Does C guarantee short circuit evaluation?

[Syndacate]

As the title says..I know C++/Java do IIRC, but does C?

ie. safe practice?

if (!my_struct || !my_struct->my_ptr);

[CommonTater]

Safe... but not guaranteed to shortcircuit, far as I know...

[AndrewHunter]

Yes, it is guaranteed by the standard.

[Syndacate]

Safe... but not guaranteed to shortcircuit, far as I know...

How would it be not guaranteed but still safe? If 'my_struct' is a pointer, and short circuiting isn't guaranteed, then there's a chance of dereferencing a NULL pointer.

Yes, it is guaranteed by the standard. However note the logical OR means both sides need to be evaluated so no short circuiting is involved.

You're saying that it's only guaranteed for logical AND? Hrm, interesting. Seeing as a logical OR doesn't require both sides to be evaluated in terms of boolean logic, I'm surprised it needs to be by the compiler.

[AndrewHunter]

You're saying that it's only guaranteed for logical AND? Hrm, interesting. Seeing as a logical OR doesn't require both sides to be evaluated in terms of boolean logic, I'm surprised it needs to be by the compiler.

I edited out my nonsense. It is guaranteed by the standard to be short circuited and left to right evaluated for both the logical OR and AND. Sorry for my random stupidity( it happens sometimes, just ask Tater).

[Syndacate]

I edited out my nonsense. It is guaranteed by the standard to be short circuited and left to right evaluated for both the logical OR and AND. Sorry for my random stupidity( it happens sometimes, just ask Tater).

Haha, happens .

Just wanted to make sure it was reliable.

Thanks, guys, especially for the instantaneous replies, lol.

[AndrewHunter]

If you want to look it up yourself check out 6.5.14.4 for OR and 6.5.13.5 for AND in C99. It will be around there, I only have one of the draft versions.

[Syndacate]

If you want to look it up yourself check out 6.5.14.4 for OR and 6.5.13.5 for AND in C99. It will be around there, I only have one of the draft versions.

Ha, I'll take your word for it .

I have to get around to reading the whole draft spec when I get some free time - I'll save it until then ^_^.

Besides, only half the battle is it being in the draft spec, the other part is the (possibly bad) assumption that what you're using is 100% compliant with the C-spec, lol.

Also, this is C89 IIRC.

[AndrewHunter]

Ha, I'll take your word for it .
I have to get around to reading the whole draft spec when I get some free time - I'll save it until then ^_^.

I wouldn't rush, it isn't that interesting of a read.

Also, this is C89 IIRC.

The same rule applied in C89, I just quoted from C99 since it is the one I have handy at the moment.

[grumpy]

Guaranteed short-circuiting of logical expressions has always been a feature of C. It was true when Dennis Ritchie designed and implemented the first version of C, still true in the 1989 C standard, and remains true in the C99 standard.

[Syndacate]

I wouldn't rush, it isn't that interesting of a read.

Ha, not expecting it to be interesting, but you're pretty much guaranteed to learn tid-bits you didn't know about the language.

Guaranteed short-circuiting of logical expressions has always been a feature of C. It was true when Dennis Ritchie designed and implemented the first version of C, still true in the 1989 C standard, and remains true in the C99 standard.

Ah, good . Thanks!