This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       The  erfc() function is provided because of the extreme loss of relative accuracy if erf(x) is called for
       large x and the result subtracted from 1.0.

       On error, the expressions (math_errhandling & MATH_ERRNO) and  (math_errhandling  &  MATH_ERREXCEPT)  are
       independent of each other, but at least one of them must be non-zero.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                          ERFC(3POSIX)

       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2017 defers to the ISO C standard.

       These functions shall compute the complementary error function 1.0 - erf(x).

       An   application   wishing   to   check   for  error  situations  should  set  errno  to  zero  and  call
       feclearexcept(FE_ALL_EXCEPT) before  calling  these  functions.  On  return,  if  errno  is  non-zero  or
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

       These functions may fail if:

       Range Error The result underflows.

                   If  the  integer  expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
                   set to [ERANGE].  If the integer expression (math_errhandling & MATH_ERREXCEPT) is  non-zero,
                   then the underflow floating-point exception shall be raised.

       Thefollowingsectionsareinformative.

       None.

       None.

       erfc, erfcf, erfcl — complementary error functions

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       Upon successful completion, these functions shall return the value of the complementary error function.

       If  the  correct  value  would  cause  underflow,  and is not representable, a range error may occur, and
       erfc(), erfcf(), and erfcl() shall return 0.0,  or  (if  the  IEC  60559  Floating-Point  option  is  not
       supported)  an  implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN,
       respectively.

       If x is NaN, a NaN shall be returned.

       If x is ±0, +1 shall be returned.

       If x is -Inf, +2 shall be returned.

       If x is +Inf, +0 shall be returned.

       If the correct value would cause underflow and is representable, a range error may occur and the  correct
       value shall be returned.

erf(), feclearexcept(), fetestexcept(), isnan()

       The Base Definitions volume of POSIX.1‐2017, Section4.20, TreatmentofErrorConditionsforMathematicalFunctions, <math.h>

       #include <math.h>

       double erfc(double x);
       float erfcf(float x);
       long double erfcl(long double x);