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Error handling - cppreference.com

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Error numbers

Assertions

aborts the program if the user-specified condition is not true. May be disabled for release builds
(function macro) [edit]
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, fopen, printf, strcpy, wcscpy, mbstowcs, qsort, getenv, 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 the error callback for bounds-checked functions
(function) [edit]
abort callback for the bounds-checked functions
(function) [edit]
ignore callback for the bounds-checked functions
(function) [edit]

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

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>

See also