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  • Re: signed vs unsigned and gcc -Wsign-conversion

    From Tim Rentsch@tr.17687@z991.linuxsc.com to comp.lang.c on Mon Dec 15 00:25:01 2025
    From Newsgroup: comp.lang.c

    pozz <pozzugno@gmail.com> writes:

    After many years programming in C language, I'm always unsure if it is
    safer to use signed int or unsigned int.

    Of course there are situations where signed or unsigned is clearly
    better. For example, if the values could assume negative values,
    signed int is the only solution. If you are manipulating single bits
    (&, |, ^, <<, >>), unsigned ints are your friends.

    What about other situations? For example, what do you use for the "i"
    loop variable?

    I used unsigned types unless there is a compelling reason to use
    signed types. I used unsigned types for counts, array index values,
    sizes, lengths, extents, limits of the above, bits and masks. The
    most common reason for using signed types is for compatibility with
    some system interface (most commonly, signed int).

    There are cases where using an unsigned type rather than a signed
    type requires more thought and care. To me that need is a net
    positive rather than a negative.

    I recently activated gcc -Wsign-conversion option on a codebase and
    received a lot of warnings. I started to fix them, usually expliciting casting. Is it the way or is it better to avoid the warning from the beginning, choosing the right signed or unsigned type?

    My experience with such warnings is they generate too many false
    positives. I might turn on -Wsign-conversion every now and then
    as a sanity check, but not all the time. The "cure" of changing
    the code so the warnings go away is worse than the disease.
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