unproto1

Usage

Package

unproto

Overview

This document describes a filter that sits in between the UNIX C preprocessor and the next UNIX C compiler stage, on the fly rewriting ANSI-style syntax to old-style syntax. Typically, the program is invoked by the native UNIX C compiler as an alternate preprocessor. The unprototyper in turn invokes the native C preprocessor and massages its output. Similar tricks can be used with the lint(1) command.

Language constructs that are always rewritten:

function headings, prototypes, pointer types

ANSI-C style function headings, function prototypes, function pointer types and type casts are rewritten to old style. <stdarg.h> support is provided for functions with variable-length argument lists.

character and string constants

The \a and \x escape sequences are rewritten to their (three-digit) octal equivalents.

Multiple string tokens are concatenated; an arbitrary number of whitespace or comment tokens may appear between successive string tokens.

Within string constants, octal escape sequences are rewritten to the three-digit \ddd form, so that string concatenation produces correct results.

date and time

The __DATE__ and __TIME__ tokens are replaced by string constants of the form "Mmm dd yyyy" and "hh:mm:ss", respectively. The result is subjected to string concatenation, just like any other string constant.

Language constructs that are rewritten only if the program has been configured to do so:

void types

The unprototyper can be configured to rewrite "void *" to "char *", and even to rewrite plain "void" to "int". These features are configurable because many traditional UNIX C compilers do not need them.

Note: (void) argument lists are always replaced by empty ones.

ANSI C constructs that are not rewritten because the traditional UNIX C preprocessor provides suitable workarounds:

const and volatile

Use the "-Dconst=" and/or "-Dvolatile=" preprocessor directives to get rid of unimplemented keywords.

token pasting and stringizing

The traditional UNIX C preprocessor provides excellent alternatives. For example:

#define string(bar)     "bar"           /* instead of: # x */
#define paste(x,y)      x/**y         /* instead of: x##y */

There is a good reason why the # and ## operators are not implemented in the unprototyper. After program text has gone through a non-ANSI C preprocessor, all information about the grouping of the operands of # and ## is lost. Thus, if the unprototyper were to perform these operations, it would produce correct results only in the most trivial cases. Operands with embedded blanks, operands that expand to null tokens, and nested use of # and/or ## would cause all kinds of obscure problems.

Unsupported ANSI features:

trigraphs and #pragmas

Trigraphs are useful only for systems with broken character sets. If the local compiler chokes on #pragma, insert a blank before the "#" character, and enclose the offending directive between #ifdef and #endif.

Files

/wherever/stdarg.h, provided with the unproto filter.

Diagnostics

Problems are reported on the standard error stream. A non-zero exit status means that there was a problem.

Author(s)

Wietse Venema ([email protected])
Eindhoven University of Technology
Department of Mathematics and Computer Science
Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

Last modification

93/06/18 22:29:37

Version/release

1.6