<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Apr 5, 2016, at 4:03 PM, Eric Niebler via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" class="">cfe-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div class="">Hi all,</div>
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<div class="">I have an initial cut at patch that issues a warning when a file is #included on a case-insensitive file system that would not be found on a case-sensitive system. Is there interest?</div>
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<div class="">Since this is a hard problem to solve perfectly, I have opted for a strategy that is efficient and conservative about issuing diagnostics. That is, it shouldn't give false positives, but it will fail to diagnose some non-portable paths. On *nix systems,
the low-level APIs that stat and open files get an extra call to ::realpath, and the result is cached along with the rest of the file metadata. On Windows, I use a combination of GetFullPathName and GetLongPathName to get the same effect. (I don't believe
that's guaranteed to get the physical name including case, but it seems to mostly work in my testing.)</div>
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<div class="">Due to how I compare path components, a relative path like "NoTtHeRiGhTcAsE/../correctly-cased.h" will not be diagnosed, but "../NoTtHeRiGhTcAsE/correctly-cased.h" will be. Catching more cases requires many more round trips to the disk, which I wanted
to avoid.</div>
</div></div></div></div></blockquote><br class=""></div><div>Hi Eric,</div><div><br class=""></div><div>This would be a hugely welcomed feature, but have you done any performance analysis of this? The preprocessor and the data structures you are touching are very sensitive.</div><div><br class=""></div><div>You can stress test the preprocessor by using the "clang -cc1 -Eonly” mode. If you’re on a mac, I’d recommend timing <Cocoa/Cocoa.h></div><div><br class=""></div><div>-Chris</div><div><br class=""></div><br class=""></body></html>