[clangd-dev] Automatically adding includes always inserts the full path on windows

Stefan Lietzau via clangd-dev clangd-dev at lists.llvm.org
Tue Jun 4 05:15:14 PDT 2019

Hey Ilya,
I was using commit ed4dbe63260f5a0a3410995b85b32f0ec34b0076 from the github llvm-mirror, dated 14 May 2019.
During my debugging I noticed that this function (https://github.com/llvm-mirror/clang/blob/b84e04d4c031c8ff9a1a6875381f4a34b923cad7/lib/Lex/HeaderSearch.cpp#L1677 ) tried to compare paths similar to these:
C:\foo/bar/baz with C:/foo/bar/baz. As these are compared as strings, they don’t match. I traced the problem back until I found that the compilation database entry contains only forward slashes while the suggested header contained backslashes. I’m not sure what the policy for path handling is for clang tooling and clangd in general. Without such information it’s difficult to fix this bug the right way.
@Kadir Çetinkaya, to me it looks like your change should solve the issue, I’ll test it and report my findings later. Comparing the date from the commit I used to build locally with the date of your change, suggests to me that my build should have included your fix.
Kind regards,
Stefan Lietzau
Von: Ilya Biryukov [mailto:ibiryukov at google.com] 
Gesendet: Dienstag, 4. Juni 2019 09:29
An: Stefan Lietzau; Kadir Çetinkaya
Cc: via clangd-dev
Betreff: Re: [clangd-dev] Automatically adding includes always inserts the full path on windows
Hi Stefan,
Thanks for reporting this. I don't think any of the active clangd developers run on Windows, so bugs like this can easily go unnoticed.
To add to what Kadir was requesting, could you point to a particular point in code that does the string comparison? If some of the strings come from user input (e.g. flags to the compiler), we should definitely normalize them before comparisons. 
@Kadir Çetinkaya, does your change also cover non-diagnostic use-cases? The function name looks very diagnostic-specific
On Mon, Jun 3, 2019 at 8:20 PM Stefan Lietzau via clangd-dev <clangd-dev at lists.llvm.org> wrote:
Hi there,
I’m using clangd with vscode on windows with the option to add includes when autocompleting symbols. However the inserted include is always absolute, even if the file is present in the include path (compile-commands.json generated by CMake). I tracked the problem down to a path comparison where one path coming from the compilation database contains forward slashes and the other path (header where the symbol definition was found) contains backslashes. Since this is a simple string comparison it fails and determines the header is not part of the include directories.
I don’t think the best fix would be to convert the paths before comparison or use a better comparison. Instead I think this is something that needs to be fixed deep inside clang tooling. That means I think the paths returned by the compilation database should be in a predictable format.
What do you guys think?
Kind regards
clangd-dev mailing list
clangd-dev at lists.llvm.org

Ilya Biryukov
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