gcc-8 adds a new warning controlled by -Wcast-function-type, which is
implied on by Rebirth's default options. This new warning rejects
attempts to reinterpret_cast between function pointer types. While this
might provide some value when the function pointer was derived by taking
the address of a properly declared function provided elsewhere in the
same program, it is wrong when the function pointer is returned by an
external library call, such as GetProcAddress, which always returns a
placeholder type instead of the actual type of the target function.
Switch to using a union with type-punning, which achieves the same
effect as the cast, but does not count as a cast, and therefore does not
provoke the warning.
References: <https://github.com/dxx-rebirth/dxx-rebirth/issues/388>
The Windows exception handler probes the stack to determine how much can
be safely dumped, up to a fixed maximum number of bytes. A logic error
caused the probe function to start its stack probe lower than intended,
so the eventual dump code logs fewer pre-exception bytes than intended.
Fix that error so that the dump shows more pre-exception bytes.
Also, log the address of the ud2 instruction, so that the effective load
address of the module can be determined. Without this, ASLR makes
reading the dumps needlessly difficult.
The dump logger probes for the end of the stack, then rounds down to the
nearest paragraph boundary to simplify the logic in the hexdump routine.
The termination condition in the hexdump code assumed that there would
exist an integer N such that (`start` + (16 * N) == `end`). Since `end`
is rounded to a multiple of 16, this held if and only if `start` is also
a multiple of 16. In practice, this tended to happen, but it was not
guaranteed by the code. If it ever failed to happen, then the hexdump
routine would not terminate and would instead perform an invalid read
beyond the edge of the stack.
Modify the hexdump routine to round `start` to a multiple of 16 so that
the termination condition works as intended. This has the useful side
effect that hex dumps now always start paragraph aligned. When the
stack was not paragraph aligned, this change will cause the hexdump to
show bytes below the stack pointer at the time of the fault. However,
the stack requirements of the handler itself ensure that these bytes
will be valid.
