=== The 10 Commandments for C Programmers ===
by Henry Spencer (ANSI C version)
(Rule 9 is relaxed for VSTa)
------
The Ten Commandments for C Programmers
(Annotated Edition)
by Henry Spencer
1. Thou shalt run lint frequently and study its pronouncements with
care, for verily its perception and judgement oft exceed thine.
This is still wise counsel, although many modern compilers
search out many of the same sins, and there are often problems
with lint being aged and infirm, or unavailable in strange
lands. There are other tools, such as Saber C, useful to
similar ends.
'Frequently' means thou shouldst draw thy daily guidance from
it, rather than hoping thy code will achieve lint's blessing by
a sudden act of repentance at the last minute. De-linting a
program which has never been linted before is often a cleaning
of the stables such as thou wouldst not wish on thy worst
enemies. Some observe, also, that careful heed to the words of
lint can be quite helpful in debugging.
'Study' doth not mean mindless zeal to eradicate every byte
of lint output-if for no other reason, because thou just canst
not shut it up about some things-but that thou should know the
cause of its unhappiness and understand what worrisome sign it
tries to speak of.
2. Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end.
Clearly the holy scriptures were mis-transcribed here, as the
words should have been 'null pointer', to minimize confusion
between the concept of null pointers and the macro NULL (of
which more anon). Otherwise, the meaning is plain. A null
pointer points to regions filled with dragons, demons, core
dumps, and numberless other foul creatures, all of which
delight in frolicing in thy program if thou disturb their
sleep. A null pointer doth not point to a 0 of any type,
despite some blasphemous old code which impiously assumes this.
3. Thou shalt cast all function arguments to the expected type if they
are not of that type already, even when thou art convinced that
this is unnecessary, lest they take cruel vengeance upon thee
when thou least expect it.
A programmer should understand the type structure of his
language, lest great misfortune befall him. Contrary to the
heresies espoused by some of the dwellers on the Western Shore,
`int' and `long' are not the same type. The moment of their
equivalence in size and representation is short, and the agony
that awaits believers in their interchangeability shall last
forever and ever once 64-bit machines become common.
Also, contrary to the beliefs common among the more backward
inhabitants of the Polluted Eastern Marshes, `NULL' does not
have a pointer type, and must be cast to the correct type
whenever it is used as a function argument.
(The words of the prophet Ansi, which permit NULL to be defined
as having the type `void *', are oft taken out of context and
misunderstood. The prophet was granting a special dispensation
for use in cases of great hardship in wild lands. Verily, a
righteous program must make its own way through the Thicket Of
Types without lazily relying on this rarely-available
dispensation to solve all its problems. In any event, the great
deity Dmr who created C hath wisely endowed it with many types
of pointers, not just one, and thus it would still be necessary
to convert the prophet's NULL to the desired type.)
It may be thought that the radical new blessing of
'prototypes' might eliminate the need for caution about
argument types. Not so, brethren. Firstly, when confronted with
the twisted strangeness of variable numbers of arguments, the
problem returns... and he who has not kept his faith strong by
repeated practice shall surely fall to this subtle trap.
Secondly, the wise men have observed that reliance on
prototypes doth open many doors to strange errors, and some
indeed had hoped that prototypes would be decreed for purposes
of error checking but would not cause implicit conversions.
Lastly, reliance on prototypes causeth great difficulty in the
Real World today, when many cling to the old ways and the old
compilers out of desire or necessity, and no man knoweth what
machine his code may be asked to run on tomorrow.
4. If thy header files fail to declare the return types of thy library
functions, thou shalt declare them thyself with the most
meticulous care, lest grievous harm befall thy program.
The prophet Ansi, in her wisdom, hath added that thou shouldst
also scourge thy Suppliers, and demand on pain of
excommunication that they produce header files that declare
their library functions. For truly, only they know the precise
form of the incantation appropriate to invoking their magic in
the optimal way.
The prophet hath also commented that it is unwise, and leads
one into the pits of damnation and subtle bugs, to attempt to
declare such functions thyself when thy header files do the job
right.
5. Thou shalt check the array bounds of all strings (indeed, all
arrays), for surely where thou typest 'foo' someone someday
shall type 'supercalifragilisticexpialidocious'.
As demonstrated by the deeds of the Great Worm, a consequence
of this commandment is that robust production software should
never make use of gets(), for it is truly a tool of the Devil.
Thy interfaces should always inform thy servants of the bounds
of thy arrays, and servants who spurn such advice or quietly
fail to follow it should be dispatched forthwith to the Land Of
Rm, where they can do no further harm to thee.
6. If a function be advertised to return an error code in the event of
difficulties, thou shalt check for that code, yea, even though
the checks triple the size of thy code and produce aches in thy
typing fingers, for if thou thinkest 'it cannot happen to
me', the gods shall surely punish thee for thy arrogance.
All true believers doth wish for a better error-handling
mechanism, for explicit checks of return codes are tiresome in
the extreme and the temptation to omit them is great. But until
the far-off day of deliverance cometh, one must walk the long
and winding road with patience and care, for thy Vendor, thy
Machine, and thy Software delight in surprises and think
nothing of producing subtly meaningless results on the day
before thy Thesis Oral or thy Big Pitch To The Client.
Occasionally, as with the ferror() feature of stdio, it is
possible to defer error checking until the end when a
cumulative result can be tested, and this often produceth code
which is shorter and clearer. Also, even the most zealous
believer should exercise some judgement when dealing with
functions whose failure is totally uninteresting... but beware,
for the cast to void is a two-edged sword that sheddeth thine
own blood without remorse.
7. Thou shalt study thy libraries and strive not to reinvent them
without cause, that thy code may be short and readable and thy
days pleasant and productive.
Numberless are the unwashed heathen who scorn their libraries
on various silly and spurious grounds, such as blind worship of
the Little Tin God (also known as 'Efficiency'). While it is
true that some features of the C libraries were ill-advised, by
and large it is better and cheaper to use the works of others
than to persist in re-inventing the square wheel. But thou
should take the greatest of care to understand what thy
libraries promise, and what they do not, lest thou rely on
facilities that may vanish from under thy feet in future.
8. Thou shalt make thy program's purpose and structure clear to thy
fellow man by using the One True Brace Style, even if thou
likest it not, for thy creativity is better used in solving
problems than in creating beautiful new impediments to
understanding.
These words, alas, have caused some uncertainty among the
novices and the converts, who knoweth not the ancient wisdoms.
The One True Brace Style referred to is that demonstrated in
the writings of the First Prophets, Kernighan and Ritchie.
Often and again it is criticized by the ignorant as hard to
use, when in truth it is merely somewhat difficult to learn,
and thereafter is wonderfully clear and obvious, if perhaps a
bit sensitive to mistakes.
While thou might think that thine own ideas of brace style lead
to clearer programs, thy successors will not thank thee for it,
but rather shall revile thy works and curse thy name, and word
of this might get to thy next employer. Many customs in this
life persist because they ease friction and promote
productivity as a result of universal agreement, and whether
they are precisely the optimal choices is much less important.
So it is with brace style.
As a lamentable side issue, there has been some unrest from the
fanatics of the Pronoun Gestapo over the use of the word
'man' in this Commandment, for they believe that great
efforts and loud shouting devoted to the ritual purification of
the language will somehow redound to the benefit of the
downtrodden (whose real and grievous woes tendeth to get lost
amidst all that thunder and fury). When preaching the gospel to
the narrow of mind and short of temper, the word 'creature'
may be substituted as a suitable pseudoBiblical term free of
the taint of Political Incorrectness.
9. Thy external identifiers shall be unique in the first six
characters, though this harsh discipline be irksome and the
years of its necessity stretch before thee seemingly without
end, lest thou tear thy hair out and go mad on that fateful day
when thou desirest to make thy program run on an old system.
Though some hasty zealots cry 'not so; the Millenium is come,
and this saying is obsolete and no longer need be supported',
verily there be many, many ancient systems in the world, and it
is the decree of the dreaded god Murphy that thy next
employment just might be on one. While thou sleepest, he
plotteth against thee. Awake and take care.
It is, note carefully, not necessary that thy identifiers be
limited to a length of six characters. The only requirement
that the holy words place upon thee is uniqueness within the
first six. This often is not so hard as the belittlers
claimeth.
10. Thou shalt foreswear, renounce, and abjure the vile heresy which
claimeth that 'All the world's a VAX', and have no commerce
with the benighted heathens who cling to this barbarous belief,
that the days of thy program may be long even though the days
of thy current machine be short.
This particular heresy bids fair to be replaced by 'All the
world's a Sun' or 'All the world's a 386' (this latter being
a particularly revolting invention of Satan), but the words
apply to all such without limitation. Beware, in particular, of
the subtle and terrible 'All the world's a 32-bit machine',
which is almost true today but shall cease to be so before thy
resume grows too much longer.