Hi,
I would like to report one quite annoying issue related to Automake's `compile`
wrapper when it is used with `cl.exe` to compile some C++ files from Msys2.
I was building some GNU packages with MSVC's `cl.exe`, and compilation of some
C++ source files was failing with `cl.exe` reporting non-sensual filenames like
`H:E:/Msys2/{builddir}/somefile.cxx`.
Apparently, the issue is double conversion of a unix-style filename by Msys2's
shell. In example above, Msys2 is installed to `E:/Msys2` and builddir is
`/h/{builddir}`.
As I figured out later, it was happening because `compile` was converting
`/h/{builddir}/somefile.cxx` to `H:/{builddir}/somefile.cxx` and passing it as
`-TpH:/{builddir}/somefile.cxx` to `cl.exe`. However, Msys2 was interpreting
`/{builddir}/somefile.cxx` as a unix-style path and converted it again,
resulting in `-TpH:E:/Msys2/{builddir}/somefile.cxx`.
One way to work around this issue is :
```
export MSYS2_ARG_CONV_EXCL='-Tp'
```
However, this must be set by the user, which is inconvenient. I wonder if
anything can be done in the `compile` wrapper to fix this.
I am using latest versions of MSVC tools and `cl.exe` allows to pass argument
to `-Tp` as a separate argument and this seems to work correctly. However, I
don't know whether older versions of `cl.exe` allow it.
- Kirill Makurin
