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Full Discussion: Some questions regarding old if.c
Top Forums Programming Some questions regarding old if.c Post 302930272 by achenle on Thursday 1st of January 2015 12:35:50 PM
Old 01-01-2015
The source code is old K&R C, without function declarations.

Don't write code like that, and don't ever modify old K&R C by adding function declarations - unless you like getting into the intricacies and implications of C variable promotion rules, and how they may have changed over the years.

Original K&R C just took all arguments to a function, promoted them so they'd all be the same size, and stuffed them on the stack.

I think, if arguments aren't declared after the first function definition line:
Code:
main(argc, argv) <--defintion
char *argv[];  <-- argument declaration
{
    ....

then the argument implicitly defaults to "int".

Basically, in K&R C all functions are called as variable argument functions with every argument promoted to the same size, and the arguments aren't type-checked. Ever. And argument declarations in the function definitions only tell the function how to interpret the data in the variable passed - whatever that value may be, with, again, no type checking.

A "declaration" is code that tells the compiler what something is - think of it as a customs declaration for a bottle of booze - you're telling customs that you have a bottle of booze somewhere in your luggage, and what it is. It's not the bottle itself.

A "definition" is code that IS the function or variable. It's the bottle itself.

K&R C has pretty much no declarations. No one knows what anything else is. Try making drinks without knowing in advance what's in every bottle of booze...
Last edited by achenle; 01-01-2015 at 01:47 PM..
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LEARN ABOUT OSX

kc

KC(1)							      General Commands Manual							     KC(1)

NAME

       kc - generate C code from Kimwitu input

SYNOPSIS

       kc [ file.k ...	]
       kc --version

DESCRIPTION

       kc reads the abstract syntax definition, function definitions, rewrite rules and unparse rules from the files given on the command line, or
       from the standard input if no file arguments were given, and generates for each file.k input file a pair of file.c and a file.h files  that
       contain	the  translation  of  the  functions  defined  in  the	corresponding  file.k, in addition to the files that are always generated:
       csgiok.[ch], rk.[ch] and unpk.[ch] files, that contain respectively the CSGIO-, the rewrite- and the unparse-functions, and the k.c and k.h
       files  that contain the grammar tables and the remaining `default' functions.  If no command line file arguments are given, the translation
       of the user-defined functions will be generated in stdin.[ch] files.

       kc does not unnecessarily overwrite a file: if a file would be overwritten with its own (identical) contents, it will not be touched.  This
       makes it easy to write an efficient Makefile.

OPTIONS

       --version   print the version number of kc and exit (this option is not available in kc versions older than V3_9P3)

GENERATED FILES

       k.[ch]	   the grammar and default functions

       rk.[ch]	   the rewrite view declarations and rewrite functions

       csgiok.[ch] the CSGIO functions

       unpk.[ch]   the unparse view declarations and unparsing functions

       file.[ch]   translation of user-provided Kimwitu functions.

       stdin.[ch]  translation of user-provided Kimwitu functions if no command line file arguments were given.

DIAGNOSTICS

       If  an  error  is  encountered in the Kimwitu input, an apropriate error message will be written on standard error, code generation will be
       suppressed and a non-zero exit value will be returned.  The error messages should be self-explanatory.

AUTHOR

       Axel Belinfante, University of Twente, the Netherlands.

CONTACT

       By Email: <kimwitu@cs.utwente.nl>

VERSION

       This manual page documents kc V3_* and newer.

								   May 13, 1996 							     KC(1)
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