The following code demonstrates a subtle bug in the Cygwin version of strtod(). The value it generates is slightly different than the value when using the math header files. This used to work correctly some time ago (months). I just took the time to track the problem down in our regression suite.
#include<math.h>
#include<stdio.h>
#include<stdlib.h>
int main()
{
double value = M_LN10;
printf("generate const. - value: %0.15f.\n", value);
printf("expected const. - value: 2.302585092994046.\n");
printf("\n");
value = strtod("2.30258509299404568402", 0);
/* Note: the last digit is incorrect. */
printf("generate strtod - value: %0.15f.\n", value);
printf("expected strtod - value: 2.302585092994046.\n");
return 0;
}