[CMake] Re: How to update a variable inside a subfolder?

[Alan W. Irwin]

On 2007-01-30 21:23+0100 Peter Soetens wrote:

> Quoting kitts <kitts.mailinglists at gmail.com>:
>> On Monday 29 Jan 2007 IST, Alan W. Irwin wrote:
>>> BTW, my understanding of why variables set in subdirectories do not
>>> propagate to parent directories is the CMake developers are using this
>>> rule to (rightly) limit variable scope to make it more difficult to have
>>> cross-directory bugs.
>
> What is a cross-directory bug ?

If you limit scope, then you can have variables of the same name in
different directories not interfering with each other.

>
> We are using ENV{MY_SOURCES_LIST} to do the trick. This bypasses the use of 
> CMake variables:
>
> in subdir:
> SET( ENV{MY_SOURCES_LIST} "$ENV{MY_SOURCES_LIST} Src1.cpp Src2.cpp")
>
> in main dir:
> SET(ENV{MY_SOURCES_LIST} "")
> ADD_SUBDIRECTORY( subdir )
> SET(FINAL_SOURCES $ENV{MY_SOURCES_LIST})
>
> Now my $100.000.000 question is: And how does this trigger the 
> cross-directory bug ?

Not "the" cross-directory bug.  However, environment variables introduce the
possibility of cross-directory bugs. Since such variables have global scope
in every directory you will have to be extra careful to give unique names to
them.

Please send a cheque for $100.000.000.  :-)

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the Yorick front-end to PLplot (yplot.sf.net); the
Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
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