[llvm-branch-commits] [libcxx] 0cd4bab - Reapply [libcxx] [modules] Fix relative paths with absolute LIBCXX_INSTALL_MODULES_DIR (#86020)

[Tom Stellard via llvm-branch-commits]

Author: Martin Storsjö
Date: 2024-03-28T14:18:41-07:00
New Revision: 0cd4babe0342c994d28916ecbbb7cd2b91023b9b

URL: https://github.com/llvm/llvm-project/commit/0cd4babe0342c994d28916ecbbb7cd2b91023b9b
DIFF: https://github.com/llvm/llvm-project/commit/0cd4babe0342c994d28916ecbbb7cd2b91023b9b.diff

LOG: Reapply [libcxx] [modules] Fix relative paths with absolute LIBCXX_INSTALL_MODULES_DIR (#86020)

This reapplies 272d1b44efdedb68c194970a610f0ca1b7b769c5 (from #85756),
which was reverted in
407937036fa7640f61f225474b1ea6623a40dbdd.

In the previous attempt, empty CMAKE_INSTALL_PREFIX was handled by
quoting them, in d209d1340b99d4fbd325dffb5e13b757ab8264ea. That made the
calls to cmake_path(ABSOLUTE_PATH) succeed, but the output paths of that
weren't actually absolute, which was required by file(RELATIVE_PATH).

Avoid this issue by constructing a non-empty base directory variable
to use for calculating the relative path.

(cherry picked from commit 50801f1095d33e712c3a51fdeef82569bd09007f)

Added: 
    

Modified: 
    libcxx/modules/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/libcxx/modules/CMakeLists.txt b/libcxx/modules/CMakeLists.txt
index 0dea8cfca94ac3..d47d19a4755317 100644
--- a/libcxx/modules/CMakeLists.txt
+++ b/libcxx/modules/CMakeLists.txt
@@ -206,9 +206,20 @@ 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 
diff erent location.
+if("${CMAKE_INSTALL_PREFIX}" STREQUAL "")
+  set(BASE_DIRECTORY "/")
+else()
+  set(BASE_DIRECTORY ${CMAKE_INSTALL_PREFIX})
+endif()
+cmake_path(ABSOLUTE_PATH LIBCXX_INSTALL_LIBRARY_DIR
+  BASE_DIRECTORY ${BASE_DIRECTORY}
+  OUTPUT_VARIABLE ABS_LIBRARY_DIR)
+cmake_path(ABSOLUTE_PATH LIBCXX_INSTALL_MODULES_DIR
+  BASE_DIRECTORY ${BASE_DIRECTORY}
+  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"