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11.10 Usage of math.h functions (frexp, ldex, scalbn and remquo) in C++ language (including EC++)

When certain arguments of the frexp, ldexp, scalbn, and remquo functions in math.h are of the int type, compiling the C++ or EC++ program generates object code that will enter an endless loop.

Conditions:

This problem occurs when both (1) and (2) are satisfied.

(1)	The program is in C++ or the -lang=cpp option is effective.

(2)	math.h is included and any of the following functions is called.

(a)	frexp(double, long) with 'int ' type second argument (except when the first argument is float-type and the -dbl_size=8 option is effective).

(b)	lldexp(double, long) with int type second argument (except when the first argument is float-type and the -dbl_size=8 option is effective).

(c)	scalbn(double, long) with int type second argument (except when the first argument is float-type and the -dbl_size=8 option is effective).

(d)	remquo(double, double, long) with 'int ' type third argument (except when the both the first and second arguments are float-type and the -dbl_size=8 option is effective).

Examples:

file.cpp:

  // Example of compiling C++ source that generates an endless loop

  #include <math.h>

  double d1,d2;

  int i;

  void func(void)

    d2 = frexp(d1, &i);

Command Line:

  ccrx -cpu=rx600 -output=src file.cpp

file.src: Example of the generated assembly program

  _func:

    ; ...(Omitted)

      ; Calling substitute function of frexp

    BSR __$frexp__tm__2_f__FZ1ZPi_Q2_21_Real_type__tm__4_Z1Z5_Type

    ; ...(Omitted)

  __$frexp__tm__2_f__FZ1ZPi_Q2_21_Real_type__tm__4_Z1Z5_Type:

  L11:

    BRA L11 ; Calls itself ==> endless loop

Countermeasures:

Select one of the following ways to avoid the problem.

(1)	Compile the program with the -lang=c or -lang=c99 option.

(2)	Change int and int * into long and long *.

(3)	Append the following declarations to each function that is being used.

      /* For the frexp function */

      static inline double frexp(double x, int *y)

      { long v = *y; double d = frexp(x,&v); *y = v; return (d); }

      /* For the ldexp function */

      static inline double ldexp(double x, int y)

      { long v = y; double d = ldexp(x,v); return (d); }

      /* For the scalbn function */

      static inline double scalbn(double x, int y)

      { long v = y; double d = scalbn(x,v); return (d); }

      /* For the remquo function */

      static inline double remquo(double x, double y, int *z)

      { long v = *z; double d = remquo(x,y,&v); *z = v; return (d); }

Example of (2):

Change in file.cpp:

  #include <math.h>

  double d1,d2;

  int i;

  void func(void)

    long x = i; /* Accept as long type temporary */

    d2 = frexp(d1, &x); /* Call with long type argument */

    i = x; /* Set the result for variable 'i' */

Example of (3):

Change in file.cpp:

  #include <math.h>

  /* Append declaration */

  static inline double frexp(double x, int *y)

  { long v = *y; double d = frexp(x,&v); *y = v; return (d); }

  double d1,d2;

  int i;

  void func(void)

    d2 = frexp(d1, &i);