Rust lacunae

Posted Jun 24, 2021 15:24 UTC (Thu) by nye (subscriber, #51576)
In reply to: Rust lacunae by khim
Parent article: Rewriting the GNU Coreutils in Rust

> size > -1 is always false if size is unsigned with no warnings

$ clang++ -Weverything /tmp/test.cpp
/tmp/test.cpp:4:14: warning: result of comparison 'unsigned int' > 4294967295 is always false [-Wtautological-type-limit-compare]
    if (size > -1) {
        ~~~~ ^ ~~
/tmp/test.cpp:4:16: warning: implicit conversion changes signedness: 'int' to 'unsigned int' [-Wsign-conversion]
    if (size > -1) {
             ~ ^~

Even if you don't like using -Weverything because you don't want to opt in to newly added warnings, I do think that -Wsign-conversion is something that should always be turned on for code under active development. If you have substantial legacy codebase then you will doubtless need to add a lot of explicit casts to silence false positives, but, well, that's what you asked for.