# mulle-vararg Release on [github](//github.com/mulle-nat/mulle-vararg): [![Build Status](https://travis-ci.org/mulle-nat/mulle-vararg.svg?branch=release)](https://travis-ci.org/mulle-nat/mulle-vararg) A variable argument passing scheme written in C (C11). It's an alternative to [stdarg](//en.wikipedia.org/wiki/Stdarg.h) or [varargs](//pubs.opengroup.org/onlinepubs/7908799/xsh/varargs.h.html), but not compatible with either. #### Advantages * Easy to write in C, does not need compiler ABI internals to construct or read. You don't need [libffi](//sourceware.org/libffi/) or some such. * Cheap forwarding to other functions. #### Disadvantages * No compiler support - so far :) ## How it works **mulle-vararg** assumes that the arguments are not layed out in stack alignment fashion but like in a struct. The C promotion rules are still observed though. > Remember the C argument promotion rules are > > 1. char and short to int/unsigned int > 2. float to double > Let's assume there is a compiler that uses **mulle-vararg** for variable arguments. It collects **all** function parameters and packs them into a struct, then passes this struct to the function. A **printf** function being being called like this: ``` printf( "%d %f %lld\n", (char) 'x', (float) 0.2, 1848LL; ``` would get its arguments embedded in a struct like this ``` struct { char *format; struct { int value1; // standard char -> int promotion double value2; // standard float -> double promotion long long value3; } varargs; } _param; ``` **mulle-vararg** provides the necessary functions to read such a struct. It has no code to create it. ## API * [API](dox/API_VARARG.md) ## Install On OS X and Linux you can use [homebrew](//brew.sh), respectively [linuxbrew](//linuxbrew.sh) to install the library: ``` brew tap mulle-kybernetik/software brew install mulle-vararg ``` On other platforms you can use **mulle-install** from [mulle-build](//www.mulle-kybernetik.com/software/git/mulle-build) to install the library: ``` mulle-install --prefix /usr/local --branch release https://www.mulle-kybernetik.com/repositories/mulle-vararg ``` Otherwise read: * [How to Build](dox/BUILD.md) ### Platforms and Compilers All platforms and compilers supported by [mulle-c11](//www.mulle-kybernetik.com/software/git/mulle-c11/) ## Author [Nat!](//www.mulle-kybernetik.com/weblog) for [Mulle kybernetiK](//www.mulle-kybernetik.com) and [Codeon GmbH](//www.codeon.de)