[cfe-dev] case-insensitive #include warning

Eric Niebler via cfe-dev cfe-dev at lists.llvm.org
Thu Apr 7 14:54:57 PDT 2016

I can say that this almost certainly does not work for non-ascii since it just uses StringRef::equals_lower. Is there any proper locale-sensitive string comparison routines in llvm that I can use?


On 4/7/16, 11:49 AM, "John Sully" <john at csquare.ca<mailto:john at csquare.ca>> wrote:

Out of curiosity have you tried this with some of the more interesting upper/lower case pairs like the turkish 'İ'?

It sounds like the way you're achieving this should allow this to work, but its worthwhile to try it.

On Thu, Apr 7, 2016 at 11:37 AM, Chris Lattner via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:

On Apr 5, 2016, at 4:03 PM, Eric Niebler via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:

Hi all,

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?

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.)

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.

Hi Eric,

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.

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>


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