[cmake-developers] Issues with generator expressions and lists

[Stephen Kelly]

Hi,

I've been working on the JOIN genex in my join-genex branch and encountered 
some generic issues along the way relating to use of lists with generator 
expressions. I don't propose merging the JOIN feature for the next release, 
but there seems to be remaining issues which would be best solved in 2.8.11.

I think at some point, we wanted to be able to use lists in the arguments of 
generator expressions, such as. I added cmGeneratorExpression::Split in 
f99196dc0cde6e5868cc74c603a78b10f1ba324a and used it in 
a3aedb8152ad6fcdb42fd04e45307eea6ce0043e so that targets in 

 $<1:foo_target;bar_target> 

could be extracted.

For the JOIN genex to be useful, I'll need to be able to handle lists there 
too. I'm hitting problems of conflicting requirements though, when used with 
add_custom_command, and I'm not certain what to about them. 

One solution to the class of problem I'm come up against as it relates 
specifically to the Qt 4 macros is to always write to the parameters file, 
not only on Windows. That at least hides the argument list from 
add_custom_command. That is not a generic solution though.

Any comments on this stuff?

Thanks,

Steve.