PDCLib - Public Domain C Library ================================ License ------- PDCLib is distributed unter the Creative Commons CC0 License. You should have received a copy of the full legal text of this license as part of this distribution (COPYING.CC0). It is also available at https://creativecommons.org/publicdomain/zero/1.0/legalcode The following is a human-readable summary of that license. No Copyright The person who associated a work with this deed has dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission. See Other Information below. Other Information In no way are the patent or trademark rights of any person affected by CC0, nor are the rights that other persons may have in the work or in how the work is used, such as publicity or privacy rights. Unless expressly stated otherwise, the person who associated a work with this deed makes no warranties about the work, and disclaims liability for all uses of the work, to the fullest extent permitted by applicable law. When using or citing the work, you should not imply endorsement by the author or the affirmer. What is it ---------- This is a C Standard Library. Nothing more, nothing less. No POSIX or other extensions, just what's defined in ISO/IEC 9899. (Well, this is what it will be when the 1.0 release comes out. See the "Development Status" section to see what's implemented so far.) Internals --------- As a namespace convention, everything (files, typedefs, functions, macros) not defined in ISO/IEC 9899 is prefixed with _PDCLIB. The standard defines any identifiers starting with '_' and a capital letter as reserved for the implementation, and since the chances of your compiler using an identifier in the _PDCLIB range are slim, any strictly conforming application should work with this library. PDCLib consists of several parts: 1) standard headers; 2) implementation files for standard functions; 3) internal header files keeping complex stuff out of the standard headers; 4) the central, platform-specific file _PDCLIB_config.h; 5) platform-specific implementation files; 6) platform-specific, optimized "overlay" implementations (optional). The standard headers (in ./include/) only contain what they are defined to contain. Where additional logic or macro magic is necessary, that is deferred to the internal files. This has been done so that the headers are actually educational as to what they provide (as opposed to how the library does it). There is a seperate implementation file (in ./function/{header}/) for every function defined by the standard, named {function}.c. Not only does this avoid linking in huge amounts of unused code when you use but a single function, it also allows the optimization overlay to work (see below). (The directory ./functions/_PDCLIB/ contains internal and helper functions that are not part of the standard.) Then there are internal header files (in ./include/pdclib/), which contain all the "black magic" and "code fu" that was kept out of the standard headers. You should not have to touch them if you want to adapt PDCLib to a new platform. Note that, if you *do* have to touch them, I would consider it a serious design flaw, and would be happy to fix it in the next PDCLib release. Any adaption work should be covered by the steps detailed below. For adapting PDCLib to a new platform (the trinity of CPU, operating system, and compiler), make a copy of ./platform/example/ named ./platform/{your_platform}/, and modify the files of your copy to suit the constraints of your platform. When you are done, copy the contents of your platform directory over the source directory structure of PDCLib (or link them into the appropriate places). That should be all that is actually required to make PDCLib work for your platform. Of course, your platform might provide more efficient replacements for the generic implementations offered by PDCLib. The math functions are an especially "juicy" target for optimization - while PDCLib does provide generic implementations for each of them, there are usually FPU opcodes that do the same job, only orders of magnitude faster. For this, you might want to create an "optimization overlay" for PDCLib. Optimization Overlay -------------------- The basic idea of PDCLib is to provide a generic implementation that is useable even on platforms I have never heard of - for example, the OS and/or compiler *you* just wrote and now need a C library for. That is actually what PDCLib was written for: To provide a C library for compiler and OS builders that do not want the usual baggage of POSIX and GNU extensions, licensing considerations etc. etc. Thus, PDCLib provides generic implementations. They do work, and do so correctly, but they are not very efficient when compared to hand- crafted assembler or compiler build-ins. So I wanted to provide a means to modify PDCLib to run more efficiently on a given platform, without cluttering the main branch with tons of #ifdef statements and "featureset #defines" that grow stale quickly. The solution is the "optimization overlay". Every function has its own implementation file, which makes it possible to replace them piecemeal by copying a platform-specific overlay over the main PDCLib branch to create a PDCLib adapted / optimized for the platform in question. That overlay could be part of the PDCLib source tree (for established platforms where maintainers won't bother with PDCLib), or part of that platform's source tree (for under-development platforms PDCLib maintainers won't bother with). So, to use PDCLib on your given platform, you unpack PDCLib (as you obviously have done already since you are reading this), and copy the overlay for your platform over the PDCLib source tree structure. Development Status ------------------ Note that pre-v1.0 "releases" are internal milestones only, and that you are strongly encouraged to use the latest source snapshot at all times. v0.1 - 2004-12-12 Freestanding-only C99 implementation without any overlay, and missing the INTN_C() / UINTN_C() macros. <float.h> still has the enquire.c values hardcoded into it; not sure whether to include enquire.c in the package, to leave <float.h> to the overlay, or devise some parameterized macro magic as for <limits.h> / <stdint.h>. Not thoroughly tested, but I had to make the 0.1 release sometime so why not now. v0.2 - 2005-01-12 Adds implementations for <string.h> (excluding strerror()), INTN_C() / UINTN_C() macros, and some improvements in the internal headers. Test drivers still missing, but added warnings about that. v0.3 - 2005-11-21 Adds test drivers, fixes some bugs in <string.h>. v0.4 - 2005-02-06 Implementations for parts of <stdlib.h>. Still missing are the floating point conversions, and the wide-/multibyte-character functions. v0.4.1 - 2006-11-16 With v0.5 (<stdio.h>) taking longer than expected, v0.4.1 was set up as a backport of bugfixes in the current development code. - #1 realloc( NULL, size ) fails (fixed) - #2 stdlib.h - insufficient documentation (fixed) - #4 Misspelled name in credits (fixed) - #5 malloc() splits off too-small nodes (fixed) - #6 qsort() stack overflow (fixed) - #7 malloc() bug in list handling (fixed) - #8 strncmp() does not terminate at '\0' (fixed) - #9 stdint.h dysfunctional (fixed) - #10 NULL redefinition warnings (fixed) v0.5 - 2010-12-22 Implementations for <inttypes.h>, <errno.h>, most parts of <stdio.h>, and strerror() from <string.h>. Still no locale / wide-char support. Enabled all GCC compiler warnings I could find, and fixed everything that threw a warning. (You see this, maintainers of Open Source software? No warnings whatsoever. Stop telling me it cannot be done.) Fixed all known bugs in the v0.4 release.