[llvm-branch-commits] [libcxx] release/18.x: [libcxx] [modules] Fix relative paths with absolute LIBCXX_INSTALL_MODULES_DIR (#85756) (PR #85907)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/85907

Backport 272d1b44efdedb68c194970a610f0ca1b7b769c5

Requested by: @mstorsjo

>From 7ed553656598a0360901235b9a6c401f82fa07c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Wed, 20 Mar 2024 10:45:43 +0200
Subject: [PATCH] [libcxx] [modules] Fix relative paths with absolute
 LIBCXX_INSTALL_MODULES_DIR (#85756)

In other contexts, install directories such as
LIBCXX_INSTALL_LIBRARY_DIR and LIBCXX_INSTALL_MODULES_DIR can be
specified either as a relative path, relative to CMAKE_INSTALL_PREFIX,
or as an absolute path.

When calculating the relative path between the two, account for the fact
that LIBCXX_INSTALL_MODULES_DIR and LIBCXX_INSTALL_LIBRARY_DIR can be
absolute paths too.

(cherry picked from commit 272d1b44efdedb68c194970a610f0ca1b7b769c5)
---
 libcxx/modules/CMakeLists.txt | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libcxx/modules/CMakeLists.txt b/libcxx/modules/CMakeLists.txt
index 0dea8cfca94ac3..8dd1b51aac2f72 100644
--- a/libcxx/modules/CMakeLists.txt
+++ b/libcxx/modules/CMakeLists.txt
@@ -206,9 +206,15 @@ add_custom_target(generate-cxx-modules
 # Configure the modules manifest.
 # Use the relative path between the installation and the module in the json
 # file. This allows moving the entire installation to a different location.
+cmake_path(ABSOLUTE_PATH LIBCXX_INSTALL_LIBRARY_DIR
+  BASE_DIRECTORY ${CMAKE_INSTALL_PREFIX}
+  OUTPUT_VARIABLE ABS_LIBRARY_DIR)
+cmake_path(ABSOLUTE_PATH LIBCXX_INSTALL_MODULES_DIR
+  BASE_DIRECTORY ${CMAKE_INSTALL_PREFIX}
+  OUTPUT_VARIABLE ABS_MODULES_DIR)
 file(RELATIVE_PATH LIBCXX_MODULE_RELATIVE_PATH
-  ${CMAKE_INSTALL_PREFIX}/${LIBCXX_INSTALL_LIBRARY_DIR}
-  ${CMAKE_INSTALL_PREFIX}/${LIBCXX_INSTALL_MODULES_DIR})
+  ${ABS_LIBRARY_DIR}
+  ${ABS_MODULES_DIR})
 configure_file(
   "modules.json.in"
   "${LIBCXX_LIBRARY_DIR}/libc++.modules.json"