Goto-Be-Gone

gbg is a python program that partially implements the goto-removal algorithm from Taming Control Flow: A Structured Approach to Eliminating Goto Statements using a modified pycparser library.

It reads in a C file, searches for a function, prints the function, eliminates the gotos that it can, then prints the function post-removal.

See implementation notes here.

Setup

The implementation relies on a slightly modified version of the pycparser library. A virtualenv will need to be setup in the directory of the project.

$ virtualenv .
$ source ./env/bin/activate
$ (env) pip3 install ./pycparser

This should get it up and running if you're in the virtualenv.

Usage

./parse.py infile [function]

Supported

• Sibling removal
• Outwards transformations
• Inwards transformations

Not Supported

• Unconditional gotos

A conditional goto is if (cond) goto foo. Wrap unconditionals in if (true). Hopefully this will be a part of the implementation.

• Statements directly "under" a label

// The if statement is directly "under" the label, so this won't work.
bad:
    if (cond) {
        if (jump()) goto bad;
    }

// No gotos are under the label, so this is fine.
good:
    foo();
    if (cond) {
        if (jump()) goto good;
    }

• Indirectly related nodes

• Nested inwards transformations