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The gdb.base/whatis-ptype-typedefs.exp testcase has several tests that
fail on 32-bit architectures. E.g., on 'x86-64 -m32', I see:
...
FAIL: gdb.base/whatis-ptype-typedefs.exp: lang=c: cast: whatis (float_typedef) v_uchar_array_t_struct_typedef (invalid)
FAIL: gdb.base/whatis-ptype-typedefs.exp: lang=c: cast: ptype (float_typedef) v_uchar_array_t_struct_typedef (invalid)
...
gdb.log:
(gdb) whatis (float_typedef) v_uchar_array_t_struct_typedef
type = float_typedef
(gdb) FAIL: gdb.base/whatis-ptype-typedefs.exp: lang=c: cast: whatis (float_typedef) v_uchar_array_t_struct_typedef (invalid)
As Simon explained [1], the issue boils down to the fact that on
64-bit, this is an invalid cast:
(gdb) p (float_typedef) v_uchar_array_t_struct_typedef
Invalid cast.
while on 32 bits it is valid:
(gdb) p (float_typedef) v_uchar_array_t_struct_typedef
$1 = 1.16251721e-41
The expression basically tries to cast an array (which decays to a
pointer) to a float. The cast works on 32 bits because a float and a
pointer are of the same size, and value_cast works in that case:
~~~
More general than a C cast: accepts any two types of the same length,
and if ARG2 is an lvalue it can be cast into anything at all. */
~~~
On 64 bits, they are not the same size, so it ends throwing the
"Invalid cast" error.
The testcase is expecting the invalid cast behavior, thus the FAILs.
A point of these tests was to cover as many code paths in value_cast
as possible, as a sort of documentation of the current behavior:
# The main idea here is testing all the different paths in the
# value casting code in GDB (value_cast), making sure typedefs are
# preserved.
...
# We try all combinations, even those that don't parse, or are
# invalid, to catch the case of a regression making them
# inadvertently valid. For example, these convertions are
# invalid:
...
In that spirit, this commit makes the testcase adjust itself depending
on size of floats and pointers, and also test floats of different
sizes.
Passes cleanly on x86-64 GNU/Linux both -m64/-m32.
[1] - https://sourceware.org/ml/gdb-patches/2017-11/msg00382.html
gdb/ChangeLog:
2017-11-20 Pedro Alves <palves@redhat.com>
* gdb.base/whatis-ptype-typedefs.c (double_typedef)
(long_double_typedef): New typedefs.
Use DEF on double and long double.
* gdb.base/whatis-ptype-typedefs.exp: Add double and long double
cases.
(run_tests): New 'float_ptr_same_size', 'double_ptr_same_size',
and 'long_double_ptr_same_size' locals. Use them to decide
whether cast from array/function to float is valid/invalid.
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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.