Thread: Difference in MSVC 6 & MS VC .Net

  1. #1
    Registered User
    Join Date
    Jan 2006

    Difference in MSVC 6 & MS VC .Net

    Hi friends,

    For the following piece code, there is no warning in MSVC 6 but MS VC++ .Net compiler issues the following warning:
    "warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data"

    Can someone please explain the reason for this warning.


    #include <stdio.h>
    #include <string.h>
    int main(void)
        int len;
        char s[] = "Hello World";
        len = strlen(s);
        printf("The length of the string \"%s\" is %d",s,len);
        return 0;

  2. #2
    Join Date
    Dec 2005
    I'm guessing here and could be completely wrong, but here goes:

    I believe size_t is typedef-ed as an unsigned integer (at least on my platform, Red Hat Linux). This makes sense because you're not going to have a negative size.

    strlen returns a size_t.

    If we assume the same on the Windows platform, the compiler is telling you that the statement

    len = strlen(s);

    is implicitly converting a size_t (unsigned int) into a signed int.

    If the value of strlen is large enough, it could overflow and len could actually end up as a negative number -- certainly not what is intended.

    Define len as a size_t and you should be all set.

    The difference in compiler warnings is probably due to the .Net compiler being newer (I think) and more strict (again, I think).

    Hope I haven't fouled this up too much!

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