Debugging with GDB Manual HP WDB v6.3 (5900-2180, August 2012)

Following commands are used to debug multi-threaded programs:
• 'thread threadno', a command to switch among threads
• 'info threads', a command to inquire about existing threads
• 'thread apply [threadno] [all] args', a command to apply a command to a list
of threads
The GDB thread debugging facility allows you to observe all threads while your program runs―but
whenever GDB takes control, one thread in particular is always the focus of debugging. This thread
is called the current thread. Debugging commands show program information from the perspective
of the current thread.
Whenever GDB detects a new thread in your program, it displays the target system's identification
for the thread with a message in the form '[New systag]'. systag is a thread identifier whose
form varies depending on the particular system. For example, on LynxOS, you might see
[New process 35 thread 27]
when GDB notices a new thread. In contrast, on an SGI system, the systag is simply something
like 'process 368', with no further qualifier.
For debugging purposes, GDB associates its own thread number―always a single integer―with
each thread in your program.
info threads Display a summary of all threads currently in your program. GDB displays for
each thread (in this order):
1. the thread number assigned by GDB
2. the target system's thread identifier (systag)
3. the current stack frame summary for that thread
An asterisk '*' to the left of the GDB thread number indicates the current thread.
For example,
((gdb)) info threads
3 process 35 thread 27 0x34e5 in sigpause ()
2 process 35 thread 23 0x34e5 in sigpause ()
* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
at threadtest.c:68
On HP-UX systems:
For debugging purposes, GDB associates its own thread number―a small integer assigned in
thread-creation order―with each thread in your program.
Whenever GDB detects a new thread in your program, it displays both GDB's thread number and
the target system's identification for the thread with a message in the form '[New systag]'. systag
is a thread identifier whose form varies depending on the particular system. For example, on
HP-UX, you see
[New thread 2 (system thread 26594)]
when GDB notices a new thread.
Here are commands to get more information about threads:
info threads Display a summary of all threads currently in your program.
GDB displays for each thread (in this order):
1. the thread number assigned by GDB
2. the target system's thread identifier (systag)
3. the current stack frame summary for that thread
4. the priority of a thread
An asterisk '*' to the left of the GDB thread number indicates
the current thread.
36 Running Programs Under GDB