Fix build for FreeBSD

[kkloberdanz]

CDRIVER-4465

• Some standard library features need __BSD_VISIBLE set to 1 to be enabled on FreeBSD
• Cmake does not properly detect res_search on FreeBSD. Since res_search has existed since 4.3 BSD (which is the predecessor of FreeBSD), it is safe to assume that this function will exist in libc on any version of FreeBSD.

[kkloberdanz]

You can use the following code to test that connecting via SRV works. One might want to connect to an instance on Atlas since the server does not support FreeBSD at this time.

#include <mongoc/mongoc.h>

int main (int argc, char **argv)
{
  mongoc_client_t *client = NULL;
  bson_error_t error = {0};
  mongoc_server_api_t *api = NULL;
  mongoc_database_t *database = NULL;
  bson_t *command = NULL, reply;

  // Initialize the MongoDB C Driver.
  mongoc_init ();

  client = mongoc_client_new("<INSERT_YOUR_CONNECTION_STRING_HERE>");

  // Set the version of the Stable API on the client.
  api = mongoc_server_api_new (MONGOC_SERVER_API_V1);
  if (!mongoc_client_set_server_api (client, api, &error))
  {
    // Error condition.
    printf("Error: %s\n", error.message);
    return 0;
  }

  // Get a handle on the "admin" database.
  database = mongoc_client_get_database (client, "admin");

  // Ping the database.
  command = BCON_NEW("ping", BCON_INT32(1));
  if (mongoc_database_command_simple(database, command, NULL, &reply, &error))
  {
    printf("Pinged your deployment. You successfully connected to MongoDB!\n");
  }
  else
  {
    // Error condition.
    printf("Error: %s\n", error.message);
    return 0;
  }


  // Perform Cleanup.
  bson_destroy (&reply);
  bson_destroy (command);
  mongoc_database_destroy (database);
  mongoc_client_destroy (client);
  mongoc_cleanup ();

  return 0;
}

Running:

$ uname
FreeBSD
$ cc test-srv.c -I ~/install/cdriver/include/libmongoc-1.0 -I ~/install/cdriver/include/libbson-1.0 -L ~/install/cdriver/lib/ -lbson-1.0 -lmongoc-1.0 && LD_LIBRARY_PATH=~/install/cdriver/lib ./a.out
Pinged your deployment. You successfully connected to MongoDB!

[kevinAlbs]

LGTM with one comment addressed.

[vector-of-bool]

LGTM