CWG 2631 (https://cplusplus.github.io/CWG/issues/2631.html) reports
an issue on how the default argument is evaluated. this problem is
more obvious when it comes to how `std::source_location::current()`
is evaluated as a default argument. but not all compilers have the
same behavior, see https://godbolt.org/z/PK865KdG4.
notebaly, clang-15 evaluates the default argument at the callee
site. so we need to check the capability of compiler and fall back
to the one defined by util/source_location-compat.hh if the compiler
suffers from CWG 2631. and clang-16 implemented CWG2631 in
https://reviews.llvm.org/D136554. But unfortunately, this change
was not backported to clang-15.
before switching over to clang-16, for using std::source_location::current()
as the default parameter and expect the behavior defined by CWG2631,
we have to use the compatible layer provided by Seastar. otherwise
we always end up having the source_location at the callee side, which
is not interesting under most circumstances.
so in this change, all places using the idiom of passing
std::source_location::current() as the default parameter are changed
to use seastar::compat::source_location::current(). despite that
we have `#include "seastarx.h"` for opening the seastar namespace,
to disambiguate the "namespace compat" defined somewhere in scylladb,
the fully qualified name of
`seastar::compat::source_location::current()` is used.
see also 09a3c63345, where we used
std::source_location as an alias of std::experimental::source_location
if it was available. but this does not apply to the settings of our
current toolchain, where we have GCC-12 and Clang-15.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#14086
82cac8e7cf