<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><br><div><div>On Mar 10, 2014, at 12:22 PM, Richard Trieu <<a href="mailto:rtrieu@google.com">rtrieu@google.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr">Marshall,<div><br></div><div>Equality comparisons appear to have their own subset of -Wunused-value in -Wunused-comparison. -Wunused-comparison checks both builtin and overloaded == and !=, which is the two warnings you saw. For the relational operators, -Wunused-value does not check for overloaded operators. So a < comparison of int's would trigger -Wunused-value warnings while a < comparison of iterators would not. This looks like an oversight from when the warning was implemented. I think the fix is to move the relational comparisons into -Wunused-comparison so that relational overloads will also be warned on.</div></div></blockquote><div><br></div>Sounds good to me.</div><div>If you don’t want to do this, I will … in about a week.</div><div><br></div><div>— Marshall</div><div><br><blockquote type="cite"><div dir="ltr">
<div><br></div><div>Richard.</div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Mar 10, 2014 at 11:23 AM, Chandler Carruth <span dir="ltr"><<a href="mailto:chandlerc@google.com" target="_blank">chandlerc@google.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">(CC-ing our local warnings expert...)</div><div class="HOEnZb"><div class="h5"><div class="gmail_extra">
<br><br><div class="gmail_quote">On Mon, Mar 10, 2014 at 11:13 AM, Marshall Clow <span dir="ltr"><<a href="mailto:mclow.lists@gmail.com" target="_blank">mclow.lists@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">As I was working on a libc++ issue (<br>
2263. Comparing iterators and allocator pointers with different const-character), if anyone cares, I wrote the following test program:<br>
<br>
#include <string><br>
<br>
int main() {<br>
std::string::iterator it;<br>
std::string::const_iterator cit;<br>
<br>
it == cit;<br>
it != cit;<br>
it < cit;<br>
it <= cit;<br>
it > cit;<br>
it >= cit;<br>
}<br>
<br>
I wanted to make sure that these were all legal comparisons using libc++ (and they are).<br>
I kind of expected some compiler warnings about “unused results” or something.<br>
<br>
What I didn’t expect was to get _two_ warnings. I figured either zero or some multiple of six.<br>
<br>
Apparently clang doesn’t like it if you don’t use the result of == or !=, but is perfectly happy with ignoring the results of >, >=, <, <=.<br>
<br>
Why is that?<br>
<br>
— Marshall<br>
<br>
<br>
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</blockquote></div><br></div>
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