Ada Tasks - Debugging with GDB
Description: Debugging with GDB

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##### 15.4.9.5 Extensions for Ada Tasks

Support for Ada tasks is analogous to that for threads (see Threads). gdb provides the following task-related commands:

`info tasks`
  This command shows a list of current Ada tasks, as in the following example:

                (gdb) info tasks
                  ID       TID P-ID Pri State                 Name
                   1   8088000   0   15 Child Activation Wait main_task
                   2   80a4000   1   15 Accept Statement      b
                   3   809a800   1   15 Child Activation Wait a
                *  4   80ae800   3   15 Runnable              c

  In this listing, the asterisk before the last task indicates it to be the task currently being inspected.

  ID
    Represents gdb's internal task number.
  TID
    The Ada task ID.
  P-ID
    The parent's task ID (gdb's internal task number).
  Pri
    The base priority of the task.
  State
    Current state of the task.
    `Unactivated`
      The task has been created but has not been activated. It cannot be executing.
    `Runnable`
      The task is not blocked for any reason known to Ada. (It may be waiting for a mutex, though.) It is conceptually "executing" in normal mode.
    `Terminated`
      The task is terminated, in the sense of ARM 9.3 (5). Any dependents that were waiting on terminate alternatives have been awakened and have terminated themselves.
    `Child Activation Wait`
      The task is waiting for created tasks to complete activation.
    `Accept Statement`
      The task is waiting on an accept or selective wait statement.
    `Waiting on entry call`
      The task is waiting on an entry call.
    `Async Select Wait`
      The task is waiting to start the abortable part of an asynchronous select statement.
    `Delay Sleep`
      The task is waiting on a select statement with only a delay alternative open.
    `Child Termination Wait`
      The task is sleeping having completed a master within itself, and is waiting for the tasks dependent on that master to become terminated or waiting on a terminate Phase.
    `Wait Child in Term Alt`
      The task is sleeping waiting for tasks on terminate alternatives to finish terminating.
    `Accepting RV with` taskno
      The task is accepting a rendez-vous with the task taskno.
  Name
    Name of the task in the program.

`info task` taskno
  This command shows detailled informations on the specified task, as in the following example:

                (gdb) info tasks
                  ID       TID P-ID Pri State                  Name
                   1   8077880    0  15 Child Activation Wait  main_task
                *  2   807c468    1  15 Runnable               task_1
                (gdb) info task 2
                Ada Task: 0x807c468
                Name: task_1
                Thread: 0x807f378
                Parent: 1 (main_task)
                Base Priority: 15
                State: Runnable

`task`
  This command prints the ID of the current task.

                (gdb) info tasks
                  ID       TID P-ID Pri State                  Name
                   1   8077870    0  15 Child Activation Wait  main_task
                *  2   807c458    1  15 Runnable               t
                (gdb) task
                [Current task is 2]

`task` taskno
  This command is like the `thread` threadno command (see Threads). It switches the context of debugging from the current task to the given task.

                (gdb) info tasks
                  ID       TID P-ID Pri State                  Name
                   1   8077870    0  15 Child Activation Wait  main_task
                *  2   807c458    1  15 Runnable               t
                (gdb) task 1
                [Switching to task 1]
                #0  0x8067726 in pthread_cond_wait ()
                (gdb) bt
                #0  0x8067726 in pthread_cond_wait ()
                #1  0x8056714 in system.os_interface.pthread_cond_wait ()
                #2  0x805cb63 in system.task_primitives.operations.sleep ()
                #3  0x806153e in system.tasking.stages.activate_tasks ()
                #4  0x804aacc in un () at un.adb:5

`break` linespec`task` taskno
`break` linespec`task` taskno`if ...`
  These commands are like the `break ... thread ...` command (see Thread Stops). linespec specifies source lines, as described in Specify Location.

  Use the qualifier ‘`task taskno`’ with a breakpoint command to specify that you only want gdb to stop the program when a particular Ada task reaches this breakpoint. taskno is one of the numeric task identifiers assigned by gdb, shown in the first column of the ‘`info tasks`’ display.

  If you do not specify ‘`task taskno`’ when you set a breakpoint, the breakpoint applies to all tasks of your program.

  You can use the `task` qualifier on conditional breakpoints as well; in this case, place ‘`task taskno`’ before the breakpoint condition (before the `if`).

  For example,

                (gdb) info tasks
                  ID       TID P-ID Pri State                 Name
                   1 140022020   0   15 Child Activation Wait main_task
                   2 140045060   1   15 Accept/Select Wait    t2
                   3 140044840   1   15 Runnable              t1
                *  4 140056040   1   15 Runnable              t3
                (gdb) b 15 task 2
                Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
                (gdb) cont
                Continuing.
                task # 1 running
                task # 2 running

                Breakpoint 5, test_task_debug () at test_task_debug.adb:15
                15               flush;
                (gdb) info tasks
                  ID       TID P-ID Pri State                 Name
                   1 140022020   0   15 Child Activation Wait main_task
                *  2 140045060   1   15 Runnable              t2
                   3 140044840   1   15 Runnable              t1
                   4 140056040   1   15 Delay Sleep           t3