[issue9919] gdbinit lineno result is one line in excess

[qpatata]

qpatata  added the comment:

I'm sorry, I've not explained correctly.

I'm wondering if the addition of the \n is ok or not, taken into account that 
it breaks the format of the "pyframe" macro output. It could be better to keep 
the older version (without the \n").

Kind regards.

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[issue9919] gdbinit lineno result is one line in excess

[qpatata]

qpatata  added the comment:

Hi,

Thanks for the fix.

I'm wondering if it is valid to add a "\n" in the "lineno" print. This macro is 
called by other ones, like pyframe, that have their own format specifiers.

Kind regards.

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[issue9919] gdbinit lineno result is one line in excess

[qpatata]

qpatata  added the comment:

Well, me also I'm not expert in gdb.

Solution looks nice and previous testcase now gives the correct answer.

Thanks a lot for your help.

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[issue9919] gdbinit lineno result is one line in excess

[qpatata]

qpatata  added the comment:

Hello,

Thanks for your colaboration.

Starting by the following python file, called "prueba.py":

> cat prueba.py
import time

def bar():
time.sleep(10);
print "hello";

def foo():
  while True:
bar();

foo();




Open a gdb session with python2-6 as target:

> gdb /usr/bin/python2.6

and run the python program. 

gdb> run prueba.py

After a few seconds, type Ctrl-C to break the program. Usually, break will 
interrupt it when execution is in the "sleep" statement. A "bt" gives:

#0  0xb7fe2424 in __kernel_vsyscall ()
#1  0xb7d42fdd in select () from /lib/i686/cmov/libc.so.6
#2  0x08119a3f in floatsleep (self=0x0, args=(10,)) at 
../Modules/timemodule.c:918
#3  time_sleep (self=0x0, args=(10,)) at ../Modules/timemodule.c:206
#4  0x080e0721 in call_function (f=Frame 0x82e17ac, for file prueba.py, line 4, 
in bar (), 
throwflag=0) at ../Python/ceval.c:3750
#5  PyEval_EvalFrameEx (f=Frame 0x82e17ac, for file prueba.py, line 4, in bar 
(), throwflag=0)
at ../Python/ceval.c:2412
...

If we go until C frame #5 (up, up, ...) and execute the lineno macro:

#5  PyEval_EvalFrameEx (f=Frame 0x82e17ac, for file prueba.py, line 4, in bar 
(), throwflag=0)
at ../Python/ceval.c:2412
2412in ../Python/ceval.c

(gdb) lineno
5
(gdb) 

It is clear the mismatch between the line reported by lineno (5), the one in 
the source file (4) and the one displayed by gdb (4).

In addition, if we look at the version history of the "gdbinit" file, we can 
see how version 39276 has an implementation of lineno who matches the related C 
code in Python project, but next version (39492) introduces a boolean to 
control the end of loop. This change is, probably, the origen of the mismatch.

Thanks a lot.

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[issue9919] gdbinit lineno result is one line in excess

[qpatata]

New submission from qpatata :

Thanks a lot to all python teams for your excel.lent work.

When latest version of gdbinit macros is used to debug with gdb a python 2.4 
session, the result from lineno macro seems one line more than the correct one.

If we compare the gdb macro:

define lineno
set $__continue = 1
set $__co = f->f_code
set $__lasti = f->f_lasti
set $__sz = ((PyStringObject *)$__co->co_lnotab)->ob_size/2
set $__p = (unsigned char *)((PyStringObject *)$__co->co_lnotab)->ob_sval
set $__li = $__co->co_firstlineno
set $__ad = 0
while ($__sz-1 >= 0 && $__continue)
  set $__sz = $__sz - 1
  set $__ad = $__ad + *$__p
  set $__p = $__p + 1
  if ($__ad > $__lasti)
set $__continue = 0
  end
  set $__li = $__li + *$__p
  set $__p = $__p + 1
end
printf "%d", $__li
end

with the related C source code in libpython.py

def addr2line(self, addrq):
'''
Get the line number for a given bytecode offset

Analogous to PyCode_Addr2Line; translated from pseudocode in
Objects/lnotab_notes.txt
'''
co_lnotab = self.pyop_field('co_lnotab').proxyval(set())

# Initialize lineno to co_firstlineno as per PyCode_Addr2Line
# not 0, as lnotab_notes.txt has it:
lineno = int_from_int(self.field('co_firstlineno'))

addr = 0
for addr_incr, line_incr in zip(co_lnotab[::2], co_lnotab[1::2]):
addr += ord(addr_incr)
if addr > addrq:
return lineno
lineno += ord(line_incr)
return lineno

we see that if addr  is greater than addrq, the python codes returns 
immedialty, but the gdb macro adds a new delta of lines before exit the loop.

Kind regards.

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messages: 117133
nosy: qpatata
priority: normal
severity: normal
status: open
title: gdbinit lineno result is one line in excess
type: behavior
versions: Python 2.5

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