30ab358668
It is not currently possible to cast some values to an rvaule
reference. This happens when simple scalar values are cast to an
rvalue reference of the same type, e.g.:
int global_var;
Then in GDB:
(gdb) p static_cast<int&&> (global_var)
Attempt to take address of value not located in memory.
Which is clearly silly.
The problem is that as part of the cast an intermediate value is
created within GDB that becomes an lval_none rather than the original
lval_memory. The casting logic basically goes like this:
The call tree that leads to the error looks like this:
value_cast
value_cast
value_ref
value_addr
error
The first value_cast call is casting the value for 'global_var' to
type 'int&&'. GDB spots that the target type is a reference, and so
calls value_cast again, this time casting 'global_var' to type 'int'.
We then call value_ref to convert the result of the second value_cast
into a reference.
Unfortunately, the second cast results in the value (for global_var)
changing from an lval_memory to an lval_none. This is because int to
int casting calls extract_unsigned_integer and then
value_from_longest.
In theory value_cast has a check at its head that should help in this
case, the code is:
if (value_type (arg2) == type)
return arg2;
However, this only works in some cases. In our case
'value_type (arg2)' will be an objfile owned type, while the type from
the expression parser 'int&&' will be gdbarch owned. The pointers
will not be equal, but the meaning of the type will be equal.
I did consider making the int to int casting case smarter, but this
obviously is only one example. We must also consider things like
float to float, or pointer to pointer....
So, I instead decided to try and make the initial check smarter.
Instead of a straight pointer comparison, I now propose that we use
types_deeply_equal. If this is true then we are casting something
back to its current type, in which case we can preserve the lval
setting by using value_copy.
gdb/ChangeLog:
* valops.c (value_cast): Call value_deeply_equal before performing
any cast.
gdb/testsuite/ChangeLog:
* gdb.cp/rvalue-ref-params.cc (f3): New function.
(f4): New function.
(global_int): New global variable.
(global_float): Likeiwse.
(main): Call both new functions.
* gdb.cp/rvalue-ref-params.exp: Add new tests.
|
||
|---|---|---|
| bfd | ||
| binutils | ||
| config | ||
| contrib | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gdbserver | ||
| gdbsupport | ||
| gnulib | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libctf | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| zlib | ||
| .cvsignore | ||
| .gitattributes | ||
| .gitignore | ||
| ar-lib | ||
| ChangeLog | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| COPYING.LIB | ||
| COPYING.LIBGLOSS | ||
| COPYING.NEWLIB | ||
| depcomp | ||
| djunpack.bat | ||
| install-sh | ||
| libtool.m4 | ||
| lt~obsolete.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| makefile.vms | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| multilib.am | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release.sh | ||
| symlink-tree | ||
| test-driver | ||
| ylwrap | ||
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.