Marc Nieper-Wißkirchen wrote:
> gl_list_iterator_t i = gl_list_iterator (list);
> struct foo *elt;
> while (gl_list_iterator_next (, (const void **) , NULL))
> ++elt->bar;
This cast is dangerous: It silences the warning "passing argument 2 of
'gl_list_iterator_next' from incompatible pointer
Hi Ben,
> I've found a few macros for casts useful over years. PSPP uses
> CONST_CAST and UP_CAST from the file below quite a bit:
> https://git.savannah.gnu.org/cgit/pspp.git/tree/src/libpspp/cast.h
That's pointing to a nice solution to the problem that casts don't warn in C.
I use to write
Ben Pfaff wrote:
> I've found a few macros for casts useful over years. PSPP uses
> CONST_CAST and UP_CAST from the file below quite a bit:
> https://git.savannah.gnu.org/cgit/pspp.git/tree/src/libpspp/cast.h
Other projects may want to use these macros as well.
That would make a great
CCing Bruno because of his involvement with the Gnulib list modules.
Disallowing NULL list elements could break existing code that actually uses
them but returning elements with type void * instead of const void * would
be much less incompatible. Code can trivially be ported to such an updated
On Tue, Apr 6, 2021 at 12:18 AM Marc Nieper-Wißkirchen
wrote:
> I have been wondering whether it makes sense to add a small utility trying to
> make typecasts in C as type-safe as possible.
I've found a few macros for casts useful over years. PSPP uses
CONST_CAST and UP_CAST from the file below
On 4/6/21 12:13 PM, Marc Nieper-Wißkirchen wrote:
gl_list_iterator_next has to return two things: An element (represented by
a const void *) and a boolean value. As elements may be NULL
Ah, OK, then that's the problem. The API shouldn't allow null elements.
They're not that useful anyway. If
Hi Paul,
thanks!
By the way, the snippet you gave is not portable C code, as it assumes
> that 'void *' and 'struct foo *' have the same machine representation.
> This is not necessarily true on (admittedly now-rare) machines that have
> different flavors of pointers. I suspect the main problem
On 4/6/21 12:18 AM, Marc Nieper-Wißkirchen wrote:
So what I have in mind are macros that do a type conversion from A to B and
that signal an error on modern compilers if the input is not of type A. For
this, the C11 construct _Generic can be used.
Not sure it's worth the aggravation. Most of
Hi,
I have been wondering whether it makes sense to add a small utility trying
to make typecasts in C as type-safe as possible.
The problem is that typecasts are sometimes unavoidable. For an example,
let's take a look at the following snippet using Gnulib's xlist module:
struct foo
{
int
