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Man Pages


Manual Reference Pages  -  COCOR (1)

NAME

cocor - Compiler generator generator

CONTENTS

Synopsis
Description
Options
Grammar Tests
Bugs

SYNOPSIS

cocor filename.atg [ options ]...

DESCRIPTION

cocor reads a specification from filename.atg and generate a compiler ( scanner, parser and main module )

OPTIONS

-C Generate complete compiler driving module, including source listing featuring interleaved error message reporting. To use this option the file COMPILER.FRM (or <grammar>.FRM ) must be available.

-D Generate Source line number (#line) for each semantic action. This causes the semantic actions in the generated C program to be labelled with reference to the original .ATG file, so that one can use a symbolic debugger on the .ATG file.

-L (Listing) Force listing (Normally the listing of the grammar is suppressed if the compilation is error free).

-P (Parser only) Suppress generation of the scanner. As with the regeneration of the definition modules, regeneration of the scanner is often tedious, and results in no changes from the one first generated. This option must be used with care. It can also be used if a hand crafted scanner is to be supplied (see the notes on the use of hand crafted scanners in the file COCOL).

-T (Tests) Suppress Generation of Scanner and Parser. (If this option is exercised, the generation of the scanner and parser is suppressed, but the attributed grammar is parsed and checked for grammatical inconsistencies, LL(1) violations and so on).

The following options are really intended to help with debugging/teaching applications. Their effect may best be seen by judicious experimentation.

-A Trace automaton

-F Give Start and Follower sets for each non-terminal in the grammar

-G Print top-down graph

-S Print symbol table

When using Coco/R, the frame files SCAN_C.FRM and SCAN_H.FRM and PARSER_C.FRM and PARSER_H.FRM must exist in the current directory, or in the directories specified by the environment variable CRFRAMES.

GRAMMAR TESTS

Coco/R performs several tests to check if the grammar is well-formed. If one of the following error messages is produced, no compiler parts are generated.

NO PRODUCTION FOR X
The nonterminal X has been used, but there is no production for it.

X CANNOT BE REACHED
There is a production for nonterminal X, but X cannot be derived from the start symbol.

X CANNOT BE DERIVED TO TERMINALS
For example, if there is a production


X = "(" X ")" .
X = Y.
Y = X.

X and Y are nonterminals with circular derivations.

TOKENS X AND Y CANNOT BE DISTINGUISHED
The terminal symbols X and Y are declared to have the same structure,

e.g.:
integer = digit { digit } .
real = digit { digit } ["." { digit } ].

In this example, a digit string appears ambiguously to be recognized as an integer or as a real.

The following messages are warnings. They may indicate an error but they may also describe desired effects. The generated compiler parts may still be valid. If an LL(1) error
is reported for a construct X , one must be aware that the generated parser will choose the first of several possible alternatives for X.

X NULLABLE
X can be derived to the empty string, e.g. X = { Y } .

LL(1) ERROR IN X:Y IS START OF MORE THAN ONE ALTERNATIVE
Several alternatives in the production of X start with the terminal Y
e.g.:
Statement = ident ":=" Expression
| ident [ ActualParameters ] .

LL(1) ERROR IN X:Y IS START AND SUCCESSOR OF NULLABLE STRUCTURE
Nullable structures are [ ... ] and { ... }
e.g.:
qualident = [ ident "." ] ident .
Statement = "IF" Expression "THEN" Statement
[ "ELSE" Statement ] .

The ELSE at the start of the else part may also be a successor of a statement. This LL(1) conflict is known under the name dangling else .

SEE ALSO

Moessenboeck, H., A Generator for Fast Compiler Front-Ends. Report 127, Dept. Informatik, ETH Zurich (1990)

Moessenboeck, H., A generator for production quality compilers. Proc 3rd Int’l Workshop on Compiler-Compilers, Schwerin FRG, 1990

BUGS

Mail bug reports to:

C Version: Frankie Arzu (farzu@uvg.edu.gt)

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