Standard Library Usage

A big goal of WallShell is to use as little of the standard library (libc) as possible, while still providing a feature-rich command line interface.

Compiling for POSIX or Windows based systems require the usage of some system specific headers. If this is a problem, you'll have to manually do CUSTOM_CONSOLE_SETUP (and CUSTOM_THREAD_WRAPPER if using threads). See this for more details.

• All standard library function calls are expected to work as specified in the ISO C99 standard.
  • glibc, musl, mlibc, and msvc's libc are guaranteed to work.

Note on MSVC

MSVC (the Microsoft C Compiler) "deprecates" many of the libc functions used, stating that they are not safe. This is irrelevent in WallShell. The contexts in which these functions are used ensure memory safety, including buffer bounds checks. WallShell disables warning 4996 (which tells you the functions are deprecated and prevents you from compiling), only for the wall_shell.c source file.

NOTE: The rest of this file is meant for freestanding environments. If you are not compiling for a freestanding environment, or rolling your own libc, ignore the rest of this file.

All functions and expected behavior can be found in at cppreference. Please note that WallShell expects the C99 versions of these functions. Listed below are the required headers & functions that are used from them.

Freestanding Headers

These headers should be provided by your compiler, and don't need to be manually created or added by your standard library:

• stdint.h
• stdbool.h
• stddef.h
• stdarg.h

Libc Headers

These headers/functions typically have to be defined by your standard library (or you) themselves.

string.h

• strtok
  • This is only needed if DISABLE_MALLOC is not defined. It typically uses malloc() internally.
• strlen
• strcmp
• strcpy
• memcpy
• memset

stdlib.h

If DISABLE_MALLOC is not defined

• malloc
• realloc

If DISABLE_MALLOC is defined

• Nothing (the header is still expected to exist, even if empty).

stdio.h

• fprintf
  • This is probably the biggest problem for freestanding environments without a standard lib.
  • A simple solution is to map this to printf, and define the following:
    • FILE
    • stdin
    • stdout
    • stderr
    • EOF
    • These definitions don't necessarily have to do anything, they just need to be defined.