Michael Haggerty <mhagger@xxxxxxxxxxxx> writes:
> What if we go in the direction not of less infrastructure, but a little
> bit more? Like
>
> struct result {
> int code;
> struct strbuf msg;
> };
>
> int report_errors(struct result *result)
> {
> int code = result->code;
> if (code) {
> error(result->msg.buf);
> }
> result->code = 0;
> strbuf_release(result->msg);
> return code; /* or alternatively (code ? -1 : 0) */
> }
>
> int report_warnings(struct result *result)
> {
> ...
> }
>
> int report_with_prefix(struct result *result, const char *fmt, ...)
> {
> ...
> }
>
> Then a caller could look pretty much like before:
>
> struct result result = RESULT_INIT;
>
> if (some_func(fd, &result))
> return report_errors(&result);
>
> Other callers might not even bother to check the return value of the
> function, relying instead on result.code via process_error():
>
> char *ptr = some_func(fd, &result);
> if (report_errors(&result))
> return -1;
>
> If the result code is considered superfluous, we could use naked strbufs
> and use msg.len as the indicator that there was an error.
Two potential issues are:
- Callers that ignore errors need to actively ignore errors with
strbuf_release(&result.msg);
- Callers have to remember that once the report_errors() function
is called on a "struct result", the struct loses its information.
Neither is insurmountable, but the latter might turn out to be
cumbersome to work around in some codepaths.
Other than that, I think it is OK.
Another alternative may be to have the reporting storage on the side
of the callee, and have callers that are interested in errors to
supply a place to store a pointer to it, i.e.
int some_func(..., struct result **errors) {
static struct result mine;
clear_result(&mine);
... do its thing ...
if (... error detected ...) {
mine.code = E_SOMEFUNC;
strbuf_addstr(&mine.msg, "some_func: foobared");
}
if (errors)
*errors = &mine;
return mine.code;
}
And a caller would do this instead:
struct result *result = NULL;
if (some_func(fd, &result))
return report_errors(result);
where report_errors() and friends will only peek but not clear the
result reporting storage. The clear_result() helper would trivially
be:
void clear_result(struct result *result) {
result->code = 0;
strbuf_release(&result->msg);
}
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