[parted-devel] Parted on GNU Hurd based systems

[Jim Meyering]

"Debarshi 'Rishi' Ray" <debarshi.ray at gmail.com> wrote:
>> Have you considered keeping just the 3-argument sig-handlers
>> and writing a one-argument stub handler for each that merely
>> calls the 3-argument one (with a NULL 2nd arg).
>
> Although it looked to be an elegant solution at first, I now realize
> that it might create some complications on systems where 'sigaction'
> is present but 'SA_SIGINFO' is not (like Hurd); or where 'sigaction'
> itself is missing.
>
> Due to the following block and a similar one in init_ui, the 'struct
> sigaction' variables are only instantiated and assigned when
> SA_SIGINFO is present in signal.h.
> #ifdef SA_SIGINFO
> static struct sigaction    sig_segv;
> static struct sigaction    sig_int;
> static struct sigaction    sig_fpe;
> static struct sigaction    sig_ill;
> #endif /* SA_SIGINFO */
>
> Since the mere presence of 'sigaction' does not offset the absence of
> 'SA_SIGINFO' and we are stuck with one parameter handlers, the latter
> is used as the defining entity. Moreover we do not have to separately
> consider cases where 'sigaction' itself is absent. If there is no
> 'sigaction', then there is no 'SA_SIGINFO' as well.

It's easy to handle the absence of sigaction.
Add this at the top:

#ifndef HAVE_SIGACTION
# define sigaction(a,b,c) /* empty */
#endif

> When the one-argument stub calls the three-argument handler, we would
> basically check whether the second parameter is NULL and act
> accordingly. To avoid a compile time error on Hurd-like kernels we
> would need to insert #ifdef...#else...#endif blocks in the
> three-argument handler so that the mention of 'sigaction' and 'struct
> sigaction' variables do not throw an error.
>
> The argument that the #ifdef...#endif block be removed and 'struct
> sigaction' variables be declared in all cases, so that insertion of
> #ifdef...#else...#endif blocks are not necessary in the three-argument
> handler is flawed because this will not take into consideration cases
> where 'sigaction' itself is absent.
>
>> That would avoid a lot of the duplication.
>
> I feel this duplication is a price we can pay for a clearer code.

No!  Duplication makes maintenance harder.
It becomes too easy to change one copy but not the others.

> Having the control flow from a stub handler to the other; the checking
> of the second parameter; the insertion of #ifdef...#else...#endif in
> the three parameter handlers will reduce the readability.

Shouldn't need any new #ifdefs.

Thanks for persevering.