position, fixing FILE::flush() to sync the positions is enough to
fix that issue.
Previously, `fopen()` didn't contain an implementation for the
append modes, even though the Kernel supports it via `O_APPEND`.
This patch rectifies that by implementing them so an assert is
no longer thrown.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
Long ago, there was a fourth stdio default stream, stddbg, connected to the
debug console. It has since been replaced by the dbgputstr() and dbgputch()
syscalls.
3fce2fb205
Remove the last remains of stddbg, as fd 3 is soon going to be reused for socket
takeover.
When using the bounded string operations (e.g. snprintf), the null
terminator was always being written even if there was no space for
it (or indeed any valid buffer at all)
This overwriting caused segmentation faults and memory corruption
Furthermore, fread() has already handled EOF, so there's no need to do
it again. If we read a character, return it, otherwise return EOF.
Note that EOF means "EOF or error" here.
The "stddbg" stream was a cute idea but we never ended up using it in
practice, so let's simplify this and implement userspace dbgprintf() on top
of a simple dbgputch() syscall instead.
This makes debugging LibC startup a little bit easier. :^)
