https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80780
Bug ID: 80780
Summary: Front-end support needed for
experimental::source_location
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
I've just added a partial implementation of <experimental/source_location> to
trunk (r248110).
The missing pieces need some FE help.
1) because the location info returned by source_location::current() should be
the location of the caller the current implementation uses default arguments:
struct source_location
{
// 14.1.2, source_location creation
static constexpr source_location
current(const char* __file = __builtin_FILE(),
const char* __func = __builtin_FUNCTION(),
int __line = __builtin_LINE(),
int __col = 0) noexcept
{
source_location __loc;
__loc._M_file = __file;
__loc._M_func = __func;
__loc._M_line = __line;
__loc._M_col = __col;
return __loc;
}
This works OK, but means the signature of the function doesn't match the one in
the TS (which has no parameters). The standard does allow us to add parameters
with default arguments to member functions, but it might be nice if it wasn't
needed. I'm not sure how best to do that. Maybe make the FE recognise
std::experimental::fundamentals_v2::source_location::current() as magic, so
that location info inside the function uses the location of the caller? Maybe
add a new attribute to perform said magic for any inline function? (If
current() is called indirectly, e.g. through a function pointer, the result is
unspecified so the magic doesn't need to work when the function isn't inlined).
2) source_location::current().function_name() uses __func__ which is not very
descriptive in C++. It would be nice to have a __builtin_PRETTY_FUNCTION to get
a better function name than __builtin_FUNCTION provides.
3) source_location::column().column() always returns zero, because there's no
"__builtin_column" to get a column number, the way __builtin_LINE gives a line
number.
I mistakenly though that calling current() in a default member initializer gave
the wrong locations, but it does the right thing (giving the location of the
constructor body that initializes the member).
