SEI CERT C Coding Standard

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changes.mady.by.user Aaron Ballman

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changes.mady.by.user Carol J. Lallier

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An example of a domain error is the square root of a negative number, such as sqrt(-1.0), which has no meaning in real arithmetic. On the other hand, 10 raised to the 1-millionth power, pow(10., 1e6), likely cannot be represented in an implementation's floating-point representation and consequently constitutes a range error. In both cases, the function will return some value, but the value returned is not the correct result of the computation.

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Code Block
if (/* Arguments that will cause a domain error. */) {
  /* Handle domain error. */
}
else {
  /* Perform computation. */
}

Range Checking

Range errors cannot usually be prevented, so the most reliable way to handle range errors is to detect when they have occurred and act accordingly.

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Code Block
#include <math.h>
#if defined(math_errhandling) \
  && (math_errhandling & MATH_ERREXCEPT)
#include <fenv.h>
#endif

/* ... */

#if defined(math_errhandling) \
  && (math_errhandling & MATH_ERREXCEPT)
  feclearexcept(FE_ALL_EXCEPT);
#endif
errno = 0;

/* Call the function. */

#if !defined(math_errhandling) \
  || (math_errhandling & MATH_ERRNO)
if (errno != 0) {
  /* Handle range error. */
}
#endif
#if defined(math_errhandling) \
  && (math_errhandling & MATH_ERREXCEPT)
if (fetestexcept(FE_INVALID
               | FE_DIVBYZERO
               | FE_OVERFLOW
               | FE_UNDERFLOW) != 0) {
  /* Handle range error. */
}
#endif

See FLP03-C. Detect and handle floating-point errors for more details on how to detect floating-point errors.

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Code Block
bgColor#ccccff
langc
#include <math.h>
 
void func(double x) {
  double result;

  if (isless(x, 0)) {
    /* Handle domain error. */
  }

  result = sqrt(x);
}

Anchor
HyperTrig
HyperTrig

...

Code Block
bgColor#ccccff
langc
#include <errno.h>
#include <math.h>

#if defined(math_errhandling) \
  && (math_errhandling & MATH_ERREXCEPT)
#include <fenv.h>
#endif
void func(double x) { 
  double result;
  result = sinh(x);
 
  #if defined(math_errhandling) \
    && (math_errhandling & MATH_ERREXCEPT)
    feclearexcept(FE_ALL_EXCEPT);
  #endif
  errno = 0;
 
  #if !defined(math_errhandling) \
    || (math_errhandling & MATH_ERRNO)
  if (errno != 0) {
    /* Handle range error. */
  }
  #endif
  #if defined(math_errhandling) \
    && (math_errhandling & MATH_ERREXCEPT)
  if (fetestexcept(FE_INVALID
                 | FE_DIVBYZERO
                 | FE_OVERFLOW
                 | FE_UNDERFLOW) != 0) {
    /* Handle range error. */
  }
  #endif
}

Anchor
Power
Power

...

Code Block
bgColor#ccccff
langc
#include <errno.h>
#include <math.h>
#if defined(math_errhandling) \
  && (math_errhandling & MATH_ERREXCEPT)
#include <fenv.h>
#endif

void func(double x, double y) {
  #if defined(math_errhandling) \
    && (math_errhandling & MATH_ERREXCEPT)
    feclearexcept(FE_ALL_EXCEPT);
  #endif
  errno = 0;

  double result;

  if (((x == 0.f) && islessequal(y, 0)) || (isless(x, 0))) {
    /* Handle domain error. */
  }

  result = pow(x, y);

  #if !defined(math_errhandling) \
    || (math_errhandling & MATH_ERRNO)
  if (errno != 0) {
    /* Handle range error. */
  }
  #endif
  #if defined(math_errhandling) \
    && (math_errhandling & MATH_ERREXCEPT)
  if (fetestexcept(FE_INVALID
                 | FE_DIVBYZERO
                 | FE_OVERFLOW
                 | FE_UNDERFLOW) != 0) {
    /* Handle range error. */
  }
  #endif
}

Risk Assessment

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Rule

Severity

Likelihood

Remediation Cost

Priority

Level

FLP32-C

mediumMedium

probableProbable

mediumMedium

P8

L2

Automated Detection

Tool

Version

Checker

Description

Fortify SCA

5.0

 

Can detect violations of this rule with CERT C Rule Pack

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