How to write a small logger using varargs for WinCE

Question

I am trying to do some investigation on some external hardware which doesn't have logging.
For this I am making my own small logger using varargs in C. This is my code:

void write(const char* msg, ...)
{
    va_list args;
    va_start(args, msg);

    FILE* file = fopen("/network/cewin/loggerfile.txt", "a");
    if(file != NULL)
    {
        vfprintf(file, msg, args);
        fputc('\n', file);
        fclose(file);
        va_end(args);
    }
}

First I test this code on Windows 7, without issue, but on WinCE the lines containing arguments are not printed.

Here is an example:

write("Hello World") - Works on Win 7 and WinCE
write("Hello %s", "World") - Works on Win7, not on WinCE
write("Hello %i", 5) - Works on Win7, not on WinCE

I am trying to understand why the last 2 lines are working on Win7 but not on WinCE. Maybe I need to use something else than vfprintf ?

I cannot check the return values from methods, because of HW.

Answer 1

Not an answer -> I can't put code in comments - 'static' debug function, does not use varargs or vnprintf

void debugI(char *str, int iValue) 
{
    FILE *debugPtr = fopen ("/debugpath/debugFile.txt", "a");
    fprintf (debugPtr, "debugI %s:%d\n", str, iValue);
    fclose (debugPtr);
}