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c-standard-library [February 20, 2026 at 02:23] – yanevskivc-standard-library [May 14, 2026 at 11:38] (current) – external edit 127.0.0.1
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 +# C standard library
 +**C standard library** is one library that's always linked by default when you compile C programs.
 +
 +To use the library, a set of headers is offered which you can include by default.
 +
 +For example, `<stdlib.h>` and `<stdio.h>` in this code are headers from the C standard library (but there are also headers which are *not* part of C standard library!).
 +
 + - `<stdlib.h>` provides a definition of the constant `EXIT_SUCCESS`
 + - `<stdio.h>` provides a declaration to the function `printf()`
 +
 +```c
 +// Compile: gcc main.c -o program
 +// Run:     ./program
 +#include <stdlib.h>
 +#include <stdio.h>
 +
 +int main()
 +{
 +    printf("Hello world!");
 +
 +    return EXIT_SUCCESS;
 +}
 +```
 +
 +
 +## Headers
 +
 + - [[assert.h]]
 + - [[complex.h]]
 + - [[ctype.h]]
 + - [[errno.h]]
 + - [[fenv.h]]
 + - [[float.h]]
 + - [[inttypes.h]]
 + - [[iso646.h]]
 + - [[limits.h]]
 + - [[locale.h]]
 + - [[math.h]]
 + - [[setjmp.h]]
 + - [[signal.h]]
 + - [[stdalign.h]]
 + - [[stdarg.h]]
 + - [[stdatomic.h]]
 + - [[stdbit.h]]
 + - [[stdbool.h]]
 + - [[stdckdint.h]]
 + - [[stddef.h]]
 + - [[stdint.h]]
 + - [[stdio.h]]
 + - [[stdlib.h]]
 + - [[stdmchar.h]]
 + - [[stdnoreturn.h]]
 + - [[string.h]]
 + - [[tgmath.h]]
 + - [[thread.h]]
 + - [[time.h]]
 + - [[uchar.h]]
 + - [[wchar.h]]
 + - [[wctype.h]]
 +
 +
 +## What are headers for?
 +Headers commonly define various constants (`#define`) e.g. `<stdlib.h>` defines `EXIT_SUCCESS`
 +```bash
 + $ grep -e EXIT_SUCCESS < /usr/include/stdlib.h
 +#define EXIT_SUCCESS    0       /* Successful exit status.  */
 +```
 +
 +They also commonly declare various function calls e.g. `<stdio.h>` declares `printf()`
 +```bash
 + $ grep -e 'extern int printf' < /usr/include/
 +extern int printf (const char *__restrict __format, ...);
 +```
 +
 +And they also declare various `struct`s, `union`s, and `typedef`s
 +
 +
 +## Paths
 +All headers all live in `/usr/include` directory and have the file extension ".h" -- which stands for "header". For example
 +
 + - `/usr/include/stdio.h`
 +
 +The library itself lives in `/usr/lib`. It actually comes in two flavors:
 +
 + - `/usr/lib/libc.a` - Static library (.a stands for "archive")
 + - `/usr/lib/libc.so` - Dynamic library (.so stands for "shared object")
 +
 +## Static vs dynamic
 +
 +
 +## Austerity
 +Compared to standard libraries of modern programming languages -- such as Rust, C++17, Python, JavaScript etc. -- you'll find the C standard library frustratingly barren and austere.
 +
 +It contains almost nothing! 
 +
 +Furthermore, many parts of the standard library are either dangerous (`gets()`), confusing (`strtok()`), near-duplicates (`getc()` and `fgetc()`), or not actually part of thes standard at all (`itoa()`).
 +
 +## What's missing?
 +### No data structures
 +No maps. No vectors. No lists or trees. Nothing.
 +
 +If you want something like C++'s `std::vector` in C -- i.e. a dynamically grown array -- you'll have to go ahead make a `struct` for it and implement it yourself, with `calloc()`, `realloc()` and `free()`!
 +```
 +typedef struct _vector_t {
 +    void* v_data;
 +    size_t v_capacity;
 +    size_t v_size;
 +} vector_t;
 +```
 +But many data structures common in higher programming languages -- like C++'s `std::map` or Python's dict `{a: 1, b: 2}` -- are internally implemented through non-trivial data structures like B-trees or Red-black trees.
 +
 +While C might be conceptually the fastest programming language in existence (you're a hair away from writing machine code!) if you don't bother to implement fast data structures you won't see that.
 +
 +### No: string manipulation
 +
 +### No: serialization
 +No JSON. No YAML. No XML. No ini files. Nothing.
 +
 +### No: filesystem
 +No directory traversal. No file permission.
 +
 +### No: web
 +No sockets. No web servers. No requests. Nothing.
 +
 +### No: unicode
 +No emojis. No CJK, arabic.
 +
 +### No: async or multithreading
 +
 +## Hosted vs freestanding
 +
 +
 +## Links
 +
 + - https://en.cppreference.com/w/c/header.html
 + - https://sourceware.org/glibc/manual/latest/html_mono/libc.html
 + - https://sourceware.org/glibc/manual/latest/html_mono/libc.html