76136aeda5
A recent change in the compiler highlighted a small weakness in
the function reading the contents of the Ada Task Control Block
(ATCB -- the data that allows us to inspect Ada tasks). As a result,
anytime we read it, we started getting some warnings. For instance,
using the gdb.ada/tasks.exp testcase...
$ gnatmake -g foo.adb
$ gdb foo
(gdb) b foo.adb:60
Breakpoint 1 at 0x403e07: file foo.adb, line 60.
(gdb) run
[...]
Thread 1 "foo" hit Breakpoint 1, foo () at foo.adb:60
60 for J in Task_List'Range loop -- STOP_HERE
... we can see that the "info tasks" command produces some warnings,
followed by the correct output.
(gdb) info tasks
!! -> warning: array or string index out of range
!! -> warning: array or string index out of range
!! -> warning: array or string index out of range
!! -> warning: array or string index out of range
ID TID P-ID Pri State Name
* 1 654050 48 Runnable main_task
2 654ef0 1 48 Accept or Select Term task_list(1)
3 658680 1 48 Accept or Select Term task_list(2)
4 65be10 1 48 Accept or Select Term task_list(3)
The problem comes from the fact that read_atcb, the function responsible
for loading the contents of the ATCB, blindly tries to read some data
which is only relevant when a task is waiting for another task on
an entry call. A comment in that code's section gives a hint as to
how the information is meant to be decoded:
/* Let My_ATCB be the Ada task control block of a task calling the
entry of another task; then the Task_Id of the called task is
in My_ATCB.Entry_Calls (My_ATCB.ATC_Nesting_Level).Called_Task. */
What the comment shows is that, to get the Id of the task being called,
one has to go through the entry calls field, which is an array pointer.
Up to now, we were lucky that, for tasks that are _not_ waiting on an
entry call, its ATCB atc_nesting_level used to be set to 1, and so
we were able to silently read some irrelevant data. But a recent change
now causes this field to be zero instead, and this triggers the warning,
since we are now trying to read outside of the array's range (arrays
in Ada often start at index 1, as is the case here).
We avoid this issue by simply only reading that data when the data
is actually known to be relevant (state == Entry_Caller_Sleep).
This, in turn, allows us to simplify a bit the use of the task_info->state
field, where we no longer need to check task the task has a state equal
to Entry_Caller_Sleep before using this field. Indeed, with this new
approach, we now know that, unless task_info->state == Entry_Caller_Sleep,
the state is now guaranteed to be zero. In other words, we no longer set
task_info->called_task to some random value, forcing to check the task's
state first as a way to verify that the data is not random.
gdb/ChangeLog:
* ada-lang.c (read_atcb): Only set task_info->called_task if
task_info->state == Entry_Caller_Sleep.
(print_ada_task_info): Do not check task_info->state before
checking task_info->called_task.
(info_task): Likewise.
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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.