edski@phx.mcd.mot.com (Ed Skinner) (10/11/90)
Do you have a trick or two for polishing and/or debugging "C"
code using typical Unix(tm) tools? I am interested in anything that
helps locate coding errors, particularly those techniques that use
programs available on run-of-the-mill Unix-based systems.
I am making a collection and will post it to the net. Please mail
your submissions instead of posting them to this group.
Here is an example of what I'm looking for;
I use cb(1) and diff(1) to catch what I'll call grouping or indentation
problems. I fall into this trap when my first version of code has a single
statement inside an if-statement's true clause and then I later go back and
add another line or two of code.
fragment()
{
if (moveit(datap, dev) == 0)
assert(dvcp->c_res == 0); <----- ADDED LINE
if (dvcp->c_flags & ASYNC) {
status = q_send(dvcp->c_id, &end);
assert((status == E_NOERR) || (status == E_OBJDEL));
}
}
Both versions will compile and lint(1) (in the full version, not the
fragment I've shown above) without detecting the error. Visually, the
second if-statement version is within the first if-statement's true clause.
However, the compiler ignores indentation and generates the second
if-statement code completely outside of the first.
I recently spent two days tracking down one of these errors!
"Fool me once, shame on you [the compiler]. Fool me twice, shame on me!"
Using cb(1) and diff(1), I developed a quick check that will find
this type of error.
Briefly, the source file is "beautified" and compared to the original.
Any differences, such as in the amount of indentation I think is necessary
versus what cb(1) thinks is needed are pointed out by diff(1).
cb $f | diff - $f
One drawback, of course, is that the source file must be coded in
a cb(1) format in order to use cb(1) to "find" differences between what
I mean and what the compiler will understand. This format may not conform
with your favorite style, nor that of your employer. However, I am willing
to change my habits (and style) when I find something that will help me
generate better code in less time.
--
"Wisdom is the absence of ideals." Chinese proverb
#include <disclaimer.h>
Ed Skinner, Technical Training, Motorola Inc., MicroComputer Division
2900 S Diablo Way, Tempe Az 85282, USA (602)438-3956
Internet: edski@phx.mcd.mot.com, UUCPnet: noao!asuvax!mcdphx!edski