Re: (int)sizeof in smtpd

[Alexandre Ratchov]

On Thu, May 08, 2014 at 12:35:56PM -0400, Ted Unangst wrote:
 This is wrong in several ways.
 
 Never cast sizeof down, always cast the comparison variable up.
 
 I'll specifically call out this change:
 
 - if (snprintf(buf, sizeof(buf)) = (int)sizeof(buf))
 + if ((size_t)snprintf(buf, sizeof(buf)) = sizeof(buf))
 

note that the = operator promotes int to size_t, which makes the
cast useless and could permit lines to be shortened.

Re: (int)sizeof in smtpd

[Franco Fichtner]

On 08 May 2014, at 18:43, Alexandre Ratchov a...@caoua.org wrote:

 On Thu, May 08, 2014 at 12:35:56PM -0400, Ted Unangst wrote:
 This is wrong in several ways.
 
 Never cast sizeof down, always cast the comparison variable up.
 
 I'll specifically call out this change:
 
 -if (snprintf(buf, sizeof(buf)) = (int)sizeof(buf))
 +if ((size_t)snprintf(buf, sizeof(buf)) = sizeof(buf))
 
 
 note that the = operator promotes int to size_t, which makes the
 cast useless and could permit lines to be shortened.

Wouldn't that produce a signed vs. unsigned comparison?

Re: (int)sizeof in smtpd

[Ted Unangst]

On Thu, May 08, 2014 at 18:43, Alexandre Ratchov wrote:
 On Thu, May 08, 2014 at 12:35:56PM -0400, Ted Unangst wrote:
 This is wrong in several ways.
 
 Never cast sizeof down, always cast the comparison variable up.
 
 I'll specifically call out this change:
 
 -if (snprintf(buf, sizeof(buf)) = (int)sizeof(buf))
 +if ((size_t)snprintf(buf, sizeof(buf)) = sizeof(buf))
 
 
 note that the = operator promotes int to size_t, which makes the
 cast useless and could permit lines to be shortened.

Yes, I did that first, but somebody added -Wsign-compare to the
Makefile. Silencing that warning is the root of a lot of evil. The
cure is usually worse than the disease.