From 1f95e8ac9cf07059abcd926e4005b1606f837a05 Mon Sep 17 00:00:00 2001
From: Steve Gerbino <steve@gerbino.co>
Date: Mon, 23 Feb 2026 23:51:25 +0100
Subject: [PATCH] Fix INSTALL_INTERFACE for Boost versioned-layout installs on
 Windows

boost_install's __boost_install_update_include_directory expects
either a raw path or $<BUILD_INTERFACE:path> to replace with the
correct $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>. When
INSTALL_INTERFACE was already set, the pattern match failed and
the versioned include path (include/boost-X_Y) was never applied.
---
 CMakeLists.txt | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8ce984e3..a1cf7b2d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,6 +3,7 @@
 # Copyright (c) 2021 Dmitry Arkhipov (grisumbras@gmail.com)
 # Copyright (c) 2022 Alan de Freitas (alandefreitas@gmail.com)
 # Copyright (c) 2025 Mohammad Nejati
+# Copyright (c) 2026 Steve Gerbino
 #
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -43,8 +44,7 @@ source_group(TREE ${CMAKE_CURRENT_SOURCE_DIR}/src PREFIX "src" FILES ${BOOST_CAP
 function(boost_capy_setup_properties target)
     target_compile_features(${target} PUBLIC cxx_std_20)
     target_include_directories(${target} PUBLIC
-        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-        $<INSTALL_INTERFACE:include>)
+        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>)
     target_include_directories(${target} PRIVATE
         $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>)
     target_compile_definitions(${target} PUBLIC BOOST_CAPY_NO_LIB)
@@ -87,6 +87,11 @@ else()
     include(GNUInstallDirs)
     include(CMakePackageConfigHelpers)
 
+    # Set INSTALL_INTERFACE for standalone installs (boost_install handles
+    # this for superproject builds, including versioned-layout paths)
+    target_include_directories(boost_capy PUBLIC
+        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
+
     set(BOOST_CAPY_INSTALL_CMAKEDIR
         ${CMAKE_INSTALL_LIBDIR}/cmake/boost_capy)