Re: [Lzip-bug] include pthread.h in plzip.cc

[Ersek, Laszlo]

On Tue, 19 Jan 2010, Antonio Diaz Diaz wrote:

> It seems the line:
>  #include <pthread.h>
> needs to be inserted at line 29 of plzip.cc.

That depends on personal taste. (Pertinently enough, a conversation 
concerning this taste is just running in the comp.lang.c Usenet newsgroup, 
see [0].)

a) One approach is to #include headers only in .c (or .cc) files, and 
forbid recursive inclusion, ie. #include preprocessing directives in 
headers. Each .c (.cc) file is responsible for collecting all necessary 
declarations (and in the right order) from the appropriate headers.

b) Another approach (which I profess mine) is to provide everything 
necessary (and nothing more) in a header so that the declarations 
providing the reason d'etre for the header can be immediately used. For 
example, if you #include <stdlib.h> for malloc(), you expect size_t 
(parameter type of malloc()) to become visible; you don't want to have to 
#include <stddef.h> too.

"main.h" declares struct Cond, and struct Cond has a member of type 
pthread_mutex_t. Approach "b" says: let's #include <pthread.h> in 
"main.h", so that whoever tries to define (allocate) a struct Cond object, 
he/she can do that without further #include's. "plzip.cc" depends on 
"main.h" and rightfully so, it defines (allocates) struct Cond objects. 
When looked at under approach "b", the #include is missing from "main.h" 
(it was there in llzip-0.03 :)).

According to approach "a", the #include directive should be added to 
"plzip.cc". "main.cc" (also dependent on "main.h") does include 
<pthread.h> before the inclusion of "main.h", hence it indeed reflects 
approach "a" (which is perfectly fine if used consistently, just not my 
taste (which doesn't matter, since Antonio is the maintainer (and more and 
more, principal author) of plzip)). I reckon he likes approach "a" (*) and 
converted the source to it, and missed this single inclusion.

(*) For example, "arg_parser.h" employs std::string but doesn't include 
<string> (or anything else). "arg_parser.cc" does.

Cheers,
lacos

[0] 
http://groups.google.com/group/comp.lang.c/browse_frm/thread/8ac1309e95a1004a/24ca4109ea30be04?tvc=1#24ca4109ea30be04