Error handling

 

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Strings library

Algorithms

Numerics

Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Symbol index

 

Error handling

Error codes

Error codes

errno

Assertions

assert

static_assert (C11)(removed in C23)

Bounds checking

set_constraint_handler_s (C11)

abort_handler_s (C11)

ignore_handler_s (C11)

 

Error numbers

Defined in header <errno.h>
errno	macro which expands to POSIX-compatible thread-local error number variable (macro variable)
E2BIG, EACCES, ..., EXDEV	macros for standard POSIX-compatible error conditions (macro constant)

Assertions

Defined in header <assert.h>
assert	aborts the program if the user-specified condition is not true. May be disabled for release builds (function macro)
static_assert (C11)(removed in C23)	issues a compile-time diagnostic if the value of a constant expression is false (keyword macro)

Bounds checking The standard library provides bounds-checked versions of some existing functions (gets_s, fopen_s, printf_s, strcpy_s, wcscpy_s, mbstowcs_s, qsort_s, getenv_s, etc). This functionality is optional and is only available if __STDC_LIB_EXT1__ is defined. The following macros and functions support this functionality. Defined in header <errno.h> Defined in header <stdio.h> errno_t (C11) a typedef for the type int, used to self-document functions that return errno values (typedef) Defined in header <stddef.h> Defined in header <stdio.h> Defined in header <stdlib.h> Defined in header <string.h> Defined in header <time.h> Defined in header <wchar.h> rsize_t (C11) a typedef for the same type as size_t, used to self-document functions that range-check their parameters at runtime (typedef) Defined in header <stdint.h> RSIZE_MAX (C11) largest acceptable size for bounds-checked functions, expands to either constant or variable which may change at runtime (e.g. as the currently allocated memory size changes) (macro variable) Defined in header <stdlib.h> set_constraint_handler_s (C11) set the error callback for bounds-checked functions (function) abort_handler_s (C11) abort callback for the bounds-checked functions (function) ignore_handler_s (C11) ignore callback for the bounds-checked functions (function) Note: implementations of bounds-checked functions are available as open-source libraries Safe C and Slibc, and as part of Watcom C. There is also an incompatible set of bounds-checked functions available in Visual Studio.

(since C11)

Notes

Since C23, static_assert is itself a keyword, which may also be a predefined macro, so <assert.h> no longer provides it.

References

• C11 standard (ISO/IEC 9899:2011):

• 7.2 Diagnostics <assert.h> (p: 186-187)

• 7.5 Errors <errno.h> (p: 205)

• 7.19 Common definitions <stddef.h> (p: 288)

• 7.20 Integer types <stdint.h> (p: 289-295)

• 7.21 Input/output <stdio.h> (p: 296-339)

• 7.22 General utilities <stdlib.h> (p: 340-360)

• K.3.1.3 Use of errno (p: 584)

• K.3.2/2 errno_t (p: 585)

• K.3.3/2 rsize_t (p: 585)

• K.3.4/2 RSIZE_MAX (p: 585)

• 7.31.3 Errors <errno.h> (p: 455)

• 7.31.10 Integer types <stdint.h> (p: 456)

• 7.31.11 Input/output <stdio.h> (p: 456)

• 7.31.12 General utilities <stdlib.h> (p: 456)

• C99 standard (ISO/IEC 9899:1999):

• 7.2 Diagnostics <assert.h> (p: 169)

• 7.5 Errors <errno.h> (p: 186)

• 7.26.3 Errors <errno.h> (p: 401)

• 7.26.8 Integer types <stdint.h> (p: 401)

• 7.26.9 Input/output <stdio.h> (p: 402)

• 7.26.10 General utilities <stdlib.h> (p: 402)

• C89/C90 standard (ISO/IEC 9899:1990):

• 4.2 DIAGNOSTICS <assert.h>

• 4.1.3 Errors <errno.h>

• 4.13.1 Errors <errno.h>

• 4.13.6 Input/output <stdio.h>

• 4.13.7 General utilities <stdlib.h>

See also

math_errhandlingMATH_ERRNOMATH_ERREXCEPT (C99)(C99)(C99)

defines the error handling mechanism used by the common mathematical functions (macro constant)