Humbleness of comp.lang.c folks

June 26, 2013 at 4:06 pm | Posted in Programming | Leave a comment
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I mostly hang on comp.lang.c and sometime discussion go deep into technical details of C language while solving a current problem. At comp.lang.c, folks do not go into details for the sake of details but to solve a particular problem. I got stuck in some issue and was continuously referring to comp.lang.c and then to K&R2 and then to H&S5 and I discovered one error in H&S 5. Actually I did not even know this till Keith Thompson credited and mailed me on the discovery (he mailed Harbison too). You can get the original post at googlegroups or velocityreviews . I thought it is better if I share his kind and humble words here on my blog (I am kind of quite late to post this but better late than never 🙂 ) :

Credit for finding this error goes to Arnuld Uttre, whom I’ve cc’ed on this e-mail (if I got his address right). It came up in a discussion on comp.lang.c, subject “strtoul() behavior”.

I have a first printing of H&S 5. On page 413, in the discussion of thestrto*() functions, it says (any typos are mine):

If no conversion is possible because the string does not match the expected number model (or is empty), then zero is returned, *ptr is set to the value of str, and errno is set to ERANGE.

In fact, errno is not set in this case. See C99

If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.

A quick experiment with one implementation shows that errno is in fact left as 0.

(A very small quibble: though the previous page mentions that ptr is ignored if it’s null, it might be worth changing “*ptr is set to …” to “*ptr (if it’s non-null) is set to …”. This is not actually necessary, but in my opinion it would make it slightly clearer.Feel free to ignore this.)

Copyright © 2013 Arnuld Uttre, Village – Patti, P.O – Manakpur, Tehsil – Nangal, Distt. – Ropar, Punjab (INDIA).

Verbatim copying and distribution of this entire article are permitted worldwide, without royalty, in any medium, provided this notice, and the copyright notice, are preserved.


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