Add warning message in CMakeDependentOption

Development
1

Hi all,

I think, it would be great to add a warning message into CMakeDependentOption.cmake.

For example, if CMakeLists.txt defines:

cmake_dependent_option(USE_A "description" ON "USE_B" OFF)

but users pass -DUSE_B=OFF -DUSE_A=ON, the current behavior is to silently force USE_A to be OFF. A warning message will make it more visible to users, like:

CMake Warning at CMakeDependentOption.cmake:XX (message):
  Option USE_B was explicitly set to ON, but its dependency condition
  "USE_A" is NOT met.  Forcing USE_B to OFF.

Thank you for considering this suggestion.

Best regards,
SY

2

One example implementation could be:

--- CMakeDependentOption.cmake	2026-07-17 13:14:31.917565738 +0800
+++ CMakeDependentOption.cmake	2026-07-17 13:13:03.835053126 +0800
@@ -238,6 +238,16 @@
     else()
       if(${option} MATCHES "^${option}$")
       else()
+        get_property(_CDO_OPTION_TYPE CACHE ${option} PROPERTY TYPE)
+        if(NOT "${_CDO_OPTION_TYPE}" STREQUAL "INTERNAL"
+           AND NOT "${${option}}" STREQUAL "${force}")
+          message(WARNING 
+            "Option ${option} was explicitly set to ${${option}}, "
+            "but its dependency condition \"${depends}\" is NOT met. "
+            "Forcing ${option} to ${force}."
+          )
+        endif()
+        unset(_CDO_OPTION_TYPE)
         set(${option} "${${option}}" CACHE INTERNAL "${doc}")
       endif()
       set(${option} ${force})
3

@Growl1234 warning once as the overridden value is converted to INTERNAL seems reasonable, so long as we also have a way to suppress the warning. Please open an issue to propose the feature and discuss the details, and link it from here.

4

Thank you, I’ve just opened one with the same content.

5

I see CMake Issue 27960, thanks.