Thread-Specific Breakpoints (Debugging with GDB)

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#### 5.5.4 Thread-Specific Breakpoints

When your program has multiple threads (see Debugging Programs with Multiple Threads), you can choose whether to set breakpoints on all threads, or on a particular thread.

`break locspec thread thread-id`
`break locspec thread thread-id if …`

  locspec specifies a code location or locations in your program. See Location Specifications, for details.

  Use the qualifier ‘`thread thread-id`’ with a breakpoint command to specify that you only want GDB to stop the program when a particular thread reaches this breakpoint. The thread-id specifier is one of the thread identifiers assigned by GDB, shown in the first column of the ‘`info threads`’ display.

  If you do not specify ‘`thread thread-id`’ when you set a breakpoint, the breakpoint applies to all threads of your program.

  You can use the `thread` qualifier on conditional breakpoints as well; in this case, place ‘`thread thread-id`’ before or after the breakpoint condition, like this:

      (gdb) break frik.c:13 thread 28 if bartab > lim

Thread-specific breakpoints are automatically deleted when GDB detects the corresponding thread is no longer in the thread list. For example:

    (gdb) c
    Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.

There are several ways for a thread to disappear, such as a regular thread exit, but also when you detach from the process with the `detach` command (see Debugging an Already-running Process), or if GDB loses the remote connection (see Remote Debugging), etc. Note that with some targets, GDB is only able to detect a thread has exited when the user explicitly asks for the thread list with the `info threads` command.

A breakpoint can’t be both thread-specific and inferior-specific (see Inferior-Specific Breakpoints), or task-specific (see Ada Tasks); using more than one of the `thread`, `inferior`, or `task` keywords when creating a breakpoint will give an error.

Next: Interrupted System Calls, Previous: Background Execution, Up: Thread Stops [Contents][Index]