Name

Per-Server Merger

Synopsis

void *module_merge_server(pool *pPool, void *base_conf, void *new_conf)

Once the Config files have been read, this function is called once for each virtual host, with base_conf pointing to the main server’s configuration (for this module) and new_conf pointing to the virtual host’s configuration. This gives you the opportunity to inherit any unset options in the virtual host from the main server or to merge the main server’s entries into the virtual server, if appropriate. It returns a pointer to the new configuration structure for the virtual host (or it just returns new_conf, if appropriate).

It is possible that future changes to Apache will allow merging of hosts other than the main one, so don’t rely on base_conf pointing to the main server. See Example 21-4 (1.3) for an excerpt from mod_cgi.c.

Example

Example 21-4. mod_cgi.c

static void *merge_cgi_config(pool *p, void *basev, void *overridesv)
{
    cgi_server_conf *base = (cgi_server_conf *) basev, *overrides = (cgi_server_conf *) 
overridesv;

    return overrides->logname ? overrides : base;
}

Although this example is exceedingly trivial, a per-server merger can, in principle, do anything a per-directory merger does — it’s just that in most cases it makes more sense to do things per-directory, so the interesting examples can be found there. This example does serve to illustrate a point of confusion — often the overriding configuration is called overrides (or some variant thereof), which to our ears implies the exact opposite precedence to that desired.

Again, the only change in 2.0 is that pool has become apr_pool_t.