Question

I have a stupid bug in one of my c++ source for a project. I do in this part of the source I/O operations. I have a stupid bug where I print the fscanf read value. Below in this part :
Firstly, I don’t read the good value and when I print a float value, I get a decimal value with a comma ‘,’ instead of a point ‘.’ between the integer part and the floating part.

FILE* file3;
file3=fopen("test.dat","r");
float test1;
fscanf(file3," %f ",&test1);
printf("here %f\n",test1);
float test3 = 1.2345;
printf("here %f\n",test3);
fclose(file3);        

where test.dat file contains “1.1234” and I get at the execution :

here 1,000000
here 1,234500

So, I did a simple test C program compiled with g++ :

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

int main()
{
  FILE* file3;
  float test3;
  file3=fopen("test.dat","r");
  fscanf(file3,"%f",&test3);
  printf("here %f\n",test3);
  fclose(file3);
}

and it gives :

here 1.123400

This is the first time I have a bug like this. Anyone could see what’s wrong ?

Answer 1

Is your C++ locale somehow set to use a European convention? They use commas where we use points and points for thousand’s separators.

Have a look at settings of environment variables

LANG
LC_CTYPE
LC_ALL

try setting en_GB or en_US. Having established that it is a locale problem, next decide what behaviour makes sense. Is diplaying 1224,45 a bug at all? The user has locale set for a reason.