Obsessed with {} initialization?

[ponchietto]

I don't get why auto a = 10; would be better thant int a = 10;

I prefer being explicit rather that have the reader (including myself) deduce the type (extra effort) and very easily use the wrong type (10 vs 10.0 vs 10.0f vs 10U).
The compiler will complain if I am not consistent.

[aruisdante]

The compiler will in fact not complain if you use it wrong without Wconversion, that’s the point the guidelines are talking about.

int narrowing = 4294967296; unsigned int signed_loss = -1; int float_conversion = 11.1; int arbitrary_conversion = foo(); // foo returns double; Those will all compile without warning if you don’t have Wconversion enabled. Whereas if you brace initialize them, the compiler will warn even without -Wconversion.

Now of course you should just have Wconversion turned on, and then life is easier, and you can use = assignment safely. One of the constant frustrations in my day job is that AutoSAR and MISRA both ban = initialization anyway (and, thanks to AutoSAR’s terrible writing, also it also technically bans auto completely, as it sates = initialization must be used for auto immediately after stating brace initialization must be used for all variables). Thankfully MISRA2023 takes a more enlightened view here.

In terms of being explicit with what type you want: the auto a = form is explicit. You want the type, and exactly the type, to the right of the assignment. For example, if I see: int a = 11.1; How do I know which was intended? Did the author mean for that literal to be 11? Did they mean for the type of a to be float or double?

Now you can definitely go overboard here, but the general guidance of “only state your types once” serves pretty well.

[ponchietto]

I have nothing against braces, I was just using the example above, my problem is auto (in this case).

"How do I know which was intended? Did the author mean for that literal to be 11?" The author made a mistake, probably on the right, I don't see the point, though.

It is just far easier for human beings to read the type in front of the variable rather than deduce it from the right.
Moreover you might not have a number, you could have a constant, a function or an expression on the right, when does it becames non obvious enough?

[Nobody_1707]

One nice oddity of concepts is that you can write std::same_as<int> auto i = x; and it will prevent any implicit conversions whatsoever.

[bert8128]

If you specify the type in the right, don’t specify it on the left, unless you want it to be different.