FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT
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C
Concurrency support (C11)
Floating-point environment
Functions
(C99)
(C99)
(C99)
(C99)(C99)
(C99)(C99)
(C99)
(C99)
(C99)
Macro constants
FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW
(C99)
(C99)
Defined in header
<fenv.h>
#define FE_DIVBYZERO /*implementation defined power of 2*/
(since C99)
#define FE_INEXACT /*implementation defined power of 2*/
(since C99)
#define FE_INVALID /*implementation defined power of 2*/
(since C99)
#define FE_OVERFLOW /*implementation defined power of 2*/
(since C99)
#define FE_UNDERFLOW /*implementation defined power of 2*/
(since C99)
#define FE_ALL_EXCEPT FE_DIVBYZERO | FE_INEXACT | \
(since C99)
FE_INVALID | FE_OVERFLOW | \
All these macro constants (except FE_ALL_EXCEPT) expand to integer constant expressions that are distinct powers of 2, which uniquely identify all supported floating-point exceptions. Each macro is only defined if it is supported.
The macro constant FE_ALL_EXCEPT, which expands to the bitwise OR of all other FE_*, is always defined and is zero if floating-point exceptions are not supported by the implementation.
Constant
Explanation
FE_DIVBYZERO
pole error occurred in an earlier floating-point operation
FE_INEXACT
inexact result: rounding was necessary to store the result of an earlier floating-point operation
FE_INVALID
domain error occurred in an earlier floating-point operation
FE_OVERFLOW
the result of an earlier floating-point operation was too large to be representable
FE_UNDERFLOW
the result of an earlier floating-point operation was subnormal with a loss of precision
FE_ALL_EXCEPT
bitwise OR of all supported floating-point exceptions
The implementation may define additional macro constants in <fenv.h> to identify additional floating-point exceptions. All such constants begin with FE_ followed by at least one uppercase letter.
See math_errhandling for further details.
[edit] Example
Run this code
#include <stdio.h> #include <math.h> #include <float.h> #include <fenv.h> #pragma STDC FENV_ACCESS ON void show_fe_exceptions(void) { printf ("exceptions raised:"); if(fetestexcept (FE_DIVBYZERO)) printf (" FE_DIVBYZERO"); if(fetestexcept (FE_INEXACT)) printf (" FE_INEXACT"); if(fetestexcept (FE_INVALID)) printf (" FE_INVALID"); if(fetestexcept (FE_OVERFLOW)) printf (" FE_OVERFLOW"); if(fetestexcept (FE_UNDERFLOW)) printf (" FE_UNDERFLOW"); feclearexcept (FE_ALL_EXCEPT); printf ("\n"); } int main(void) { printf ("MATH_ERREXCEPT is %s\n", math_errhandling & MATH_ERREXCEPT ? "set" : "not set"); printf ("0.0/0.0 = %f\n", 0.0/0.0); show_fe_exceptions(); printf ("1.0/0.0 = %f\n", 1.0/0.0); show_fe_exceptions(); printf ("1.0/10.0 = %f\n", 1.0/10.0); show_fe_exceptions(); printf ("sqrt(-1) = %f\n", sqrt (-1)); show_fe_exceptions(); printf ("DBL_MAX*2.0 = %f\n", DBL_MAX *2.0); show_fe_exceptions(); printf ("nextafter(DBL_MIN/pow(2.0,52),0.0) = %.1f\n", nextafter (DBL_MIN /pow (2.0,52),0.0)); show_fe_exceptions(); }
Possible output:
MATH_ERREXCEPT is set 0.0/0.0 = nan exceptions raised: FE_INVALID 1.0/0.0 = inf exceptions raised: FE_DIVBYZERO 1.0/10.0 = 0.100000 exceptions raised: FE_INEXACT sqrt(-1) = -nan exceptions raised: FE_INVALID DBL_MAX*2.0 = inf exceptions raised: FE_INEXACT FE_OVERFLOW nextafter(DBL_MIN/pow(2.0,52),0.0) = 0.0 exceptions raised: FE_INEXACT FE_UNDERFLOW
[edit] References
- C11 standard (ISO/IEC 9899:2011):
- 7.6/6 Floating-point environment <fenv.h> (p: 207)
- C99 standard (ISO/IEC 9899:1999):
- 7.6/5 Floating-point environment <fenv.h> (p: 188)
[edit] See also
(C99)(C99)(C99)
(macro constant) [edit]
C++ documentation for floating-point exception macros