[tz] suggestions for potential code improvements?

Paul Eggert eggert at cs.ucla.edu
Fri Jul 24 00:09:09 UTC 2015

On 07/23/2015 07:50 AM, Kees Dekker wrote:
> 1.Why do you not always initialize the variables that are now passed 
> to the INITIALIZE macro (see date.c/localtime.c/zic.c/private.h)? It 
> has (almost) no impact on performance and prevents strict compilers to 
> complain about (potentially) non-initialized variables.

Thanks for the careful reading of the code.  Although INITIALIZE does 
improve performance very slightly, it is not primarily about 
performance.  Mainly, it documents initialization that exists only to 
pacify compilers like GCC that would otherwise complain.  If the code 
always initialized variables even when not needed, the code would become 
more confusing to human readers, as we'd have to puzzle out why the 
initialization is present even though it is not used.

If this is a problem in your environment, you can compile with -Dlint.  
I often build this way:


as this provides -Dlint automatically.

> I don’t know whether all sprintf() implementations for all operating 
> systems respect the width/size specifier and allow non-0 terminated 
> string.

All sprintf implementations work that way.  This has been required by 
the C standard since C89 and is true for all C libraries in widespread 
use today.

I tried rewriting asctime.c along the lines that you suggested (see the 
attached patch).  On my platform (Fedora 21 x86-64, GCC 5.1.0) this made 
the zdump executable a tiny bit larger (7 bytes, for a new total of 
33077 bytes).  The wday_name and mon_name arrays are not likely to used 
elsewhere accidentally, as they're private to asctime_r and do not 
escape.  Although it's not a big deal either way, it should be OK to 
leave this code alone.
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