sb

A C89 standard compliant, single header, nostdlib (no C Standard Library) String Builder (SB).

For more information please look at the "sb.h" file or take a look at the "examples" or "tests" folder.

Warning

THIS PROJECT IS A WORK IN PROGRESS! ANYTHING CAN CHANGE AT ANY MOMENT WITHOUT ANY NOTICE! USE THIS PROJECT AT YOUR OWN RISK!

Features

• C89 compliant — portable and legacy-friendly
• Single-header API — just include sb.h
• nostdlib — no dependency on the C Standard Library
• Minimal binary size — optimized for small executables
• Cross-platform — Works on all Platforms
• Strict compilation — built with aggressive warnings & safety checks (detect buffer overflow via sb.ovr)

Quick Start

Download or clone sb.h and include it in your project.

#include "sb.h" /* String Builder */

int main(void) {

    /* Initialize the string builder */
    char buf[256];
    sb sb;
    sb_init(&sb, buf, sizeof(buf));

    /* Examples for formatting numbers */
    sb_append_cstr(&sb, "  none: '");
    sb_append_long(&sb, 123, 8, SB_PAD_NONE);
    sb_append_cstr(&sb, "'\n");

    sb_append_cstr(&sb, "  left: '");
    sb_append_long(&sb, 123, 8, SB_PAD_RIGHT);
    sb_append_cstr(&sb, "'\n");

    sb_append_cstr(&sb, " right: '");
    sb_append_long(&sb, 123, 8, SB_PAD_LEFT);
    sb_append_cstr(&sb, "'\n");

    sb_append_cstr(&sb, "double: '");
    sb_append_double(&sb, -3.14159, 9, 4, SB_PAD_LEFT);
    sb_append_cstr(&sb, "'\n");

    sb_append_cstr(&sb, " float: '");
    sb_append_float(&sb, 0.1234f, 9, 4, SB_PAD_LEFT);
    sb_append_cstr(&sb, "'\n");

    /* Add terminator to string builder */
    sb_term(&sb);

    /* Afterwards you can print the "sb.buf" or "buf" directly */

    return 0;
}

Output will be:

  none: '123'
  left: '123     '
 right: '     123'
double: '  -3.1416'
 float: '   0.1234'

Function Reference

Function	Signature	Description	Return
Initialize SB	void sb_init(sb *sb, char *buffer, int capacity)	Initialize string builder with a buffer.	–
Terminate SB	void sb_term(sb *sb)	Null-terminate buffer, set overflow if needed.	–
Append character	void sb_putc(sb *sb, char c)	Append single character.	–
Append bytes	void sb_append_bytes(sb *sb, char *src, int len)	Append len bytes from a buffer.	–
Append C string	int sb_append_cstr(sb *sb, char *s)	Append null-terminated string.	Number of bytes appended
Append spaces	void sb_append_spaces(sb *sb, int count)	Append count space characters.	–
Append unsigned long	int sb_append_ulong(sb *sb, unsigned long v, int width, sb_pad_mode pad)	Append unsigned integer with optional width and padding.	Number of characters written
Append signed long	int sb_append_long(sb *sb, long v, int width, sb_pad_mode pad)	Append signed integer with optional width and padding.	Number of characters written
Append float	int sb_append_float(sb *sb, float x, int width, int precision, sb_pad_mode pad)	Append floating-point number with precision and optional padding.	Number of characters written
Append double	int sb_append_double(sb *sb, double x, int width, int precision, sb_pad_mode pad)	Append double with precision and optional padding.	Number of characters written
Compare SB to string	int sb_cmp(const sb *sb, const char *s)	Compare SB content to a C string. Returns 0 if equal, <0 if sb < s, >0 if sb > s.	Comparison result
Compare SB to string (up to n)	int sb_ncmp(const sb *sb, const char *s, int n)	Compare SB content to first n chars of a C string.	Comparison result

Notes on sb_printf

• Supported format specifiers:
  %s (string), %d (signed int), %u (unsigned int), %f (float/double), %c (char)
• Width & padding:
  • %5d → right-padded
  • %-5d → left-padded
• Precision:
  • %.2f → 2 digits after decimal
• Up to 8 arguments supported (sb_printf1 → sb_printf8).

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Run Example: nostdlib, freestsanding

In this repo you will find the "examples/sb_win32_nostdlib.c" with the corresponding "build.bat" file which creates an executable only linked to "kernel32" and is not using the C standard library and executes the program afterwards.

"nostdlib" Motivation & Purpose

nostdlib is a lightweight, minimalistic approach to C development that removes dependencies on the standard library. The motivation behind this project is to provide developers with greater control over their code by eliminating unnecessary overhead, reducing binary size, and enabling deployment in resource-constrained environments.

Many modern development environments rely heavily on the standard library, which, while convenient, introduces unnecessary bloat, security risks, and unpredictable dependencies. nostdlib aims to give developers fine-grained control over memory management, execution flow, and system calls by working directly with the underlying platform.

Benefits

Minimal overhead

By removing the standard library, nostdlib significantly reduces runtime overhead, allowing for faster execution and smaller binary sizes.

Increased security

Standard libraries often include unnecessary functions that increase the attack surface of an application. nostdlib mitigates security risks by removing unused and potentially vulnerable components.

Reduced binary size

Without linking to the standard library, binaries are smaller, making them ideal for embedded systems, bootloaders, and operating systems where storage is limited.

Enhanced performance

Direct control over system calls and memory management leads to performance gains by eliminating abstraction layers imposed by standard libraries.

Better portability

By relying only on fundamental system interfaces, nostdlib allows for easier porting across different platforms without worrying about standard library availability.