CMakePackageConfigHelpers: Add ARCH_INDEPENDENT option

Allow skipping the architecture check in the package version file generated from calling
write_basic_package_version_file. Document said architecture check.

Fixes: #16184

6 files changed, 37 insertions, 2 deletions

diff --git a/Modules/BasicConfigVersion-AnyNewerVersion.cmake.in b/Modules/BasicConfigVersion-AnyNewerVersion.cmake.in
index bc78016..afffc04 100644
--- a/Modules/BasicConfigVersion-AnyNewerVersion.cmake.in
+++ b/Modules/BasicConfigVersion-AnyNewerVersion.cmake.in
@@ -18,6 +18,12 @@ else()
   endif()
 endif()
 
+
+# if the installed project requested no architecture check, don't perform the check
+if("@CVF_ARCH_INDEPENDENT@")
+  return()
+endif()
+
 # if the installed or the using project don't have CMAKE_SIZEOF_VOID_P set, ignore it:
 if("${CMAKE_SIZEOF_VOID_P}" STREQUAL "" OR "@CMAKE_SIZEOF_VOID_P@" STREQUAL "")
    return()
diff --git a/Modules/BasicConfigVersion-ExactVersion.cmake.in b/Modules/BasicConfigVersion-ExactVersion.cmake.in
index de4a23a..fe5c2e5 100644
--- a/Modules/BasicConfigVersion-ExactVersion.cmake.in
+++ b/Modules/BasicConfigVersion-ExactVersion.cmake.in
@@ -34,6 +34,11 @@ if(PACKAGE_FIND_VERSION STREQUAL PACKAGE_VERSION)
 endif()
 
 
+# if the installed project requested no architecture check, don't perform the check
+if("@CVF_ARCH_INDEPENDENT@")
+  return()
+endif()
+
 # if the installed or the using project don't have CMAKE_SIZEOF_VOID_P set, ignore it:
 if("${CMAKE_SIZEOF_VOID_P}" STREQUAL "" OR "@CMAKE_SIZEOF_VOID_P@" STREQUAL "")
    return()
diff --git a/Modules/BasicConfigVersion-SameMajorVersion.cmake.in b/Modules/BasicConfigVersion-SameMajorVersion.cmake.in
index a32245d..d885c0f 100644
--- a/Modules/BasicConfigVersion-SameMajorVersion.cmake.in
+++ b/Modules/BasicConfigVersion-SameMajorVersion.cmake.in
@@ -33,6 +33,11 @@ else()
 endif()
 
 
+# if the installed project requested no architecture check, don't perform the check
+if("@CVF_ARCH_INDEPENDENT@")
+  return()
+endif()
+
 # if the installed or the using project don't have CMAKE_SIZEOF_VOID_P set, ignore it:
 if("${CMAKE_SIZEOF_VOID_P}" STREQUAL "" OR "@CMAKE_SIZEOF_VOID_P@" STREQUAL "")
    return()
diff --git a/Modules/BasicConfigVersion-SameMinorVersion.cmake.in b/Modules/BasicConfigVersion-SameMinorVersion.cmake.in
index 59ca253..bf055e8 100644
--- a/Modules/BasicConfigVersion-SameMinorVersion.cmake.in
+++ b/Modules/BasicConfigVersion-SameMinorVersion.cmake.in
@@ -37,6 +37,11 @@ else()
 endif()
 
 
+# if the installed project requested no architecture check, don't perform the check
+if("@CVF_ARCH_INDEPENDENT@")
+  return()
+endif()
+
 # if the installed or the using project don't have CMAKE_SIZEOF_VOID_P set, ignore it:
 if("${CMAKE_SIZEOF_VOID_P}" STREQUAL "" OR "@CMAKE_SIZEOF_VOID_P@" STREQUAL "")
    return()
diff --git a/Modules/CMakePackageConfigHelpers.cmake b/Modules/CMakePackageConfigHelpers.cmake
index bcc9bf8..22fc953 100644
--- a/Modules/CMakePackageConfigHelpers.cmake
+++ b/Modules/CMakePackageConfigHelpers.cmake
@@ -124,7 +124,8 @@ Generating a Package Version File
 
    write_basic_package_version_file(<filename>
      [VERSION <major.minor.patch>]
-     COMPATIBILITY <AnyNewerVersion|SameMajorVersion|SameMinorVersion|ExactVersion> )
+     COMPATIBILITY <AnyNewerVersion|SameMajorVersion|SameMinorVersion|ExactVersion>
+     [ARCH_INDEPENDENT] )
 
 
 Writes a file for use as ``<PackageName>ConfigVersion.cmake`` file to
@@ -158,6 +159,18 @@ If your project has more elaborated version matching rules, you will need to
 write your own custom ``ConfigVersion.cmake`` file instead of using this
 macro.
 
+If ``ARCH_INDEPENDENT`` is given, the installed package version will be
+considered compatible even if it was built for a different architecture than
+the requested architecture.  Otherwise, an architecture check will be performed,
+and the package will be considered compatible only if the architecture matches
+exactly.  For example, if the package is built for a 32-bit architecture, the
+package is only considered compatible if it is used on a 32-bit architecture,
+unless ``ARCH_INDEPENDENT`` is given, in which case the package is considered
+compatible on any architecture.
+
+.. note:: ``ARCH_INDEPENDENT`` is intended for header-only libraries or similar
+   packages with no binaries.
+
 Internally, this macro executes :command:`configure_file()` to create the
 resulting version file.  Depending on the ``COMPATIBILITY``, the corresponding
 ``BasicConfigVersion-<COMPATIBILITY>.cmake.in`` file is used.
diff --git a/Modules/WriteBasicConfigVersionFile.cmake b/Modules/WriteBasicConfigVersionFile.cmake
index 1f13096..45f9e58 100644
--- a/Modules/WriteBasicConfigVersionFile.cmake
+++ b/Modules/WriteBasicConfigVersionFile.cmake
@@ -15,6 +15,7 @@ WriteBasicConfigVersionFile
   WRITE_BASIC_CONFIG_VERSION_FILE( filename
     [VERSION major.minor.patch]
     COMPATIBILITY (AnyNewerVersion|SameMajorVersion|SameMinorVersion|ExactVersion)
+    [ARCH_INDEPENDENT]
     )
 
 
@@ -22,7 +23,7 @@ WriteBasicConfigVersionFile
 
 function(WRITE_BASIC_CONFIG_VERSION_FILE _filename)
 
-  set(options )
+  set(options ARCH_INDEPENDENT )
   set(oneValueArgs VERSION COMPATIBILITY )
   set(multiValueArgs )