zend_inheritance.c: make a bunch of pointers const

[DanielEScherzer]

No description provided.

[iluuu1994]

Thanks @DanielEScherzer! Before continuing this work, I think it would be good to have some consensus on how we want to continue on this matter. In reality, I don't think local const declarations are super useful, because they are mostly inferrable by the compiler. What is more useful is const declarations in exported function signatures because they (possibly?) enable some additional compiler optimizations, but they are also breaking, which is why they are avoided here.

I'm not sure where this conversation should be held. The ML is generally not a great place, because most people there aren't C developers and will still generate a lot of noise.

[iluuu1994]

Maybe @cmb69 @arnaud-lb @nielsdos can pitch by sharing their opinion.

[cmb69]

In reality, I don't think local const declarations are super useful, because they are mostly inferrable by the compiler.

In my opinion, this is not only about the compiler, but also for developers reading the code. One particular issue are pointers, though. Some reading const zval *zv may assume that zv can't be reassigned, but that is not the case in C (you would need zval * const zv for this).

Even for local variable declarations either form of constness (or even both) can make sense, but I don't think it would be a good idea to go through the whole code base and change that. It might be better if this is part of some larger refactorings for particular parts of php-src; there is still a huge amount of code suffering from accidential complexity, which could be improved.

[nielsdos]

I agree const is mostly for developers. In fact, I don't think the C compiler really uses the fact something is const since you can just cast it away (I think it's not allowed in C++ though).
I also don't think it's a good idea to change everything in one go.

[DanielEScherzer]

In reality, I don't think local const declarations are super useful, because they are mostly inferrable by the compiler.

In my opinion, this is not only about the compiler, but also for developers reading the code. One particular issue are pointers, though. Some reading const zval *zv may assume that zv can't be reassigned, but that is not the case in C (you would need zval * const zv for this).

Even for local variable declarations either form of constness (or even both) can make sense, but I don't think it would be a good idea to go through the whole code base and change that. It might be better if this is part of some larger refactorings for particular parts of php-src; there is still a huge amount of code suffering from accidential complexity, which could be improved.

Sure - I like to write code, so if you want to point me to the parts that need refactoring, I'm happy to make an attempt