mirror of
https://github.com/espressif/binutils-gdb.git
synced 2025-06-25 21:41:47 +08:00
06acc08f0a
The overload resolution mechanism assigns badness values to the
necessary conversions to be made on types to pick a champion. A
badness value consists of a "rank" that scores the conversion and a
"subrank" to differentiate conversions of the same kind.
An auxiliary function, 'sum_ranks', is used for adding two badness
values. In all of its uses, except two, 'sum_ranks' is used for
populating the subrank of a badness value. The two exceptions are in
'rank_one_type':
~~~
/* See through references, since we can almost make non-references
references. */
if (TYPE_IS_REFERENCE (arg))
return (sum_ranks (rank_one_type (parm, TYPE_TARGET_TYPE (arg), NULL),
REFERENCE_CONVERSION_BADNESS));
if (TYPE_IS_REFERENCE (parm))
return (sum_ranks (rank_one_type (TYPE_TARGET_TYPE (parm), arg, NULL),
REFERENCE_CONVERSION_BADNESS));
~~~
Here, the result of a recursive call is combined with
REFERENCE_CONVERSION_BADNESS. This leads to the problem of
over-punishment by combining two ranks. Consider this:
void an_overloaded_function (const foo &);
void an_overloaded_function (const foo &&);
...
foo arg;
an_overloaded_function(arg);
When ranking 'an_overloaded_function (const foo &)', the badness
values REFERENCE_CONVERSION_BADNESS and CV_CONVERSION_BADNESS are
combined, whereas 'rank_one_type' assigns only the
REFERENCE_CONVERSION_BADNESS value to 'an_overloaded_function (const
foo &&)' (there is a different execution flow for that). This yields
in GDB picking the latter function as the overload champion instead of
the former.
In fact, the 'rank_one_type' function should have given
'an_overloaded_function (const foo &)' the CV_CONVERSION_BADNESS
value, with the see-through referencing increasing the subrank a
little bit. This can be achieved by introducing a new badness value,
REFERENCE_SEE_THROUGH_BADNESS, which bumps up the subrank only, and
using it in the two "exceptional" cases of 'sum_ranks'.
gdb/ChangeLog:
2019-12-06 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdbtypes.h: Define the REFERENCE_SEE_THROUGH_BADNESS value.
* gdbtypes.c (rank_one_type): Use REFERENCE_SEE_THROUGH_BADNESS
for ranking see-through reference cases.
gdb/testsuite/ChangeLog:
2019-12-06 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdb.cp/rvalue-ref-overload.cc: Add a case that involves both
CV and reference conversion for overload resolution.
* gdb.cp/rvalue-ref-overload.exp: Test it.
Change-Id: I39ae6505ab85ad0bd21915368c82540ceeb3aae9
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.