How to make the PCC dump core

[Donn Seeley]

Almost no one rose to the bait when I issued a challenge to find the
shortest inputs that cause the Portable C Compiler to dump core.  I
don't know whether to be happy that the compiler is so robust or
disappointed that I won't get more experience fixing PCC bugs...

If this is a dull afternoon, you may be interested in examining the
'programs' I had in mind.  Here is the shortest string I could find
that could be compiled in the normal way to achieve a core dump with
the 4.2 BSD PCC on the VAX (note, no trailing newline):

	*1e38*2

This 7-byte 'program' causes a floating exception when the compiler
attempts to evaluate the constant expression '1e38 * 2', which of
course is outside the range of the VAX's D- and F- float arithmetic.
This bug can be fixed by arranging to catch SIGFPE and complaining when
it occurs; I can provide code on request.

A much shorter 'program' can be used to get a core dump if you allow me
to sneak past the preprocessor and provide input directly to the
compiler.  This exercise results in a short but suspenseful wait,
followed by a segmentation fault:

	echo -n '#' | /lib/ccom

There is a missing end-of-file check in mip/scan.c...  Again, code can
be supplied on request.  Neither of these bugs is so earthshaking that
we can't live with them, but they were fun to find and fix.

One last trick -- a short program to cause the compiler to go into an
infinite loop generating code (gets the error 'expression causes
compiler loop').  The amusing results can best be appreciated by
running:

	echo -n 'i=i*i' | /lib/ccom

Haven't tried fixing this one yet,

Donn Seeley    University of Utah CS Dept    donn at utah-cs.arpa
40 46' 6"N 111 50' 34"W    (801) 581-5668    decvax!utah-cs!donn