GNU UPC

Multiple Posix Threads

Pthreads implementation is another variant of GCC UPC run-time where each thread is mapped into pthreads instead of Unix processes. Pthreads run-time does not use UPC threads start-up synchronization.

Compile Options

-g -O0
-dwarf-2-upc
-fupc-pthreads-model-tls

Debugging Options

set pagination off
set target-async on
set detach-on-fork off
set non-stop on

Sample Debugging Session

Compile example code (static or dynamic thread allocation can be used):

$ upc -fupc-threads-4 -fupc-pthreads-model-tls -g -O0 -dwarf-2-upc \
    -o upc-example upc-example.upc

Create GDB's startup file .gdbinitin the current directory with the following content:

set pagination off
set target-async on
set detach-on-fork off
set non-stop on

Note: You may choose to create some other file instead of .gdbinit. In this case you will need to run GDB UPC with "-x your-startup-file" option.
Note: GDB UPC upcstartgate option is not necessary as one thread GCC UPC run-time does not uses thread synchronization mechanism.

Specify UPC Debugging Assistant shared library for GCC UPC compiler:

csh shell:
$ setenv UDA_GUPC_PLUGIN_LIBRARY [...]/plugin/uda-plugin.so

bash shell:
$ UDA_GUPC_PLUGIN_LIBRARY=[...]/plugin/uda-plugin.so
$ export UDA_GUPC_PLUGIN_LIBRAR

Make sure that GDB on your path is indeed GDB UPC. For example:

$ gdb -v
GNU gdb (GDB) 7.1.50.2 20100918 (GDB UPC/dev)
Copyright (C) 2010 Free Software Foundation, Inc.
[...]
For bug reporting instructions, please see:
[...]

At this point you can start your debugging session.

$ gdb upc_example
[...]
(gdb) b upc_main
Breakpoint 1 at 0x4016cd: file upc-example.upc, line 23.
(gdb) r
[Thread debugging using libthread_db enabled]
upc_lang: using GUPC plugin.
[New UPC Thread 0]
[New UPC Thread 1]
[New UPC Thread 2]
[New UPC Thread 3]

Breakpoint 1, main () at upc-example.upc:23
23        if (!MYTHREAD)
Current language:· auto
The current source language is "auto; currently upc".
Breakpoint 1, main () at upc-example.upc:23
23        if (!MYTHREAD)
Breakpoint 1, main () at upc-example.upc:23
23        if (!MYTHREAD)
Breakpoint 1, main () at upc-example.upc:23
23       if (!MYTHREAD)
Starting program: /eng/upc/dev/nenad/GDB UPC-dev/examples/upc-example 
Breakpoint 1, main () at upc-example.upc:23
23       if (!MYTHREAD)
Current language:· auto
The current source language is "auto; currently upc".
(gdb)

At this point all of the UPC threads are running, however as GDB UPC is still in the GDB mode, all threads report a breakpoint event.· Execute upc-sync command to switch debugging into the UPC mode.

(gdb) upc-sync
UPC Mode activated.
(gdb-upc) info threads
  3 UPC Thread 3· main () at upc-example.upc:23
  2 UPC Thread 2· main () at upc-example.upc:23
  1 UPC Thread 1· main () at upc-example.upc:23
* 0 UPC Thread 0· main () at upc-example.upc:23
(gdb-upc)

Continue debugging of your program.