Binutils with MCST patches
53ba833325
Consider the following declaration:
type Small is new Integer range 0 .. 2 ** 4 - 1;
type Simple_Array is array (1 .. 4) of Small;
pragma Pack (Simple_Array);
SA : Simple_Array := (1, 2, 3, 4);
Trying to change the value of one of the elements in the packed array
causes the debugger to crash:
(gdb) set sa(3) := 9
[1] 4880 segmentation fault gdb -q foo
The circumstances leading to the crash are as follow:
. ada_evaluate_subexp creates a value corresponding to "sa(3)".
. ada_evaluate_subexp then tries to assign 9 to this value, and
for this calls value_assign (via ada_value_assign).
. Because the array is packed, the destination value is 3 bits long,
and as a result, value_assign uses the parent to determine that
element byte address and offset:
| if (value_bitsize (toval))
| {
| struct value *parent = value_parent (toval);
|
| changed_addr = value_address (parent) + value_offset (toval);
The destination value (corresponding to "sa(3)") was incorrectly created
by ada-lang.c:ada_value_primitive_packed_val, because the "parent" was
left as NULL. So, when we try to dereference it to get the parent address,
GDB crashed.
The first part of the fix therefore consists in setting that field.
This required the addition of a new "setter" in value.[hc]. It fixes
the crash, but is still not sufficient for the assignment to actually
work.
The second part of the problem came from the fact that value_assign
seems to expect the "child"'s address to be equal to the parent's address,
with the difference being the offset. Unfortunately, this requirement was
not followed by ada_value_primitive_packed_val, so the second part of
the fix consisted in fixing that.
Still, this was not sufficient, because it caused a regression when
trying to perform an aggregate assignment of a packed array of packed
record. The key element here is the nesting of packed entities.
Looking at the way ada_value_primitive_packed_val creates the value
of each sub-component, one can see that the value's offset is set
to the offset compared to the start of the parent. This was meant to
match what value_primitive_field does as well.
So, with our array of records, if the record offset was 2, and if
the field we're interested in that record is at offset 1, the record
value's offset would be set to 2, and the field value's offset would
be set to 1. But the address for both values would be left to the
array's address. This is where things start breaking down, because
the value_address function for our field value would return the
address of the array + 1, instead of + 3.
This is what causes the final issue, here, because ada-lang.c's
value_assign_to_component needs to compute the offset of the
subcomponent compared to the top-level aggregate's start address
(the array in our case). And it does so by subtracting the array's
address from the sub-component's address. When you have two levels
of packed components, and the mid-level component is at an offset of
the top-level component, things didn't work, because the component's
address was miscomputed (the parent's offset is missing).
The fix consists is fixing value_address to match the work done by
value_primitive_field (where we ignore the parent's offset).
gdb/ChangeLog:
* value.h (set_value_parent): Add declaration.
* value.c (set_value_parent): New function.
(value_address): If VALUE->PARENT is not NULL, then use it as
the base address instead of VALUE->LOCATION.address.
* ada-lang.c (ada_value_primitive_packed_val): Keep V's address
the same as OBJ's address. Adjust V's offset accordingly.
Set V's parent.
gdb/testsuite/ChangeLog:
* gdb.ada/set_pckd_arr_elt: New testcase.
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| bfd | ||
| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| .cvsignore | ||
| .gitignore | ||
| 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 | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release | ||
| symlink-tree | ||
| 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.