ngx_conf_t args count

[Jeffrey Walton]

On Mon, Dec 16, 2013 at 2:15 AM, Ruslan Ermilov <ru at nginx.com> wrote:
> On Sun, Dec 15, 2013 at 04:31:08PM -0500, Jeffrey Walton wrote:
>> From Miller's http://www.evanmiller.org/nginx-modules-guide.html, section 5.2:
>>
>> ngx_http_upstream_hash(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
>>  {
>>     ngx_http_upstream_srv_conf_t  *uscf;
>>     ngx_http_script_compile_t      sc;
>>     ngx_str_t                     *value;
>>     ngx_array_t                   *vars_lengths, *vars_values;
>>
>>     value = cf->args->elts;
>>
>>     /* the following is necessary to evaluate the argument to "hash"
>> as a $variable */
>>     ngx_memzero(&sc, sizeof(ngx_http_script_compile_t));
>>
>>     vars_lengths = NULL;
>>     vars_values = NULL;
>>
>>     sc.cf = cf;
>>     sc.source = &value[1];
>>     ...
>> }
>>
>> How does one know that value[1] is valid? Shouldn't cf->args->nelts be
>> checked first? Or does ngx_conf_t always have at least two options?
>> Related: why was value[0] not chosen?
>
> value[0] is the directive name, "hash" in this case.  It's
> like argv[] in main().
>
> The "hash" directive can be specified in the "upstream" context
> (NGX_HTTP_UPS_CONF) and it takes exactly one argument (NGX_CONF_TAKE1).
> The generic configuration parser code ensures that the argument
> exists.
>
> http://www.evanmiller.org/nginx-modules-guide.html#directives
Ah, thanks. It makes perfect sense.

Jeff