Gecko:Debugging Tools

.gdbinit

bz's gdbinit

GDB pretty printers

JS-specific printers

General gecko printers

Printing arrays

define ptarray
       if $argc == 0
               help ptarray
       else
               set $size = $arg0.mHdr->mLength
               set $capacity = $arg0.mHdr->mCapacity
               set $size_max = $size - 1
               set $elts = $arg0.Elements()
       end
       if $argc == 1
               set $i = 0
               while $i < $size
                       printf "elem[%u]: ", $i
                       p *($elts + $i)
                       set $i++
               end
       end
       if $argc == 2
               set $idx = $arg1
               if $idx < 0 || $idx > $size_max
                       printf "idx1, idx2 are not in acceptable range: [0..%u].\n", $size_max
               else
                       printf "elem[%u]: ", $idx
                       p *($elts + $idx)
               end
       end
       if $argc == 3
         set $start_idx = $arg1
         set $stop_idx = $arg2
         if $start_idx > $stop_idx
           set $tmp_idx = $start_idx
           set $start_idx = $stop_idx
           set $stop_idx = $tmp_idx
         end
         if $start_idx < 0 || $stop_idx < 0 || $start_idx > $size_max || $stop_idx > $size_max
           printf "idx1, idx2 are not in acceptable range: [0..%u].\n", $size_max
         else
           set $i = $start_idx
               while $i <= $stop_idx
                       printf "elem[%u]: ", $i
                       p *($elts + $i)
                       set $i++
               end
         end
       end
       if $argc > 0
               printf "nsTArray length = %u\n", $size
               printf "nsTArray capacity = %u\n", $capacity
               printf "Element "
               whatis *$elts
       end
end

Chris Jones' handy ptarray command

Frame Tree Dump

<bz> for a frame dump, you can use the layout debugger, or... if you're in a debugger and want to examine the tree, you can do

def frametree
  call nsFrame::DumpFrameTree($arg0)
end

<bz> That should work when called on any nsIFrame to dump the tree it belongs to

Printing nsIAtoms

def pa
  set $atom = $arg0
  if (sizeof(*((&*$atom)->mString)) == 2)
    pu (&*$atom)->mString
  end
end

Reflow Logs

See [Debugging Frame Reflow]

Printing strings

# Define a "ps" command to display subclasses of nsAC?String.  Note that
# this assumes strings as of Gecko 1.9 (well, and probably a few
# releases before that as well); going back far enough will get you
# to string classes that this function doesn't work for.
def ps
  set $str = $arg0
  if (sizeof(*$str.mData) == 1 && ($str.mFlags & 1) != 0)
    print $str.mData
  else
    pu $str.mData $str.mLength
  end
end

# Define a "pu" command to display PRUnichar * strings (100 chars max)
# Also allows an optional argument for how many chars to print as long as
# it's less than 100.
def pu
 set $uni = $arg0
 if $argc == 2
   set $limit = $arg1
   if $limit > 100
     set $limit = 100
   end
 else
   set $limit = 100
 end
 # scratch array with space for 100 chars plus null terminator.  Make
 # sure to not use ' ' as the char so this copy/pastes well.
 set $scratch = "____________________________________________________________________________________________________"
 set $i = 0
 set $scratch_idx = 0
 while (*$uni && $i++ < $limit)
   if (*$uni < 0x80)
     set $scratch[$scratch_idx++] = *(char*)$uni++
   else
     if ($scratch_idx > 0)

set $scratch[$scratch_idx] = '\0' print $scratch set $scratch_idx = 0

     end
     print /x *(short*)$uni++
   end
 end
 if ($scratch_idx > 0)
   set $scratch[$scratch_idx] = '\0'
   print $scratch
 end
end

Dumping the JS Stack

def js
  call DumpJSStack()
end