[f2py] segmentation fault

Greetings dear f2py users

it is now a week that I am trying to debug my code, and i have not
much ideas left on what's wrong

the code does a seg fault after a few iteration, that means I am
reading/writing outside of where i am supposed to do so.

my fortran variable declaration is okey
my f2py statement is ok

I run f2py with these options:
--debug-capi -DF2PY_REPORT_ATEXIT -DF2PY_REPORT_ON_ARRAY_COPY=1
-DDEBUG_COPY_ND_ARRAY
and the fortran compiler with every debug options -check all -debug
all -diag-enable -C -warn

all the debug and check_and_fix are ok when I call the subroutine from python
the arrays in python are created fortran ordered.

and i still have a seg fault and it's not about accessing a bad array
index in the fortran code

so my question is how can i debug this type of errors?
sometimes, when it runs but segfault on the return from fortran to
python I have a bad pointer allocation message with a memroy address.
How can i use that? how can i have access to the name of what it is
pointing?
I have to say that wrinting/commenting some lines to find out where it
stops change the place of crash in the code.

What can be my tools to find out what is happening?

something came to my mind too. do i have to do a f2py statement for a
local fortran variable which the size depends on a entering parameter?
I'll explain

subroutine toto(n1,n2,toto1)

implicit none
integer*4 :: n1,n2,n3
real*8 :: toto1(n1,n2)
real*8, allocatable :: toto2(:,:)
!f2py integer(4) intend(in),depend(toto1)::n1
!f2py integer(4) intend(in),depend(toto1)::n2
!f2py real(8) dimension(n1,n2) intent(in) :: toto1
!f2py n1=shape(toto1,0)
!f2py n2=shape(toto1,1)

n3= blah
allocate(toto2(n1,n3))

blahblah
return
 end

and in python i have
toto1=numpy.empty([n1,n2], dtype='d',order='FORTRAN')

and i call module.toto(n1,n2,toto1)

So should I replace the 1st f2py line by
!f2py integer(4) intend(in),depend(toto1,toto2)::n1
and add
!f2py n1=shape(toto2,0)


by the way I experimentally figured out that the old fortran
convention to order the variables in calling a subroutine has
sometimes an influence on having some wrapping errors or not
like subroutine toto( integer first, then arrays)

Thanks for any kind of answers or ideas you can have
Cheers
Xavier