[CMake] Explanation....

[Matthew Woehlke]

On 2014-04-16 06:03, Rolf Eike Beer wrote:
> Am 16.04.2014 11:39, schrieb Johannes Zarl:
>> Instead of ``"${var}" STREQUAL "VALUE"'', write:
>>
>> IF ( var MATCHES "^VALUE$" )
>
> NOOOOO, please don't! I try hard to kill all those as it requires
> compiling a regular expression for a simple string match. Just change it
> to something that is no valid variable name, i.e. will never get expanded:
>
> if (" ${arg}" STREQUAL " TOTO")

set(" TOTO" "evil")

Admittedly it's much less likely that variable names containing 
non-identifier characters¹ will occur "by accident", the only truly safe 
way to avoid unintended implicit expansion is to either rely on implicit 
expansion (i.e. always assign your operands to variables and give the 
variable names as the literal arguments), or use some other command that 
doesn't perform expansion.

(¹ except for '-', which will often occur in automatically created 
variable names when used in project names, e.g. my-project_SOURCE_DIR.)

See also 
http://permalink.gmane.org/gmane.comp.programming.tools.cmake.devel/9936.

-- 
Matthew