[LLVMdev] [cfe-dev] Unicode path handling on Windows

Ahmed Charles ahmedcharles at gmail.com
Fri Sep 30 10:53:25 PDT 2011

Note: /Za shouldn't be used.

P.S. I'd say more, but it'd only water down the message.
From: Nikola Smiljanic
Sent: 9/30/2011 12:45 AM
To: Bryce Cogswell
Cc: cfe-dev; llvmdev
Subject: Re: [LLVMdev] [cfe-dev] Unicode path handling on Windows

I tried to do the conversion to lowercase inside GetFullPath by adding an
additional bool parameter to this function. It's not perfect but seems much
better than repeating the whole UTF8 to UTF16 and UTF16 to UTF8 conversion
again. The problem I have is with access to CharLowerBuffW. I need Windows.h
for this function but when I try to include it I get a bunch of errors
because Language Extensions are disabled, /Za switch. Do I just enable them
and include Windows.h inside and #ifdef section?

On Thu, Sep 29, 2011 at 7:57 AM, Bryce Cogswell <bryceco at gmail.com> wrote:

> I agree they are broken on all platforms. However, FileManager.cpp already
> contains an #if WIN32 conditional around the code calling LowercaseString,
> so you can use MultiByteToWideChar and CharLowerBuffW directly there, and
> not call the LowercaseString function. I don't think there are any other
> places where LowercaseString is called with non-ascii data, so you can punt
> on fixing it for now.
> On Sep 28, 2011, at 10:11 PM, Nikola Smiljanic wrote:
> I have a problem with Lowercase and Uppercase functions. These are broken
> on all platforms, not only Window, so I can't just #ifdef and use CharLowerBuffW.
> I need a portable way to convert from UTF8 to UTF16. There is set of
> functions inside clang/Basic/ConvertUTF, but LLVM can't depend on this. What
> do I do?
> On Tue, Sep 27, 2011 at 5:09 AM, Bryce Cogswell <bryceco at yahoo.com> wrote:
>> I think the assert you have for _stat64i32 is fine. It is a constant
>> expression so should compile to nothing, and the chance of the definition
>> changing is pretty much zero.
>> LowercaseString appears to be used by ASM printers where the output is
>> expected to be ASCII, and then some WIN32-conditioned code in
>> FileManager.cpp. I hate to say it but you'll probably need to convert the
>> UTF-8 paths to wide char, lower case it using CharLowerBuffW (since it needs
>> to match the casing rules used by NTFS), and then convert back to UTF-8.
>> If you need to be pedantic about recognizing whether two paths are the
>> same on Windows you also need to call GetFullPathName in order to expand any
>> 8.3 path components, but this is an expensive function so I wouldn't do it
>> unless absolutely necessary.
>> There is also a call to _fullpath in there that needs to be changed to
>> _wfullpath.
>> The rest of the patch looks good.
>> On Sep 23, 2011, at 9:57 AM, Nikola Smiljanic wrote:
>> Here's a new patch that fixes all the issues mentioned before. Note that
>> this isn't final, I didn't want to replace all calls to ::stat so that it's
>> easier to review.
>> I have only one more questions:
>> 1. _wopen accepts _stat64i32 instead of stat structure. These two are
>> exactly the same, the only difference is that stat uses time_t
>> and _stat64i32 uses __time64_t (time_t is a typedef for __time64_t but this
>> depends on one more macro). I check to see that size of these two structures
>> is the same, but is there something more that I could do? I'd also like to
>> use some kind of static assert instead of runtime assert.
>> I've also noticed that function LowercaseString (the same applies to
>> UppercaseString) doesn't work with UTF8 input. It's calling isupper and
>> tolower and these functions can't handle UTF8. This should get a new issue
>> probably?
>> On Wed, Sep 21, 2011 at 1:41 AM, Aaron Ballman <aaron at aaronballman.com>wrote:
>>> On Tue, Sep 20, 2011 at 4:15 PM, Nikola Smiljanic <popizdeh at gmail.com>
>>> wrote:
>>> > OK since this approach makes sense I'll shoot with my questions :)
>>> > 1. Where should get_utf8_argv go and is the name of this function OK?
>>> Right
>>> > now the function is inside llvm::sys::fs namespace because I need
>>> access to
>>> > Windows.h, should I leave it there.
>>> I don't think it belongs there as it has nothing to do with the file
>>> system.  However, I'm not familiar enough to know of a better place
>>> for it either.  Hopefully someone else can chime in with an idea.
>>> > 2. get_utf8_argv allocates new char** representing utf8 argv, should I
>>> > deallocate this inside driver.cpp, use std::vector<std::string> instead
>>> or
>>> > ignore the allocation completely?
>>> Perhaps some SmallVectors would make sense here?  An inner one to hold
>>> the arg data, and an outer one to hold the list of inner vectors.
>>> Then you can do the cleanup within the call.
>>> > 3. There is an #ifdef inside driver.cpp right now that I don't like.
>>> > get_utf8_argv works for windows only, but I could change the function
>>> to
>>> > accept argv and return it as vector of utf8 strings. It would convert
>>> char*
>>> > to std::string on unix and use GetCommandLine + utf8 conversion on
>>> windows.
>>> I have no concrete opinion one way or the other on this.
>>> > 4. Should I wrap functions like ::fstat and ::close for consistency
>>> even
>>> > though they don't work with paths?
>>> I don't believe so.
>>> > I'll fix everything that is formatting related. You're right, current
>>> patch
>>> > has Open only for windows but I'll add the other one as well.
>>> Thanks for the help!
>>> ~Aaron
>> <clang.patch><llvm.patch>
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