ft_printf

C project · variadics, libc

printf rebuilt from scratch: chars, strings, pointers, decimals, unsigned and hex.

• 100/100grade
• 9conversions

The problem

Rebuild printf from libc from scratch.

What I built

• All nine conversions: %c %s %p %d %i %u %x %X %%.
• Variadic arguments with stdarg, and number-to-base printing for decimal and hex.

The hard part

Where the va_list lives. The first draft passed it by value to the function that handles each conversion, which works by accident on x86-64 Linux, but on an arm64 Mac each call reads from its own copy: %u %u %u with 1, 2, 3 prints 1 1 1, and %d %s reads the int back as a string pointer and crashes. The handler now takes a pointer, so every conversion moves the same list forward. %p with NULL prints (nil), as glibc does, where macOS prints 0x0.

Built with

• C
• stdarg
• Libft

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