Re: pointer to function in constructor

From:
Mad Ant <anton.harris@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 22 Aug 2008 01:57:07 -0700 (PDT)
Message-ID:
<915976ea-1e84-4937-a96b-ad9ae0e55025@f63g2000hsf.googlegroups.com>
On Aug 21, 4:49 pm, mlimber <mlim...@gmail.com> wrote:

On Aug 21, 10:29 am, Mad Ant <anton.har...@gmail.com> wrote:

I have to convert a program from C to C++. The original code used
drivers that were available in C, and now are only available in C++.
Thus, I have the "honour" of converting the code.
There are a couple of areas that are blocking me. I've already taken
care of the rest.

I have a structure that is initialized as soon as it is declared in a
variable :
<<
const struct driver_t beirlistener_driver = {
        .name = "beirlistener_driver",
        .cfg_ctl = {
                .cfg_new = &beirlistener_cfg_new,
                .cfg_parse = &beirlistener_cfg_parse,
                .cfg_del = &beirlistener_cfg_del,
                .cfg_parse_ended = &beirlistener_cfg_parse_end
        },
        .ctx_ctl = {
                .ctx_new = &beirlistener_ctx_new,
                .ctx_del = &beirlistener_ctx_del
        },
        .thread_ctl = {
                .run = &beirlistener_run,
                .queue_clean = NULL,
                .stop = &thread_request_stop_intr
        }};

name is, of course, a 'char *'.
cfg_ctl, ctx_ctl and thread_ctl are structures containing pointers to
functions.
The structure contains the necessary functions called to initialize,
un, and destroy/delete a thread. It is used in several different
files, depending on the thread it has to start.

Of course, it would be folly to suppose that it would be accepted as
is in C++. It's not.
The only real solution I could find was to declare a constructor for
the struct (not really elegant, I know), which would receive the
addresses of the functions that are called. So the variable
declaration would be something along the lines of :
<<
const struct driver_t beirlistener_driver = {"beirlistener_driver",
&beirlistener_cfg_new, &beirlistener_cfg_parse, ...};

However, I tried declaring it as such ... :
<<
struct driver_t {
        char * name;
        struct config_ctl_t cfg_ctl;
        struct context_ctl_t ctx_ctl;
        struct thread_ctl_t thread_ctl;

        driver_t(char * cname, int (*fcn)(void **)) {
                name = cname;
                cfg_ctl.cfg_new = fcn;
        }};

... along with the variable declaration as mentioned just above, but
it doesn't work. It doesn't seem to recognize the pointer to a
function in the constructor, since it gives me the following message :
<<
/home/anton/Projects/splusserver3/src/beirlistener.c:90: error: scalar
object =91beirlistener_driver' requires one element in initializer

I've done research, but I con't find a solution to this.
Any help anyone can give me to resolve this is very much appreciated.
Thanks all.


Try:

 const struct driver_t beirlistener_driver = {
        "beirlistener_driver",
        {
                &beirlistener_cfg_new,
                &beirlistener_cfg_parse,
                &beirlistener_cfg_del,
                &beirlistener_cfg_parse_end
        },
        {
                &beirlistener_ctx_new,
                &beirlistener_ctx_del
        },
        {
                &beirlistener_run,
                NULL,
                &thread_request_stop_intr
        }
 };

Cheers! --M


This works perfectly. I can't believe I didn't think of it. *hits
himself on the forehead*

Cheers!

Mad Ant

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