3 PDCLib - Public Domain C Library
4 ================================
9 Permission is granted to use, modify, and / or redistribute at will.
11 This includes removing authorship notices, re-use of code parts in
12 other software (with or without giving credit), and / or creating a
13 commercial product based on it.
15 This permission is not revocable by the author.
17 This software is provided as-is. Use it at your own risk. There is
18 no warranty whatsoever, neither expressed nor implied, and by using
19 this software you accept that the author(s) shall not be held liable
20 for any loss of data, loss of service, or other damages, be they
21 incidental or consequential. Your only option other than accepting
22 this is not to use the software at all.
24 A case for Public Domain
25 ------------------------
27 There was a time when you could just post a piece of code to usenet
28 and say, "I give it away for free; perhaps it's useful for you."
30 Then came the lawyers.
32 There are building blocks in software engineering that are so basic
33 that everyone should have free access to them without having to
34 employ a complete legal department for advice. They should be FREE.
35 Available for free, free of licensing implications, free of attached
36 propaganda, free of everything but their useful self.
38 Today, even the term "free" has to be defined by several paragraphs
41 Sick and tired of it, the author brought you this piece of software
42 under a "license" that should not be neccessary in the first place:
43 "Free" should have been enough.
45 Unfortunately, German law does not even *allow* to declare a work to
46 be "in the Public Domain", so the "free for all" license I intended
47 had to be made expressively.
52 This is a C Standard Library. Nothing more, nothing less. No POSIX
53 or other extensions, just what's defined in ISO/IEC 9899.
55 (Well, this is what it will be when the 1.0 release comes out. See
56 the "Development Status" section to see what's implemented so far.)
61 As a namespace convention, everything (files, typedefs, functions,
62 macros) not defined in ISO/IEC 9899 is prefixed with _PDCLIB.
63 The standard defines any identifiers starting with '_' and a capital
64 letter as reserved for the implementation, and since the chances of
65 your compiler using an identifier in the _PDCLIB range are slim,
66 any strictly conforming application should work with this library.
68 PDCLib consists of several parts:
71 2) implementation files for standard functions;
72 3) internal header files keeping complex stuff out of the standard
74 4) the central, platform-specific file _PDCLIB_config.h;
75 5) platform-specific implementation files;
76 6) platform-specific, optimized "overlay" implementations (optional).
78 The standard headers (in ./includes/) only contain what they are
79 defined to contain. Where additional logic or macro magic is
80 necessary, that is deferred to the internal files. This has been done
81 so that the headers are actually educational as to what they provide
82 (as opposed to how the library does it).
84 Note that there *might* be some feature to remove this additional
85 level of indirection for a production release, to ease the workload
86 put on the preprocessor.
88 There is a seperate implementation file (in ./function/{header}/) for
89 every function defined by the standard, named {function}.c. Not only
90 does this avoid linking in huge amounts of unused code when you use
91 but a single function, it also allows the optimization overlay to work
94 (The directory ./functions/_PDCLIB/ contains internal and helper
95 functions that are not part of the standard.)
97 Then there are internal header files (in ./internal/), which contain
98 all the "black magic" and "code fu" that was kept out of the standard
99 headers. You should not have to touch them if you want to adapt PDCLib
100 to a new platform. Note that, if you *do* have to touch them, I would
101 consider it a serious design flaw, and would be happy to fix it in the
102 next PDCLib release. Any adaption work should be covered by the steps
105 For adapting PDCLib to a new platform (the trinity of CPU, operating
106 system, and compiler), make a copy of ./platform/example/ named
107 ./platform/{your_platform}/, and modify the files of your copy to suit
108 the constraints of your platform. When you are done, copy the contents
109 of your platform directory over the source directory structure
110 of PDCLib (or link them into the appropriate places). That should be
111 all that is actually required to make PDCLib work for your platform.
113 Of course, your platform might provide more efficient replacements
114 for the generic implementations offered by PDCLib. The math functions
115 are an especially "juicy" target for optimization - while PDCLib does
116 provide generic implementations for each of them, there are usually
117 FPU opcodes that do the same job, only orders of magnitude faster. For
118 this, you might want to create an "optimization overlay" for PDCLib.
123 The basic idea of PDCLib is to provide a generic implementation that
124 is useable even on platforms I have never heard of - for example, the
125 OS and/or compiler *you* just wrote and now need a C library for. That
126 is actually what PDCLib was written for: To provide a C library for
127 compiler and OS builders that do not want the usual baggage of POSIX
128 and GNU extensions, licensing considerations etc. etc.
130 Thus, PDCLib provides generic implementations. They do work, and do
131 so correctly, but they are not very efficient when compared to hand-
132 crafted assembler or compiler build-ins. So I wanted to provide a
133 means to modify PDCLib to run more efficiently on a given platform,
134 without cluttering the main branch with tons of #ifdef statements and
135 "featureset #defines" that grow stale quickly.
137 The solution is the "optimization overlay". Every function has its
138 own implementation file, which makes it possible to replace them
139 piecemeal by copying a platform-specific overlay over the main PDCLib
140 branch to create a PDCLib adapted / optimized for the platform in
141 question. That overlay could be part of the PDCLib source tree (for
142 established platforms where maintainers won't bother with PDCLib), or
143 part of that platform's source tree (for under-development platforms
144 PDCLib maintainers won't bother with).
146 So, to use PDCLib on your given platform, you unpack PDCLib (as you
147 obviously have done already since you are reading this), and copy
148 the overlay for your platform over the PDCLib source tree structure.
154 Freestanding-only C99 implementation without any overlay, and missing
155 the INTN_C() / UINTN_C() macros. <float.h> still has the enquire.c
156 values hardcoded into it; not sure whether to include enquire.c in the
157 package, to leave <float.h> to the overlay, or devise some parameterized
158 macro magic as for <limits.h> / <stdint.h>. Not thoroughly tested, but
159 I had to make the 0.1 release sometime so why not now.
162 Adds implementations for <string.h> (excluding strerror()), INTN_C() /
163 UINTN_C() macros, and some improvements in the internal headers.
164 Test drivers still missing, but added warnings about that.
167 Adds test drivers, fixes some bugs in <string.h>.
170 Implementations for parts of <stdlib.h>. Still missing are the floating
171 point conversions, and the wide-/multibyte-character functions.
174 With v0.5 (<stdio.h>) taking longer than expected, v0.4.1 was set up as
175 a backport of bugfixes in the current development code.
176 - #1 realloc( NULL, size ) fails (fixed)
177 - #2 stdlib.h - insufficient documentation (fixed)
178 - #4 Misspelled name in credits (fixed)
179 - #5 malloc() splits off too-small nodes (fixed)
180 - #6 qsort() stack overflow (fixed)
181 - #7 malloc() bug in list handling (fixed)
182 - #8 strncmp() does not terminate at '\0' (fixed)
183 - #9 stdint.h dysfunctional (fixed)
184 - #10 NULL redefinition warnings (fixed)
187 Implementations for <inttypes.h>, <errno.h>, most parts of <stdio.h>,
188 and strerror() from <string.h>.
189 Still no locale / wide-char support. Enabled all GCC compiler warnings I
190 could find, and fixed everything that threw a warning. (You see this,
191 maintainers of Open Source software? No warnings whatsoever. Stop telling
192 me it cannot be done.) Fixed all known bugs in the v0.4 release.
195 A WORD ON THE v0.5 RELEASE
196 ==========================
198 The v0.5 release is not well-tested. There are several things in it done
199 in a way that I would never label "release quality". Some things are not
200 even in the *structure* I would like them to be. An example for this is
201 the current handling of errno values: It needlessly introduces dependency
202 on PDCLib (because I use non-standard values), and the values are placed
203 in the wrong header (_PDCLIB_int.h instead of _PDCLIB_glue.h where they
204 would be more appropriate).
206 But at some point during the development toward the v0.5 release, I found
207 that my current PDCLib work schedule simply does not allow me to wait
208 until every piece of <stdio.h> is as I would like it to be. It would
209 probably take another year or two, and my patience is UP.
211 I want this released, and I want to think about something else but
212 <stdio.h> for some time.
214 So, expect significant change to how stdio is done in upcoming releases.
215 Everything *WILL* be stable by the time v1.0 comes around, but until then
216 you will have to accept that I can only deliver "hobby quality" for now.
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