Modern C

and what we can learn from it

By Luca Sas

Modern C?

Modern C?

• What if there is more to C than meets the eye?

Goals

Goals

• Present a modern way in which C can be used.

Goals

• Present a modern way in which C can be used.�
• Explore how ideas inspired from C can improve our C++ code.

Goals

• Present a modern way in which C can be used.�
• Explore how ideas inspired from C can improve our C++ code.�
• Showcase how these ideas manifest in other languages, old and new.

About me

Core Systems Engineer @ Creative Assembly

Game Development

Low Level Systems

Programming Languages

BananyaDev#0001

@SasLuca

sas.luca.alex@gmail.com

@

A refresh on C

A refresh on C

• Developed in 1972 (49 years ago)

A refresh on C

• Developed in 1972 (49 years ago)�
• Standardized by ANSI and later by ISO (ANSI C, C89, C99, C11, …)

A refresh on C

• Developed in 1972 (49 years ago)�
• Standardized by ANSI and later by ISO (ANSI C, C89, C99, C11, …)�
• C does still have an active ISO committee (WG14)

A refresh on C

A refresh on C

• Developed in 1972 (49 years ago)�
• Standardized by ANSI and later by ISO (ANSI C, C89, C99, C11, …)�
• C does still have an active ISO committee (WG14)�
• What have we missed in the past 50 years and how is C different from C++?

Variables and structs

Variables and structs

Primitive types

Primitive types

Primitive types

Functions

C++ is not C

• C++ is not fully compatible with C.

C++ is not C

• C++ is not fully compatible with C.�
• They are compatible enough that C headers will mostly work in C++.

C++ is not C

• C++ is not fully compatible with C.�
• They are compatible enough that C headers will mostly work in C++.�
• C++ did inherit a lot of baggage from this attempted compatibility with C.

What else is different between C and C++?

Struct initialization

Struct initialization

• Unlike C++, structs in C are just plain old bags of data (PODs)

Struct initialization

• Unlike C++, structs in C are just plain old bags of data (PODs)�
• C99 introduces a new and powerful form of struct initialization.

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

Struct initialization

• Unlike C++, structs in C are just plain old bags of data (PODs)�
• C99 introduces a new and powerful form of struct initialization.�
• We can easily initialize complex data structures with nested initializers.

Struct initialization

• Unlike C++, structs in C are just plain old bags of data (PODs)�
• C99 introduces a new and powerful form of struct initialization.�
• We can easily initialize complex data structures with nested initializers.�
• Everything we don’t explicitly initialize gets set to 0 (ZII).

Struct initialization

• Unlike C++, structs in C are just plain old bags of data (PODs)�
• C99 introduces a new and powerful form of struct initialization.�
• We can easily initialize complex data structures with nested initializers.�
• Everything we don’t explicitly initialize gets set to 0 (ZII).�
• This enabled more declarative and modern styles of programing.

Struct initialization

• Unlike C++, structs in C are just plain old bags of data (PODs)�
• C99 introduces a new and powerful form of struct initialization.�
• We can easily initialize complex data structures with nested initializers.�
• Everything we don’t explicitly initialize gets set to 0 (ZII).�
• This enabled more declarative and modern styles of programing.�
• C++ finally caught up after 20 years.

Struct initialization: sokol gfx

Struct initialization: sokol gfx

What Modern C is

• Challenging the way APIs have historically been structured in C.

What Modern C is

• Challenging the way APIs have historically been structured in C.�
• Using newer features of C in order to improve the ease of use and safety of the API.

What Modern C is

• Challenging the way APIs have historically been structured in C.�
• Using newer features of C in order to improve the ease of use and safety of the API.
• Decoupling the data manipulations from hosted services (allocators, io).

What Modern C is

• Challenging the way APIs have historically been structured in C.�
• Using newer features of C in order to improve the ease of use and safety of the API.
• Designing systems with portability and ease-of-use in mind. (Allocators, centralizing resources, separating hosted code from freehosted code)

C11 Additions

• The latest major version.

C11 Additions

• The latest major version.�
• As of recent it is now supported by all major compilers including MSVC.

C11 Additions: static assert

C11 Additions: _Generic and overloading

C11 Additions: Atomic operations

C11 Additions: thread_local

C11 Additions: thread_local

C11 Additions

• The latest major version.�
• As of recent it is now supported by all major compilers including MSVC.�
• Static_assert.�
• Overloading.�
• atomics (available in older versions with libraries like c89atomics).�
• thread_local (available via compiler extensions in C99).

Awesome Macros

Awesome Macros

• Macros CAN be evil!

Awesome Macros

• Macros CAN be evil!�
• There are some cases in which they can make our life much nicer.

Awesome Macros: defer

Awesome Macros: defer

Awesome Macros: defer

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Awesome Macros: defer

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Awesome Macros: defer

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Awesome Macros: defer

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API Design

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API Design: Math

API Design: Math

- Out params are harder to spot at the call site

API Design: Math

- Out params are harder to spot at the call site

- There are indirection and aliasing issues caused by the pointers which can harm performance

API Design: Math in Modern C

- value oriented design

API Design: Math in Modern C

- value oriented design

- we can use literals in the function call and readability is improved

API Design: Math in Modern C

- value oriented design

- we can use literals in the function call and readability is improved

- performance is actually better

API Design: Math in Modern C

API Design: Error handling

API Design: Error handling

API Design: Error handling

API Design: Error handling

API Design: Error handling in Modern C

Error handling in Modern C

Error handling in Modern C

Error handling in Modern C

Error handling in C++ with optional

Error handling in Modern C

Error handling in Modern C

Error handling in Modern C

Error handling: std::expected

Error handling in Rust

Error handling in Zig

Error handling in C++

Generic APIs in C

• C lacks generic programming (eg: templates)

Generic APIs in C

• C lacks generic programming (eg: templates).�
• C can also force us to think outside the box and not rely excessively on templates.

Generic APIs in C

• C lacks generic programming (eg: templates).�
• C can also force us to think outside the box and not rely excessively on templates.�
• There do exist some solutions for some very common use cases.

Generic APIs in C: Trees and Graphs

Generic APIs in C: Trees and Graphs

Generic APIs in C: Dynamic Arrays

Generic APIs in C: Dynamic Arrays

Generic APIs in C: Dynamic Arrays

Generic APIs in C: Dynamic Arrays

Generic APIs in C: Map

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https://github.com/nothings/stb/blob/master/stb_ds.h

Libraries in C

• Historically messy due to the multitude of build systems and no standard.

Libraries in C

• Historically messy due to the multitude of build systems and no standard.�
• Single header libraries arise as a convenient way to solve this problem.

Libraries in C

• Historically messy due to the multitude of build systems and no standard.�
• Single header libraries arise as a convenient way to solve this problem.

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Libraries in C

• Historically messy due to the multitude of build systems and no standard.
• Single header libraries arise as a convenient way to solve this problem.

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• Sane CMake is another good option. Single headers can optionally be auto-generated.

Great talk on Cmake

Libraries in newer languages

• Newer langs improve significantly on the library situation.�
• Rust has a very well received easy to use build system and centralized database for libraries.�
• Zig takes a unique approach by having the build system be part of the language.

When writing libraries

• Avoid allocations if possible, request allocators or buffers from the user.

When writing libraries

• Avoid allocations if possible, request allocators or buffers from the user.�
• Try and make your library freehosted.

When writing libraries

• Avoid allocations if possible, request allocators or buffers from the user.�
• Try and make your library freehosted.

Memory management

• Consider centralizing allocations.�
• Differentiate between temporary and long lived allocations.�
• Use buffers with maximum sizes where possible.�
• Consider handles instead of pointers (eg: ECS)

Temporary allocators

Temporary allocators

Temporary allocators

API Design: Modern C

• More declarative and functional, less stateful.�
• More value oriented and less pointers.�
• Zero initialization is used heavily (ZII)�
• Uses C99 and C11 features and macros to modernize the code.�
• Centralized resource management.�
• Allocator aware.

String handling in C

• Strings in C have been a historical disaster.

String handling in C

• Strings in C have been a historical disaster.�
• Terrible standard API (strstr, strtok, strpbrk).

Public service announcement: avoid libc

• Very old�
• Slow�
• Terrible API design�
• Very few parts are actually useful (stdint.h, memmove/memcpy/memset, math.h)

Replacing libc functionality: printf

String handling in C

• Strings in C have been a historical disaster.�
• Terrible standard API (strstr, strtok, strpbrk).�
• Null terminated strings are very slow.

It’s not just null terminated strings

Case study: std::string

Intent: reading an array of bytes representing text

Case study: std::string

What’s the problem with a few couple of temporary strings here and there?

Real life examples:�Chrome

• Half of all allocations are std::string.

Real life examples:�Chrome

• Half of all allocations are std::string.

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• Typing one character in the Omnibox used to result in over 25000 allocations.

Real life examples:�Chrome

• Half of all allocations are std::string.

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• Typing one character in the Omnibox used to result in over 25000 allocations.

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• Performance issues resulted from lot’s of copies and temporary objects.

String handling in Modern C

• No implicit conversions and constructors.

String handling in Modern C

• No implicit conversions and constructors.�
• Stronger distinction between owning and non-owning strings.

String handling in Modern C

String handling in Modern C

String handling in Modern C

String handling in Modern C

String handling in Modern C

String handling in Old C

String handling in Old C

String handling in Modern C

String handling in Modern C: overloading

String handling in Modern C: overloading

String handling in Modern C: another awesome macro

String handling in Modern C: another awesome macro

First optimization at CA

• First ever optimization I did at Creative Assembly was related to string operations.

First optimization at CA

• First ever optimization I did at Creative Assembly was related to string operations.�
• A seemingly cheap function was splitting some string.

First optimization at CA

• First ever optimization I did at Creative Assembly was related to string operations.�
• A seemingly cheap function was splitting some string.�
• The function didn’t seem to take much time unless you analyzed its cost cumulatively.

First optimization at CA

• First ever optimization I did at Creative Assembly was related to string operations.�
• A seemingly cheap function was splitting some string.�
• The function didn’t seem to take much time unless you analyzed its cost cumulatively.�
• The solution was to move to a non-allocating, lazily evaluated string splitter using std::string_view.

String handling in other languages

• Rust has a built-in str type which is different from the owning String class.�
• Zig and Odin have built-in array-view types and string-view manipulation functions.�
• Java and C# also follow a similar model.

String handling in C++

• Consider starting to use std::string_view instead of const std::string& in C++.�
• C++17 added std::string_view.�
• C++20 ranges will make lazy non-allocating algorithms more easy to use.

In conclusion

• I hope that you gained a better appreciation for what can be done in a limited language like C.

In conclusion

• I hope that you gained a better appreciation for what can be done in a limited language like C.�
• Checkout the latest developments in C, C++ and also other systems languages.

In conclusion

• I hope that you gained a better appreciation for what can be done in a limited language like C.�
• Checkout the latest developments in C, C++ and also other systems languages.�
• Re-examine some of the patterns and preconceptions that you may hold.

In conclusion

• I hope that you gained a better appreciation for what can be done in a limited language like C.�
• Checkout the latest developments in C, C++ and also other systems languages.�
• Re-examine some of the patterns and preconceptions that you may hold.�
• By challenging our current understanding and not taking things for granted we can discover new and better ways of doing things.

Shoutouts

Modern C for C++ Peeps: https://floooh.github.io/2019/09/27/modern-c-for-cpp-peeps.html

�Odin: https://odin-lang.org/

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Zig: https://ziglang.org/

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Handmade Hero: https://handmadehero.org/��Handmade Network: https://handmade.network/

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