Error handling

From cppreference.com

Compiler support
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

[edit]

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)

[edit]

[edit]Error numbers

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

[edit]Assertions

Defined in header`<assert.h>`
assert	aborts the program if the user-specified condition is nottrue. May be disabled for release builds (function macro)[edit]
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 isoptional 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 typeint, used to self-document functions that returnerrno 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 assize_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)[edit]
abort_handler_s (C11)	abort callback for the bounds-checked functions (function)[edit]
ignore_handler_s (C11)	ignore callback for the bounds-checked functions (function)[edit]

Note: implementations of bounds-checked functions are available as open-source librariesSafe C andSlibc, and as part of Watcom C. There is also an incompatible set of bounds-checked functions available in Visual Studio.

(since C11)

[edit]Notes

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

[edit]References

Extended content
C23 standard (ISO/IEC 9899:2024): 7.2 Diagnostics <assert.h> (p: TBD) 7.5 Errors <errno.h> (p: TBD) 7.19 Common definitions <stddef.h> (p: TBD) 7.20 Integer types <stdint.h> (p: TBD) 7.21 Input/output <stdio.h> (p: TBD) 7.22 General utilities <stdlib.h> (p: TBD) K.3.1.3 Use of errno (p: TBD) K.3.2/2 errno_t (p: TBD) K.3.3/2 rsize_t (p: TBD) K.3.4/2 RSIZE_MAX (p: TBD) 7.31.3 Errors <errno.h> (p: TBD) 7.31.10 Integer types <stdint.h> (p: TBD) 7.31.11 Input/output <stdio.h> (p: TBD) 7.31.12 General utilities <stdlib.h> (p: TBD) C17 standard (ISO/IEC 9899:2018): 7.2 Diagnostics <assert.h> (p: TBD) 7.5 Errors <errno.h> (p: TBD) 7.19 Common definitions <stddef.h> (p: TBD) 7.20 Integer types <stdint.h> (p: TBD) 7.21 Input/output <stdio.h> (p: TBD) 7.22 General utilities <stdlib.h> (p: TBD) K.3.1.3 Use of errno (p: TBD) K.3.2/2 errno_t (p: TBD) K.3.3/2 rsize_t (p: TBD) K.3.4/2 RSIZE_MAX (p: TBD) 7.31.3 Errors <errno.h> (p: TBD) 7.31.10 Integer types <stdint.h> (p: TBD) 7.31.11 Input/output <stdio.h> (p: TBD) 7.31.12 General utilities <stdlib.h> (p: TBD) 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>

Extended content

C23 standard (ISO/IEC 9899:2024):

7.2 Diagnostics <assert.h> (p: TBD)

7.5 Errors <errno.h> (p: TBD)

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

7.20 Integer types <stdint.h> (p: TBD)

7.21 Input/output <stdio.h> (p: TBD)

7.22 General utilities <stdlib.h> (p: TBD)

K.3.1.3 Use of errno (p: TBD)

K.3.2/2 errno_t (p: TBD)

K.3.3/2 rsize_t (p: TBD)

K.3.4/2 RSIZE_MAX (p: TBD)

7.31.3 Errors <errno.h> (p: TBD)

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

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

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

C17 standard (ISO/IEC 9899:2018):

7.2 Diagnostics <assert.h> (p: TBD)

7.5 Errors <errno.h> (p: TBD)

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

7.20 Integer types <stdint.h> (p: TBD)

7.21 Input/output <stdio.h> (p: TBD)

7.22 General utilities <stdlib.h> (p: TBD)

K.3.1.3 Use of errno (p: TBD)

K.3.2/2 errno_t (p: TBD)

K.3.3/2 rsize_t (p: TBD)

K.3.4/2 RSIZE_MAX (p: TBD)

7.31.3 Errors <errno.h> (p: TBD)

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

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

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

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>

[edit]See also

math_errhandlingMATH_ERRNOMATH_ERREXCEPT (C99)(C99)(C99)	defines the error handling mechanism used by the common mathematical functions (macro constant)[edit]
C++ documentation forError handling