# <assert.h>: Diagnostics

 #include <assert.h>


This header file defines a debugging aid.

As there is no standard error output stream available for many applications using this library, the generation of a printable error message is not enabled by default. These messages will only be generated if the application defines the macro

 __ASSERT_USE_STDERR


before including the <assert.h> header file. By default, only abort() will be called to halt the application.