In order to reach the middle guard (at m_stack_base + GUARD_OFFSET)
before the bottom guard (at m_stack_base), the stack pointer
must start at an address which is higher than the middle guard.
It also didn't make sense that we were allocating memory
and then not using the top part of it.
If the compiler can detect an issue with a format string at compile
time, then we should take advantage of that and turn the issue into a
hard compile-time error as such problems almost always lead to UB.
This helps with catching logging or assertion messages that have been
converted over to fmt but are still using the old, non-fmt variants
of the logging macros.
This commit also fixes all incorrect usages that I could find.
Fixes https://bugs.dolphin-emu.org/issues/12327.
When we started using fmt in CheckExternalExceptions, JitArm64
mysteriously stopped working even though the code path where
fmt was used never was reached. This is because the compiler
added a function prologue and epilogue to set up the stack,
since the code path that used fmt required the use of the stack.
However, the breakage didn't actually have anything to do
with the usage of the stack in itself, but rather with the
compiler's insertion of a stack canary. In the function
epilogue, a cmp instruction was inserted to check that the
stack canary had not been overwritten during the execution
of the function. This cmp instruction overwriting the status
flags ended up having a disastrous side effect once execution
returned to code emitted by JitArm64::WriteExceptionExit.
JitArm64's dispatcher contains a branch to the "do_timing"
code which is intended to be taken if the PPC downcount is
negative. However, the dispatcher doesn't update the status
flags on its own before this conditional branch, but rather
expects the calling code to have set them as a side effect
of DoDownCount. The root cause of our bug was that
JitArm64::WriteExceptionExit was calling DoDownCount before
Check(External)Exceptions instead of after.
1. Comparing string_views does not behave the same as strncmp
in the case where SConfig's game ID is longer than 6 chars.
2. DTMHeader::GetGameID wasn't excluding null bytes for game IDs
shorter than 6 chars.
3. == was accidentally used instead of !=.
This issue is both severe and surprisingly difficult to find
the root cause of, so I think it would make sense to add a simple
hotfix for now. https://bugs.dolphin-emu.org/issues/12327
Fallback Region
A user-selected fallback to use instead of the default PAL
This is used for unknown region or region free titles to give them
the ability to force region to use. This replaces the current fallback region
of PAL. This can be useful if a user is trying to play a region free
tilte that is originally NTSC and expects to be run at NTSC speeds. This
may be done when a user attempts to dump a WAD of their own without
understanding the settings they have chosen, or could be an intentional
decision by a developer of a ROM hack that can be injected into a
Virtual Console WAD.
Remove using System Menu region being checked in GetFallbackRegion
Use DiscIO::Region instead of std::String for fallback
Add explanation text for Fallback Region
Unfortunately, adding a DEBUG_ASSERT_MSG_FMT isn't actually possible
right now because of compiler bugs:
https://github.com/dolphin-emu/dolphin/pull/9284
We could require a newer version of GCC (10) but that would require
updating GCC on the build machines.
For what it's worth, older versions of GCC (8, 9) are broken in
many ways: adding constexpr to some Matrix functions causes GCC 8
to generate bugged code that causes the Wii IR pointer to disappear,
which means that the generated builds are already unusable
(see https://dolp.in/i12324).
Additionally, we've already had to add workarounds for those versions
in the format macros to fix compilation bugs. This time, it looks like
workarounds won't cut it; even applying the workaround
described in https://github.com/fmtlib/fmt/pull/1580 does not help.
Markus Wick