[LLVMdev] [patch] EXPORTED_SYMBOL_FILE using mingw and cmake

[Dan Liew]

@ Brad : This might be a bug worth taking a look at

Hi Johannes,

Thanks for brining this to my attention.

> this is my first post to this list, so please excuse if submitting a patch
> without previous discussion is considered bad form or anything similar.

It's fine to submit a patch without discussion first if it's minor
change like this one, but usually they should normally go to the
llvm-commits mailing list instead of llvmdev. I'll try to review it
anyway.

> I
> encountered a bug in the CMake build while using MinGW (non-MSYS,
> non-CYGWIN) where the LTO_export fails with a “The syntax of the command is
> incorrect”  error. This error was previously fixed for Windows in general
> using TO_NATIVE_PATH, however CMake has a known bug (
> http://public.kitware.com/Bug/print_bug_page.php?bug_id=5939 ) where
> TO_NATIVE_PATH does not replace slashes by backslashes when the MinGW
> Makefiles generator is used. The attached patch provides a workaround.
> Considering that the bug has been open since 2007 it is unlikely that
> kitware will fix this anytime soon.

Yes considering the age of that bug report the workaround is probably
the best thing to do.

At a glance this patch looks okay but I would change it slightly so

- In the comments have a link to the bug you are working around
- Quote "${export_file}" so we can handle paths with spaces in (I
realise the old code didn't do that, but that is probably a mistake).

Also could you use MINGW in your conditional like this so you only
workaround the bug when necessary instead of all Windows platforms?

```
if(MINGW)
  # mingw workaround, as TO_NATIVE_PATH is implemented incorrectly
  # See http://public.kitware.com/Bug/print_bug_page.php?bug_id=5939
  string(REPLACE / \\ export_file_backslashes "${export_file}")
else()
  file(TO_NATIVE_PATH "${export_file}" export_file_backslashes)
endif()
```

I may have got this slightly wrong though as I'm not familiar with MinGW.

Thanks,
-- 
Dan Liew
PhD Student - Imperial College London