Is C++ competely separated from it's standard library?

[Trinopoty]

C (not C++) as a language is pure and is completely separated from the standard library that comes with it. You can write a C program and it will compile and run fine without any standard library in place.

Can the same be said for C++? I know the the STL is almost integrated into the C++ language itself by means of the new and delete keywords at least.

Is it possible to disable the STL completely and still be able to compile C++ code?

[Sauron]

9 minutes ago, Trinopoty said:

Can the same be said for C++?

Yes, so long as you don't use anything in the STL...

[Trinopoty]

1 minute ago, Sauron said:

Yes, so long as you don't use anything in the STL...

So as long as you don't use the STL, you can remove it and the compiler won't complain?

Is there a bare minimum amount of runtime support that would be required for C++ even without the STL? Apart from the stack.

[Sauron]

10 minutes ago, Trinopoty said:

So as long as you don't use the STL, you can remove it and the compiler won't complain?

Is there a bare minimum amount of runtime support that would be required for C++ even without the STL? Apart from the stack.

No, that's only a thing with shared libraries afaik.

[straight_stewie]

9 hours ago, Trinopoty said:

So as long as you don't use the STL, you can remove it and the compiler won't complain?

You have to declare that you're using "stuff" from the STL for the "compiler" to even "bring it in".

 

That's what #include statements are.

 

For example:

int main()
{
  std::cout << "Hello World!" << std::endl;
}

Will give you an error about not knowing what "std::cout" is, but:

#include <iostream>

int main()
{
  std::cout << "Hello World" << std::endl;
}

will compile.

[Unimportant]

10 hours ago, Trinopoty said:

C (not C++) as a language is pure and is completely separated from the standard library that comes with it. You can write a C program and it will compile and run fine without any standard library in place.

Can the same be said for C++? I know the the STL is almost integrated into the C++ language itself by means of the new and delete keywords at least.

Is it possible to disable the STL completely and still be able to compile C++ code?

The STL is header only, perhaps you mean the runtime libraries?

[Trinopoty]

3 hours ago, Unimportant said:

The STL is header only, perhaps you mean the runtime libraries?

Whatever it is that provides stuff like new, delete, etc.

[wanderingfool2]

9 minutes ago, Trinopoty said:

Whatever it is that provides stuff like new, delete, etc.

new, delete, ->, and things such as that are part of the C++ definition.

 

Just like how in c vs ansi c, // is valid for c, but // isn't valid for ansi c (different standards).

[Trinopoty]

8 hours ago, wanderingfool2 said:

new, delete, ->, and things such as that are part of the C++ definition.

 

Just like how in c vs ansi c, // is valid for c, but // isn't valid for ansi c (different standards).

But doesn't new and delete require runtime support since they operate on a heap which is an external thing.

[Unimportant]

4 hours ago, Trinopoty said:

But doesn't new and delete require runtime support since they operate on a heap which is an external thing.

Yes, they are provided by the runtime library (often delegated to malloc under the hood).  Most platforms combine the runtime and standard library into one. If you compile without it you lose the bootstrapping and proper exit code along with the standard library functions.

 

The STL is a template library and because the compiler needs to be able to see the full implementation of templates at the point they're invoked, the headers ARE the full implementation, there should be no separate binaries for the STL.

 

 

[Trinopoty]

2 hours ago, Unimportant said:

Yes, they are provided by the runtime library (often delegated to malloc under the hood).  Most platforms combine the runtime and standard library into one. If you compile without it you lose the bootstrapping and proper exit code along with the standard library functions.

 

The STL is a template library and because the compiler needs to be able to see the full implementation of templates at the point they're invoked, the headers ARE the full implementation, there should be no separate binaries for the STL.

 

 

So it's not possible to completely disable the runtime library?

[Unimportant]

3 hours ago, Trinopoty said:

So it's not possible to completely disable the runtime library?

You can but you'll have to do all the setup yourself and it's platform dependant.

Here's the documentation for MSVC https://docs.microsoft.com/en-us/cpp/build/reference/nodefaultlib-ignore-libraries?view=vs-2019

[wanderingfool2]

4 hours ago, Trinopoty said:

So it's not possible to completely disable the runtime library?

So, is there a specific reason for asking these questions.  I am genuinely curious, as even embedded systems can run standard c++ stuff.

[straight_stewie]

20 hours ago, Trinopoty said:

Whatever it is that provides stuff like new, delete, etc.

11 hours ago, Trinopoty said:

But doesn't new and delete require runtime support since they operate on a heap which is an external thing.

Do you really just want to program in C?

If you disable the runtime library you're going to lose support for most features that differentiate C++ from C anyway.

 

C also requires a runtime library for some features to work correctly, so I guess I really should be asking: Do you really just want to program in assembly?

[SwiftGTi]

You can setup your compiler to adhere to certain C++ standards, which won't require any runtime libraries. But as some have pointed out, you will get much closer to pure C, but use classes and certain functions that are C++ specific.

[Trinopoty]

2 hours ago, wanderingfool2 said:

So, is there a specific reason for asking these questions.  I am genuinely curious, as even embedded systems can run standard c++ stuff.

Just curious as to how C++ in the embedded world works with where a runtime does not exist.

[wanderingfool2]

24 minutes ago, Trinopoty said:

Just curious as to how C++ in the embedded world works with where a runtime does not exist.

I haven't really done anything in the world of embedded systems, so I could be wrong and maybe someone can correct me...but from my knowledge, STL exists on most embedded system compilers

[igormp]

On 5/6/2020 at 3:21 AM, Trinopoty said:

C (not C++) as a language is pure and is completely separated from the standard library that comes with it. You can write a C program and it will compile and run fine without any standard library in place.

Can the same be said for C++? I know the the STL is almost integrated into the C++ language itself by means of the new and delete keywords at least.

Is it possible to disable the STL completely and still be able to compile C++ code?

Yes, simply pass -nostdlib -fno-exceptions -fno-rtti to your compiler and enjoy.

 

As a side note, I believe you're mistaking what the C stdlib is, since you'd go through the same pain with both C and C++ if you're passing the above mentioned flags (you can read more about it here for C and here for C++).

 

Most embedded devices have a C stdlib (take newlib, as an example), which is fundamental for basic tasks such as calling malloc and whatnot, and since the C++ std library only makes calls to to the functions on the C stdlib, it's not hard to have support for it.

 

On 5/7/2020 at 1:33 PM, straight_stewie said:

Do you really just want to program in C?

If you disable the runtime library you're going to lose support for most features that differentiate C++ from C anyway.

You still get classes and templates 

When you're really tight on program memory, including a fat and somewhat generic stdlib may not be useful, so you might want to roll your own.

[JacobFW]

Someone please correct me if I'm wrong or missing something.

 

For many operations, no you don't need any standard libraries, but once you start dealing with entities outside of your program (i.e. files, display output, get keyboard/mouse data), that's there things start getting tricky.

As I recall there is a difference between programming for Unix/Unix like systems and programming for Windows.  With Unix, you can use interrupts to communicate with the OS, open files, display text, get keyboard data, etc.  But Windows doesn't allow you to do that.  Instead you're program links to the CRT Library, which has the actual code in DLL's. 

 

[straight_stewie]

25 minutes ago, JacobFW said:

As I recall there is a difference between programming for Unix/Unix like systems and programming for Windows.  With Unix, you can use interrupts to communicate with the OS, open files, display text, get keyboard data, etc.  But Windows doesn't allow you to do that.  Instead you're program links to the CRT Library, which has the actual code in DLL's. 

My understanding is nowhere near expert level, but that's not quite correct.

 

The CRT is just the C RunTime Library.

You can use interrupts and even register your own ISRs if you're writing something like a driver.

Otherwise for Win32 apps you get a collection of classes, functions, and services, and windows sends you messages through the WinProc callback function.

I've experimented with it a bit, but for nothing major or useful.

[igormp]

1 hour ago, JacobFW said:

For many operations, no you don't need any standard libraries, but once you start dealing with entities outside of your program

You still need something to set up memory and whatnot for you, the stdlib takes care of that.