#define axl_return_val_if_fail ( expr,
val   )     if (!(expr)) { __axl_log ("", AXL_LEVEL_CRITICAL, "Expresion '%s' have failed, returning: %s at %s (%s:%d)", #expr, #val, __AXL_PRETTY_FUNCTION__, __AXL_FILE__, __AXL_LINE__); return val;}

Allows to check a condition and return the given value if it is not meet.

Parameters:
expr The expresion to check.
val The value to return if the expression is not meet.