[cmake-developers] Alternate if() without implicit variable expansion

[Brad King]

On 09/05/2014 09:19 AM, Nils Gladitz wrote:
> On 09/05/2014 02:50 PM, Brad King wrote:
>> On 09/04/2014 11:58 AM, Nils Gladitz wrote:
>> - The dashboard submissions that bootstrap got many CMP0054
>>    warnings.  Most of them are the same warning repeated due
>>    to presence in a macro or loop.  Please update the warning
>>    to not warn on the same line more than once.  A set<> of
>>    already-emitted warning lines can be kept somewhere.
> 
> I'll look into it.

Good work on the revisions.

In the warning message:

  Quoted variables like 'SOME_VAR' are no longer dereferenced.

I think the 'single quoting' may be confusing since it looks
like an example of the quoting that is no longer dereferenced.
Instead use double-quotes:

  Quoted variables like "SOME_VAR" are no longer dereferenced.

I tested this on a few projects and found that the warning is
repeated in cases like:

 macro(foo VAR)
   if("${VAR}" MATCHES "^${VAR}$")
 endmacro()

because each call has a different quoted variable name after
macro expansion.  Since if() does not even get the arguments
until after the macro execution has substituted for ${VAR},
it is hard to eliminate this unless we take out the variable
name from the dedup set key.  I think perhaps we should do
that even though it could suppress cases with multiple separate
problems in a single if() command.  The goal of dedup is to
reduce the number of warnings that show up.  Once a developer
sits down to resolve the warnings, s/he will repeat running
CMake until all the warnings are gone anyway.

Thanks,
-Brad