6.4 <errno.h> Errors
The header file errno.h consists of macros that provide error codes that
are reported by certain library functions. The variable errno might be
assigned any value greater than zero by these library functions. Preprocessor macros are
defined to represent these values. Library functions will never set
errno to zero. At program start-up, errno is
zero.
To test if a library function encounters an error, the program should store the zero
value in errno immediately before calling the library function. The
value should be checked after the call, before subsequent code can change the value.
errno Macro/Variable
Contains the value of an error when an error occurs in several library functions.
Include
<errno.h>
Remarks
This is implemented as a macro that aliases the int object
__errno_val with all MPLAB XC implementations except for XC8
PIC, where it is defined as an int object in its own right.
The value of errno will be zero at program startup. It is set to a
non-zero integer value by certain library functions when an error occurs. The
errno object should be reset to zero prior to calling a
function that may set it.
EDOM Macro
Represents a domain error.
Include
<errno.h>
Remarks
EDOM represents a domain error, which occurs when an
input argument is outside the domain in which the function is defined.
EILSEQ Macro
Represents a wide character encoding error.
Include
<errno.h>
Remarks
EILSEQ represents a wide character encoding error, when
the character sequence presented to the underlying mbrtowc function
does not form a valid (generalized) multibyte character, or if the code value passed
to the underlying wcrtomb does not correspond to a valid
(generalized) overflow or underflow error, which occurs when a result is too large
or too small to be stored.
ERANGE Macro
Represents an overflow or underflow error.
Include
<errno.h>
Remarks
ERANGE represents an overflow or underflow error, which
occurs when a result is too large or too small to be stored.