Nginx modules & C includes

[Valentin V. Bartenev]

On Sunday 01 September 2013 00:35:20 Jure Menart wrote:
> Dear all,
> 
> I'm new to the Nginx project and I am just getting familiar with it. Let me
> first thank to the contributors for the work they've put into to make the
> project so nice.
> 
> I've observed very 'strange' behaviour and took me quite a lot time to find
> the cause for it (not to understand it yet). Let me start in the beginning:
> - I've been playing with Hello world examples of course and then started to
> build bigger 'real' module.
> - Suddenly I've got very unpredictable behaviour and seg. faults.
> - I've stripped down my module back to real bare minimum - at the end I
> just included one command which sends "Hello world" string back to the
> client. The thing was still acting very strange: ngx_http_request_t seems
> 'unstable' - r->method with strange numbers, if I wanted to log in
> r->connection->log I've got seg. fault, ... I'm fairly sure my test module
> does not hot have any memory leaks because I am using only one static
> string which is put to the output buffer.
> - In the end I've removed the system C includes (sys/types.h, sys/stat.h,
> unistd.h) and my simple example started to work again - I've tried few
> times to add includes, put them before Nginx includes or after - it was
> very repeatable and the module was stable if I either did not include or
> include them after Nginx module:
> For example:
> <-- snip -->
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <unistd.h>
> 
> #include <ngx_config.h>
> #include <ngx_core.h>
> #include <ngx_http.h>
> <-- snip -->
> 
> Crashes my module, while:
> <-- snip -->
> #include <ngx_config.h>
> #include <ngx_core.h>
> #include <ngx_http.h>
> 
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <unistd.h>
> <-- snip -->
> 
> Seems to work.
> 
> My question: Did anybody observed this behaviour? Obviously the system
> includes can influence/change the includes in the Nginx. If this is known,
> are there any special limitations while including system headers?
> For sure this kind of behaviour is not nice and maybe it can be counted as
> bug (or at least be documented).
> 

There is a commentary in the C++ example module (the only example that we have):
http://trac.nginx.org/nginx/browser/nginx/src/misc/ngx_cpp_test_module.cpp#L19
  
 // nginx header files should go before other, because they define 64-bit off_t

  wbr, Valentin V. Bartenev