[CMake] Found the cause - was: Re: Include path Tcl under Cygwin

[Arjen Markus]

On Thu, 4 Jul 2013 02:22:22 -0700 (PDT)
  "Alan W. Irwin" <irwin at beluga.phys.uvic.ca> wrote:

> 
> In a perfect world (assuming there is a well understood 
>set of
> standard locations for Cygwin system files, that CMake 
>knows about
> those when you are running on the Cygwin platform, _and_ 
>that CMake
> searches those locations before it searches the "raw" 
>Windows system
> locations) you would be correct. 
...
> And in my particular case (lots of packages that I want 
>to use that
> are often not installed in standard system locations) I 
>use
> CMAKE_INCLUDE_PATH, CMAKE_LIBRARY_PATH, and PATH 
>extensively to give
> CMake some guidance for where it finds software.
> 

Well, it took me some time o realise what was the 
difference
between my running CMake for the PLplot package and 
Marco's,
but when I tried it with a minimal build set-up:

set(PACKAGE testcygwin)
include(FindTCL)

I found that in this case it was finding the Tcl include
files in the directory /usr/include. So I thought there 
was
something odd going on in the PLplot set-up. Not quite
impossible, because PLplot takes care of many programming
languages, graphical options and libraries.

But then I realised that I use the option 
CMAKE_LEGACY_CYGWIN_WIN32=ON (in a shell script, as I am
too lazy to type the full command each time, but also to
ensure I can reproduce my build sessions).

The reason for using this option is that PLplot does use
the WIN32 variable for several Windows-specific aspects.
Some of them may not be important in the case of Cygwin
but others are (like building the wingcc device driver).

When I used that option on my minimal project, it indeed
found the Tcl include files in c:\tcl\include.

Since CMake under Cygwin is consistently finding the
Cygwin versions of all other Tcl-related things, I 
consider
this a bug related to this variable.

The bug is somewhere in the FIND_PATH command - the 
correct
path /usr/include is not contained in the hints that are
passed in the FindTCL module, so it digs that up all by
itself.

Regards,

Arjen

 

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