02.04.2020 11:55, Markus Armbruster wrote:
Peter Maydell <peter.mayd...@linaro.org> writes:
On Thu, 2 Apr 2020 at 07:11, Vladimir Sementsov-Ogievskiy
<vsement...@virtuozzo.com> wrote:
Somehow, in general, especially with long function names and long parameter
lists I prefer
ret = func(..);
if (ret < 0) {
return ret;
}
Personally I prefer the other approach -- this one has an extra line
in the source and
needs an extra local variable.
Me too, except when func(...) is so long that
if (func(...) < 0) {
becomes illegible like
if (func(... yadda, yadda,
yadda, ...) < 0) {
Then an extra variable can improve things.
Are you sure that adding a lot of boolean functions is a good idea? I somehow
feel better with more usual int functions with -errno on failure.
Bool is a good return value for functions which are boolean by nature: checks,
is something correspond to some criteria. But for reporting an error I'd prefer
-errno.
When would we want to return an errno? I thought the whole point of the
Error* was that that was where information about the error was returned.
If all your callsites are just going to do "if (ret < 0) { ... } then having
the functions pick an errno value to return is just extra work.
0/-1 vs. true/false is a matter of convention. Lacking convention, it's
a matter of taste. >
0/-1 vs. 0/-errno depends on the function and its callers. When -errno
enables callers to distinguish failures in a sane and simple way, use
it. When -errno feels "natural", I'd say feel free to use it even when
all existing callers only check < 0.
When you return non-null/null or true/false on success/error, neglecting
to document that in a function contract can perhaps be tolerated; you're
using the return type the common, obvious way. But when you return 0/-1
or 0/-errno, please spell it out. I've seen too many "Operation not
permitted" that were actually -1 mistaken for -EPERM. Also too many
functions that return -1 for some failures and -errno for others.
I just want to add one note:
OK, you like the pattern
if (func()) {
<handle error>
}
, I can live with it.
I believe, we have a lot of such patterns already in code.
Now, we are going to add a lot of functions, returning true on success and
false on failure, so add a lot of patterns
if (!func()) {
<handle error>
}
---
After it, looking at something like
if (!func()) {} / if (func()) {}
I'll have to always jump to function definition, to check is it int or bool
function, to understand what exactly is meant and is there a mistake in the
code..
So, I'm afraid that such conversion will not help reviewing/understanding the
code. I'd prefer to avoid using two opposite conventions in on project.
I can also imagine combining different function types (int/bool) in if
conditions o_O, what will save us from it?
And don't forget about bool functions, which just check something, and false is
not an error, but just negative answer on some question.
--
Best regards,
Vladimir
