Modifies union construction in the debug directory so output is more
amenable to alternative compilers. Verified that this change produces
code that builds with clang, gcc, msvc, nvhpc, aocc, icc, openxl, and
cray hpc.
These were the kinds of errors seen in MSVC, which this patch fixes.
```
debug/Decoder.hh(24): error C2461: 'gem5::debug::unions::Decoder': constructor syntax missing formal parameters
debug/Decoder.hh(31): error C7624: Type name 'gem5::debug::unions::Decoder' cannot appear on the right side of a class member access expression
```
When an object is a field in a union, it's the programmer's
resposibility to destroy it from the union's destructor. We can simply
neglect to do that and avoid having to use new to create the flags.
Also, we can define the flags as inline variables (a c++17 feature), and
then create a constexpr references to them. This lets us refer to debug
flags in constexpr objects, although we can't interact with them at, for
instance, construciton time or we'd lose our own constexpr-ness since
the actual object is not constexpr.
In c++20 we would hypothetically be able to use constexpr with new and
delete, but there may be additional restrictions that would make this
particular use impossible. Also this avoids leaking memory, which, even
though it's intentional, may confuse tools like valgrind.
Also, we need to ensure that all headers are included in some source
file so that they exist in the final executable, so that they show up in
the help, can be enabled/disabled, etc.
Change-Id: Ia43111d938e7af7140b1c17dd68135f426d0a1e9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49783
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Jui-min Lee <fcrh@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
