Re: [Qemu-devel] [Qemu-block] [PATCH 0/2] Dynamic module loading for block drivers

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Wed, Jun 15, 2016 at 02:40:53PM -0400, Colin Lord wrote:
> 1) Denis Lunev suggested having block_module_load_one return the
> loaded driver to reduce duplicated for loops in many of the functions
> in block.c. I'd be happy to do this but wasn't completely sure how
> error handling would happen in that case since currently the return
> value is an integer error code. Would I switch to using the
> error handling mechanisms provided in util/error.c?

Yes, change "int foo(...)" to "MyObject *foo(..., Error **errp)".  The
Error object allows functions to provide detailed, human-readable error
messages so it can be a win.

If this change would cause a lot of changes you can stop the refactoring
from snowballing using error_setg_errno() to bridge new Error functions
with old int -errno functions:

  MyObject *foo(..., Error **errp)
  {
      /* I don't want propagate Error to all called functions yet, it
       * would snowball.  So just wrap up the errno:
       */
      ret = legacy_function(...);
      if (ret < 0) {
          error_setg_errno(errp, -ret, "legacy_function failed");
	  return NULL;
      }
  }

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