nghttp3_set_debug_vprintf_callback
==================================

Synopsis
--------

*#include <nghttp3/nghttp3.h>*

.. function:: void nghttp3_set_debug_vprintf_callback( nghttp3_debug_vprintf_callback debug_vprintf_callback)

    
    `nghttp3_set_debug_vprintf_callback` sets a debug output callback
    called by the library when built with :macro:`DEBUGBUILD` macro
    defined.  If a callback function is not set by this function, debug
    log is written into standard error output.
    
    For builds without :macro:`DEBUGBUILD` macro defined, this function
    is noop.
    
    Note that building with :macro:`DEBUGBUILD` may cause significant
    performance penalty to libnghttp3 because of extra processing.  It
    should be used for debugging purpose only.
    
    .. Warning::
    
      Building with :macro:`DEBUGBUILD` may cause significant
      performance penalty to libnghttp3 because of extra processing.
      It should be used for debugging purpose only.  We write this two
      times because this is important.