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0 pointsfoxhill11y ago0 comments

DRY principle - you give the variables a name once, in the function definition. e.g:

    //decl in the header
    int pow(int exponent, int base);

if you only look at the header you might think that the arguments are one way, but

    //actual definition
    int pow(int base, int exponent){
      //math is correct but base <-> exponent..
    }

i'm not saying i agree with this at all - it's a contrived example..!

0 comments

tedunangst11y ago

CVE-2014-3956

erhardm11y ago

Replying with a CVE is like icing on the cake. :) It really shows that OpenBSD devs take security seriously. Funny timing, I was just reading Absolute OpenBSD.

steveklabnik11y ago

It also demonstrates that sometimes, there are additional constraints that you may not understand in choices you may not agree with.

bigfoot11y ago

OK, agreed. C (and C++) just suck regarding this detail.

ajross11y ago

I don't see how that's relevant.

The bug in that CVE is that the function call got the parameter order wrong. The declaration was correct AFAICT, and of course completely irrelevant because you can make that mistake regardless of what the header says.

Parameters in headers are just documentation, by definition. Documentation can be wrong however you write it, but in general it helps to have it instead of not. Would you seriously argue that function parameters should not be given names in documentation?

clarry11y ago

> The bug in that CVE is that the function call got the parameter order wrong. The declaration was correct AFAICT

Actually if you look at the patch to fix this issue, they swap the identifiers in the declarator. Of course when something like this happens, you're free to choose whether the definition or the callers should be changed.

https://www.FreeBSD.org/security/patches/SA-14:11/sendmail.p...

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foxhillOP11y ago

i would argue that had the function prototype had names for it's arguments that this might not have happened.

cesarb11y ago

Hm. This is the kind of thing where a compiler warning could be useful. I took a quick look at gcc's manual, but it does not seem to have a warning for this particular mistake (argument names do not match between declaration and definition).

That way, you could repeat yourself safely, since the repetition would be checked by the compiler.

hga11y ago

I did a quick -Wall test with gcc 4.4.5 and it doesn't warn.

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