C Legacy Is Evil

http://kalnitsky.org/2014/10/25/c-legacy-is-evil/

by ikalnitsky • 12 years ago

18 31 12 years ago

kalnitsky.org

JoeAltmaier3• 12 years ago

I clear structs using a template; saves copying and screwing up the length:

template <class C> SPL_INLINE_FORCE void Zero(C &c) { memset(&c, 0, sizeof(c)); }

struct tm tm_struct;

Zero(tm_struct);

dezgeg2• 12 years ago

There's also a way to do this without any user-defined functions that works in both C and C++:

    struct tm tm_struct = { 0, };

cremno• 12 years ago

In ISO C++ and GNU C you can also omit the 0:

    struct tm tm_struct = { };

JoeAltmaier3• 12 years ago

Does that work on char array members in the struct?

throwaway7808• 12 years ago

At least in C your initialization functions are first class citizens. Not like in that messed-up language, in which a constructor just should not fail...

thegeomaster2• 12 years ago

What do you mean by "a constructor just should not fail?" Constructors can and do fail in C++.

stephencanon2• 12 years ago

Of course, in C you'd just use designated initializers and avoid the problem entirely (any unspecified fields are zero-initialized).

mamcx7• 12 years ago

Bad correlation.

This is about a bad language that force GOOD developers to figth against it.

"Always use memset onto struct variable before usage, because by default it's filled with garbage."

See? The language PUT GARBAGE on your code. Good or bad developer, not matter.

Now, a more experienced developer will remember that it need to correct the problems the language force on ALL the users.

Not all the blame is in the people. Somethings, the tools are at fault, too..

oceanstone• 12 years ago

The language just gave you a block of memory. It lets you decide whether you'd like to dedicate resources to clearing that memory.

fla• 12 years ago

No, the compiler avoids unecessary work unless you ask it to.

thegeomaster2• 12 years ago

See? The language PUT GARBAGE on your code.

It didn't put it there. It just allocated some memory. Not more, not less. If you, for example, malloc a large chunk of memory but don't intend to use it sequentially or not right away, you can save time by not memset'ing it to zero, which would be pointless. C gives you the liberty to defer the initialization, but if you're careless, you'll shoot yourself in the foot. It's very much like having a car with manual vs. automatic transmission. More power = more responsibility. If you need power, you have to accept some compromises, and in this case, the compromise is that you need to mind what's in your memory all the time.

kazinator• 12 years ago

And designated initializers will eventually creep into C++.

notacoward2• 12 years ago

Yes, it's possible to make mistakes in C. News at 11. Some mistakes are unique to C, some are shared with C++, and a bloody huge heap of them are unique to C++. What is proven by picking one bug from the first or second bucket and ignoring the third?

millstone• 12 years ago

If you wrote your own struct in C++, you have to define constructor to initialize all members with some default values.

No you don't. You are free to define a constructor that leaves some fields as garbage; in fact that's the default behavior.

patmcguire• 12 years ago

As long as we're purging evil legacy, this particular bug could also be solved by getting rid of daylight savings time and updating the struct accordingly.

Sonicmouse• 12 years ago

I don't get it?

He didn't initialize a struct properly, results in errors...

Conclusion: C is evil?

yongjik• 12 years ago

I'm sure Bjarne Stroustrup (and the C++ committee) had enough time and resource to mandate that structures are zero-initialized, if they were so inclined. (I mean, think about it: any time you read from an uninitialized value is an undefined behavior, so no conforming program will be broken by this change. Literally.)

The fact that they didn't tells me that this was a conscious decision, not some "Legacy C" cruft that's left there for the sake of backward compatibility. And indeed the core tenet of C++ is "You only pay for what you use", isn't it? Zero-initializing a struct would be against C++'s philosophy.

C Legacy Is Evil

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