[SOLVED] CMake Generator Expressions and CONFIG variable query

Issue

This CMake Doc : https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html tells us that :

$<CONFIG> Configuration name.

and that :

Conditional generator expressions depend on a boolean condition that must be 0 or 1.

$<condition:true_string> Evaluates to true_string if condition is 1. Otherwise evaluates to the empty string.

$<IF:condition,true_string,false_string> New in version 3.8.

Evaluates to true_string if condition is 1. Otherwise evaluates to false_string.

Typically, the condition is a boolean generator expression. For instance,

$<$<CONFIG:Debug>:DEBUG_MODE> expands to DEBUG_MODE when the Debug configuration is used, and otherwise expands to the empty string.

If I understand correctly, in Visual Studio, if I'm switching from Debug to Release this line :

$<$<CONFIG:Debug>:DEBUG_MODE>

Should also expand to DEBUG_MODE, isn't it ? because CONFIG will contain, according to my understanding "Release" and it's a non empty string, thus it will expand to Debug, than this last will make the first generator expression expand to DEBUG_MODE because of this statement in the documentation :

$condition:true_string Evaluates to true_string if condition is 1. Otherwise evaluates to the empty string.

I know I'm wrong, please help me to understand how it works.

Solution

because CONFIG will contain

CONFIG does not contain, it's not a condition, it's a specific Variable query with special rules.

$<CONFIG:cfgs>

1 if config is any one of the entries in cfgs, else 0. [...]

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Let's say it works like this:

• extract the parts A and B like $<A:B>
• if part A is CONFIG - then do stuff related to CONFIG
• if part A is, for example, STREQUAL - then do stuff on B related to STREQUAL.
• for each case ...
• otherwise it's a condition, so if it's 1, then return B, otherwise empty string.

Answered By - KamilCuk

Answer Checked By - Clifford M. (WPSolving Volunteer)