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0 pointsmaccard1y ago0 comments

Every language has inconsistencies, and C is not stranger to that. Much of c++’s baggage is due to C and you carry the same weight. That’s not to say that initialization isn’t broken in C++, but just like many features in many languages (off the top of my head in C - strcpy, sprintf, ctime are like hand grenades with the pin pre pulled for you) don’t use them. There’s a subset of C++17 that to me solves so many issues with C and C++ that it just makes sense to use. An example from a codebase I spend a lot of time in is

    int val;
    bool valueSet = getFoo(&val);
    if (valueSet) {}
    printf(“%d”, val); // oops

The bug can be avoided entirely with C++

    if (int val; getFoo(&val)) // if you control getFoo this could be a reference which makes the null check in getFoo a compile time check
    {}
    printf(“%d”, val); // this doesn’t compile.

0 comments

ho_schi1y ago

For C users. And C++ users:

In C++ we can declare variable in the while or if statement:

https://en.cppreference.com/w/cpp/language/while

https://en.cppreference.com/w/cpp/language/if

It's value is the value of the decision. This is not possible with C [1].

Since C++17 the if condition can contain an initializer: Ctrl+F if statements with initializer

https://en.cppreference.com/w/cpp/language/if

Which sounds like the same? Now you can declare a variable and it value is not directly evaluated, you also can compare it in a condition. I think both are neat features of C++, without adding complexity.

[1] Also not possible with Java.

trelane1y ago

Declaring a variable in a loop or if statement is supported since C99: https://en.wikipedia.org/wiki/C99

Also in Java: https://www.geeksforgeeks.org/for-loop-java-important-points...

ho_schi1y ago

Regarding Java:

It is possible that you confuse while- and for statements?

maccardOP1y ago

No, declaring a variable in a `for` loop is supported in C99 but you can't do if-init.

2 more replies

ablob1y ago

You could write this in C, no?

  { int val; if (getFoo(&val)) {
    ...
  }}

Both ways of expressing this are weird, but stating that this can't be achieved with C is dishonest in my opinion.

maccardOP1y ago

If I reformat this,

    {
        int val; 
        if (getFoo(&val)) {
    
        }
        printf("%d", val);
    }

The bug is still possible, as you've introduced an extra scope that doesn't exist in the C++ version.

Also, this was one example. There are plenty of other examples.

i_am_a_peasant1y ago

it's not that weird to explicitly limit the scope of certain variables that logically belong together.

But i agree the C++ if(init;cond) thing was new to me.

maccardOP1y ago

Like everything in C++, it has it's share of footguns

    if (Foo* f = GetPtr(); f->HasValue()) {} // wrong; f can be null

    if (Foo* f = GetPtr(); f && f->HasValue()){}

Is probably the biggest pitfall. Especially if you're used to this:

    if (Foo* f = GetPtr())
    {
        f->DoTheThing(); // this is perfectly safe.
    }

tialaramex1y ago

Variables like "valueSet" scream out that the language lacks a Maybe type instead. One of the worst things about C++ is that it's content to basically not bother improving on the C type system.

maccardOP1y ago

C++ has optional, but I wanted to demonstrate that you could wrap a C API in a safer more ergonomic way.

If you rewrote it in a more modern way and changed the API

    std::optional<int> getFoo();

    if (auto val = getFoo()) {}

There are lots of improvements over C’s type system - std.array, span, view, hell even a _string_ class

pjmlp1y ago

I would vouch that C++ has plenty of improvements of C type system, even C++ARM already provided enough improvements that I never liked plain old C, other than that year spent learning C via Turbo C 2.0, before being given access to Turbo C++ 1.0 for MS-DOS in 1993.

The problem is all the folks that insist coding in C++ as if it was C, ignored all those C++ improvements over C.

rowanG0771y ago

C++ has a maybe type. It's called std::optional.

uecker1y ago

Here is my experimental maybe type for C: https://godbolt.org/z/YxnsY7Ted

1 more reply

uecker1y ago

This will be in C2Y and is already supported by GCC 15: https://godbolt.org/z/szb5bovxq

maccardOP1y ago

This is one example. Off the top of my head std.array vs "naked" C arrays, string vs const char*, and let's not forget RAII are all features that just make me never want to work with vanilla C ever again.

uecker1y ago

For me, std.array seem fundamentally inferior compared to C arrays. A good standard string type is indeed missing, but it is also easy to define one. RAII, I can see, but I also some advantages to have explicit resource deallocation visible in the code and it is not really bothering me too much to write this explicitly.

j / k navigate · click thread line to collapse

0 comments

ho_schi1y ago

For C users. And C++ users:

In C++ we can declare variable in the while or if statement:

https://en.cppreference.com/w/cpp/language/while

https://en.cppreference.com/w/cpp/language/if

It's value is the value of the decision. This is not possible with C [1].

Since C++17 the if condition can contain an initializer: Ctrl+F if statements with initializer

https://en.cppreference.com/w/cpp/language/if

[1] Also not possible with Java.

trelane1y ago

Declaring a variable in a loop or if statement is supported since C99: https://en.wikipedia.org/wiki/C99

Also in Java: https://www.geeksforgeeks.org/for-loop-java-important-points...

ho_schi1y ago

Regarding Java:

It is possible that you confuse while- and for statements?

maccardOP1y ago

No, declaring a variable in a `for` loop is supported in C99 but you can't do if-init.

2 more replies

ablob1y ago

You could write this in C, no?

  { int val; if (getFoo(&val)) {
    ...
  }}

Both ways of expressing this are weird, but stating that this can't be achieved with C is dishonest in my opinion.

maccardOP1y ago

If I reformat this,

    {
        int val; 
        if (getFoo(&val)) {
    
        }
        printf("%d", val);
    }

The bug is still possible, as you've introduced an extra scope that doesn't exist in the C++ version.

Also, this was one example. There are plenty of other examples.

i_am_a_peasant1y ago

it's not that weird to explicitly limit the scope of certain variables that logically belong together.

But i agree the C++ if(init;cond) thing was new to me.

maccardOP1y ago

Like everything in C++, it has it's share of footguns

    if (Foo* f = GetPtr(); f->HasValue()) {} // wrong; f can be null

    if (Foo* f = GetPtr(); f && f->HasValue()){}

Is probably the biggest pitfall. Especially if you're used to this:

    if (Foo* f = GetPtr())
    {
        f->DoTheThing(); // this is perfectly safe.
    }

tialaramex1y ago

Variables like "valueSet" scream out that the language lacks a Maybe type instead. One of the worst things about C++ is that it's content to basically not bother improving on the C type system.

maccardOP1y ago

C++ has optional, but I wanted to demonstrate that you could wrap a C API in a safer more ergonomic way.

If you rewrote it in a more modern way and changed the API

    std::optional<int> getFoo();

    if (auto val = getFoo()) {}

There are lots of improvements over C’s type system - std.array, span, view, hell even a _string_ class

pjmlp1y ago

The problem is all the folks that insist coding in C++ as if it was C, ignored all those C++ improvements over C.

rowanG0771y ago

C++ has a maybe type. It's called std::optional.

uecker1y ago

Here is my experimental maybe type for C: https://godbolt.org/z/YxnsY7Ted

1 more reply

uecker1y ago

This will be in C2Y and is already supported by GCC 15: https://godbolt.org/z/szb5bovxq

maccardOP1y ago

uecker1y ago

j / k navigate · click thread line to collapse