From: k3040e4 AT c210 DOT edvz DOT uni-linz DOT ac DOT at (Oberhumer Markus)
Message-Id: <199607251942.VAA25298@c210.edvz.uni-linz.ac.at>
Subject: bounds checking
To: djgpp-workers AT delorie DOT com (djgpp-workers)
Date: Thu, 25 Jul 1996 21:42:38 -0200 (MET DST)
Return-Read-To: markus DOT oberhumer AT jk DOT uni-linz DOT ac DOT at
Content-Type: text


===============================================================================
Markus F.X.J. Oberhumer <markus DOT oberhumer AT jk DOT uni-linz DOT ac DOT at>

Subject: bounds checking
To: djgpp-workers AT delorie DOT com
===============================================================================

Has someone of you tried to apply Richard W.M. Jones' bounds
checking patches to djgpp ?
I'm also using the emx package, and bounds checking has saved me
hours of work. It's a really valuable extension.

Markus


This is the readme that comes with emx + gcc 2.7.2:


Bounds Checking Patches for GCC 2.7.1
-------------------------------------

By Richard W.M. Jones <rwmj AT doc DOT ic DOT ac DOT uk>
Version: 1.0

What is bounds checking?
------------------------

These patches give very fine-grained bounds checking, catching errors in
C programs like this one:

	int i;
	char array[10];

	for (i = 0; i <= 10; ++i)
	  array[i] = 0;

(Notice element array[10] is not part of the array). The patches are
compatible with almost all C constructs. For instance, the following
programs have been successfully compiled with bounds checking:

	Tcl 7.3 & 7.4
	Tk 3.6 & 4.0
	Ghostscript 262
	uEmacs 3.10
	xrn
	GNU Grep 2.0
	XBoing 1.8

What files do you need?
-----------------------

You can install GCC with bounds checking either by compiling from the source,
or using one of the current binary distributions.

>> To compile from source, you need to retrieve:

	bounds-checking-2.7.1-x.y.tgz

   *plus* the source for GCC (which you may already have). One place you can
   find the source of GCC is:

	ftp://sunsite.doc.ic.ac.uk/gnu/

   You will need around 60 Mbytes of free disk space.

>> To install GCC binaries, you will need to retrieve:

	bounds-checking-2.7.1-x.y-binary-cpu-manufacturer-system.tgz

   (where cpu-manufacturer-system might be, for instance, `i486-unknown-linux')
   If you don't see a binary distribution for your particular machine, then
   you will need to compile from source (see above). You might consider
   sending me the binaries so I can put them on the FTP site.

   You do *not* need the source to GCC. You do *not* even need a C compiler.
   You will need a way of reading `info' files, though, if you want to read
   the supplied documentation.

How to compile GCC with bounds checking from source
---------------------------------------------------

Skip this section if you got a binary distribution.

Let's suppose, for the sake of example, that you've already placed a *fresh*
GCC source tree in `~/gcc-2.7.1'. Patch the tree as follows:

	cd ~/gcc-2.7.1
	make distclean			# Clean up source tree.
	zcat ~/bounds-checking-2.7.1-x.y.tgz | tar xvf -
	patch -p4 < bounds-checking.diff

Compile GCC as detailed in the file `INSTALL' that comes with GCC. Usually
you need to type:

	cd ~/gcc-2.7.1
	./configure			# Possibly some --options here.
	make

This also makes the bounds checking library (in the bounds/lib/ subdir.).
You'll need `makeinfo' (from the `texinfo' package) to make the info pages.

Installing a binary distribution
--------------------------------

To install in the directory `~/gcc-2.7.1' (for the sake of example), you
would do:

	mkdir ~/gcc-2.7.1
	cd ~/gcc-2.7.1
	zcat ~/bounds-checking-2.7.1-x.y-binary-cpu-mf-system.tgz | tar xvf -

Compile programs with bounds checking
-------------------------------------

Once you've got the program compiled, use the `-fbounds-checking' flag
to add bounds checking to your programs. Eg.

	~/gcc-2.7.1/xgcc -B~/gcc-2.7.1/ -fbounds-checking -c file1.c -o file1.o
	~/gcc-2.7.1/xgcc -B~/gcc-2.7.1/ -fbounds-checking file1.o -o program

Notice that:
  (1) I've assumed you have compiled/installed GCC in `~/gcc-2.7.1'.
  (2) You need to pass the `-B' option to tell GCC which directory you're
      using. Note that the directory needs a trailing `/'.

For Makefiles, you could add/change the following rules:

	GCC_HOME = $(HOME)/gcc-2.7.1
	CC = $(GCC_HOME)/xgcc
	CFLAGS = -B$(GCC_HOME)/ -fbounds-checking -g -Wall ..etc..

The first place to look for information is the GCC info page. The relevant
files are:

	~/gcc-2.7.1/gcc.info
	~/gcc-2.7.1/gcc.info-*

You will need `emacs', `tkinfo' or similar, to read them.

There is an old manual in PostScript form in the file:

	~/gcc-2.7.1/bounds/report/bcrep2.ps.gz

and the source for this (in M$-Word 6 format - yes, I know):

	~/gcc-2.7.1/bounds/report/bcrep2.doc.gz

Special cases for bounds checking
---------------------------------

Although bounds checking ought to be automatic, if you use one of the
following constructs, you may need to change your program:

    .   signal handlers
        threads
                Read the user manual. For signal handlers, you will need to
                move the signal handlers into unchecked code. There are
                hooks in the checking library for threads.
    .   <stdarg.h>
        <varargs.h>
                The `va_arg' macro does not work. You need to include
                `gcc-2.7.1/bounds/run-includes/fix-args.h' after including
                <stdarg.h> or <varargs.h>.
    .   Using `-2' as a pointer.
                You can't use `-2' as a special pointer representation (because
                I use it). To fix this, either change your code to use, say,
                -1, or change the definition of ILLEGAL in `bounds/lib/
                bounds-lib.h'.

Read the user manual for more details.

Bug reports
-----------

There are a few known bugs: read about them in

	~/gcc-2.7.1/bounds/BUGS

Please send bug reports & fixes to

	rwmj AT doc DOT ic DOT ac DOT uk

Related documents
-----------------

http://www-ala.doc.ic.ac.uk/~phjk/BoundsChecking.html
http://www-dse.doc.ic.ac.uk/~rj3/bounds-checking.html

Platforms
---------

We have tested the program on these platforms:

        Linux 1.2.13
        SunOS 4.1.3 (mark AT sgcs DOT com)
        ESIX SVR 4.0.4 on a 486 machine (herman AT htbrug DOT hobby DOT nl)
        OSF 2.0 on DEC Alpha (tuppa AT iue DOT tuwien DOT ac DOT at)
        Solaris (what version?)
        HPUX (what version?)

The extensions ought to run on any platform that supports GCC.