From ed19ebd789e92014a87917980700c0663c37fe30 Mon Sep 17 00:00:00 2001
From: Mark Callow <github@callow.im>
Date: Sat, 25 Nov 2023 19:01:41 +0900
Subject: [PATCH 1/2] Set tools and tests rpath on Linux.

---
 tests/CMakeLists.txt | 4 ++++
 tools/CMakeLists.txt | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 49910cec6f..400154ea70 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -6,6 +6,10 @@ function(set_test_properties test_target)
         set_target_properties(${test_target} PROPERTIES
             INSTALL_RPATH "@executable_path;/usr/local/lib"
         )
+    elseif(LINUX)
+        set_target_properties(${test_target} PROPERTIES
+            INSTALL_RPATH "$ORIGIN;$ORIGIN/../lib"
+        )
     endif()
 endfunction()
 
diff --git a/tools/CMakeLists.txt b/tools/CMakeLists.txt
index ae3ef4f950..f1a1c52221 100644
--- a/tools/CMakeLists.txt
+++ b/tools/CMakeLists.txt
@@ -18,6 +18,10 @@ function(set_tool_properties tool_target)
             INSTALL_RPATH "@executable_path;/usr/local/lib"
             CXX_VISIBILITY_PRESET ${STATIC_APP_LIB_SYMBOL_VISIBILITY}
         )
+    elseif(LINUX)
+        set_target_properties(${tool_target} PROPERTIES
+            INSTALL_RPATH "$ORIGIN;$ORIGIN/../lib"
+        )
     endif()
 endfunction()
 

From 71765d2c28b57c374cb560d9706e3e756ec151d3 Mon Sep 17 00:00:00 2001
From: Mark Callow <github@callow.im>
Date: Sun, 26 Nov 2023 18:04:15 +0900
Subject: [PATCH 2/2] Add explanatory comments.

---
 tests/CMakeLists.txt |  1 +
 tools/CMakeLists.txt | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 400154ea70..e02a2b7aa0 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 function(set_test_properties test_target)
+    # See comments in set_tools_properties() in ../tools/CMakeLists.txt.
     if(APPLE)
         set_target_properties(${test_target} PROPERTIES
             INSTALL_RPATH "@executable_path;/usr/local/lib"
diff --git a/tools/CMakeLists.txt b/tools/CMakeLists.txt
index f1a1c52221..ffc1e365dd 100644
--- a/tools/CMakeLists.txt
+++ b/tools/CMakeLists.txt
@@ -15,11 +15,33 @@ function(set_tool_properties tool_target)
     if(APPLE)
         set_target_properties(${tool_target} PROPERTIES
             XCODE_ATTRIBUTE_ENABLE_HARDENED_RUNTIME "YES"
+            # Creates an LC_RPATH entry in the Mac-O binary for each
+            # item in this list. When searching for libraries whose
+            # install name starts with @rpath, as libktx's does, dyld
+            # searches each LC_RPATH in the order given here.
+            #
+            # Check the LC_RPATH entries with
+            # - otool -l <file> | grep -A 3 LC_RPATH
+            #
+            # TODO: Consider adding @executable_path/../lib.
             INSTALL_RPATH "@executable_path;/usr/local/lib"
             CXX_VISIBILITY_PRESET ${STATIC_APP_LIB_SYMBOL_VISIBILITY}
         )
     elseif(LINUX)
         set_target_properties(${tool_target} PROPERTIES
+            # With modern tools sets DT_RUNPATH not the deprecated
+            # DT_RPATH in ELF binaries.  ld.so searches for libraries
+            # as follows:
+            # - LD_LIBRARY_PATH
+            # - RUNPATH
+            # - Directories given in /etc/ld.so.conf.
+            #   /usr/local/lib is listed there.
+            # - Default path: /lib;/usr/lib.
+            # $ORIGIN is equivalent to @executable_path.
+            #
+            # Check DT_RUNPATH with one of
+            # - readelf -d <file> | head -20
+            # - objdump -x <file> | grep 'R.*PATH'
             INSTALL_RPATH "$ORIGIN;$ORIGIN/../lib"
         )
     endif()