NAN constant value error on compilation under ICC

[Sheridan-Methven__Ol]

I have the following code (called misc.c)

#include <stdlib.h>
#include <stdio.h>
#include <mkl.h>
#include <math.h>

// double my_value = 1.0f;  // Works fine. 
double my_value = NAN;  // Gives "error: expression must have a constant value".
int main ()
{
//    double my_value = NAN;  // Works fine.
    printf("my value is %f\n", my_value);
    return 0;
}

However, when I try to compile this using ICC (18.0.0 20170811) I get the following error: 

% icc -mkl -D__PURE_INTEL_C99_HEADERS__ misc.c  -o misc 
misc.c(6): error: expression must have a constant value
  double my_nan = NAN;

However, if I use GCC this works fine (after commenting out the mkl.h include line) and runs as expected. 

I find this a bit strange and unexpected. Should I have expected this?

[Vladimir_P_1234567890]

bash-4.2$ gcc --version
gcc (GCC) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

bash-4.2$ gcc misc.c  -o misc -Wall -Wextra -ansi -pedantic
misc.c:9:1: error: C++ style comments are not allowed in ISO C90
 // double my_value = 1.0f;  // Works fine.
 ^
misc.c:9:1: error: (this will be reported only once per input file)
misc.c:10:19: error: ‘NAN’ undeclared here (not in a function)
 double my_value = NAN;  // Gives "error: expression must have a constant value".
                   ^~~
bash-4.2$

It think If you want icc to be more flexible you need to remove -D__PURE_INTEL_C99_HEADERS__ limitation or comply with C99 standard

Vladimir