From adfb0623cb68e59a398816f34fa43386adbc46e9 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Wed, 18 Dec 2024 09:37:59 -0500
Subject: [PATCH] find_package: Fix assertion failure on empty sysroots

Previously we crashed if at least one root variable was set to empty and
at least one to non-empty.

Fixes: #26538
---
 Source/cmFindCommon.cxx                        |  8 ++++----
 Tests/RunCMake/find_package/EmptyRoots.cmake   | 10 ++++++++++
 Tests/RunCMake/find_package/RunCMakeTest.cmake |  1 +
 3 files changed, 15 insertions(+), 4 deletions(-)
 create mode 100644 Tests/RunCMake/find_package/EmptyRoots.cmake

diff --git a/Source/cmFindCommon.cxx b/Source/cmFindCommon.cxx
index 01c87c2ed1..f57564e02d 100644
--- a/Source/cmFindCommon.cxx
+++ b/Source/cmFindCommon.cxx
@@ -248,19 +248,19 @@ void cmFindCommon::RerootPaths(std::vector<std::string>& paths,
   // Construct the list of path roots with no trailing slashes.
   cmList roots;
   debugRoot("CMAKE_FIND_ROOT_PATH", rootPath);
-  if (rootPath) {
+  if (cmNonempty(rootPath)) {
     roots.assign(*rootPath);
   }
   debugRoot("CMAKE_SYSROOT_COMPILE", sysrootCompile);
-  if (sysrootCompile) {
+  if (cmNonempty(sysrootCompile)) {
     roots.emplace_back(*sysrootCompile);
   }
   debugRoot("CMAKE_SYSROOT_LINK", sysrootLink);
-  if (sysrootLink) {
+  if (cmNonempty(sysrootLink)) {
     roots.emplace_back(*sysrootLink);
   }
   debugRoot("CMAKE_SYSROOT", sysroot);
-  if (sysroot) {
+  if (cmNonempty(sysroot)) {
     roots.emplace_back(*sysroot);
   }
   for (auto& r : roots) {
diff --git a/Tests/RunCMake/find_package/EmptyRoots.cmake b/Tests/RunCMake/find_package/EmptyRoots.cmake
new file mode 100644
index 0000000000..22d4e1668d
--- /dev/null
+++ b/Tests/RunCMake/find_package/EmptyRoots.cmake
@@ -0,0 +1,10 @@
+set(vars CMAKE_SYSROOT CMAKE_SYSROOT_COMPILE CMAKE_SYSROOT_LINK CMAKE_FIND_ROOT_PATH)
+foreach(v IN LISTS vars)
+  set("${v}" "")
+endforeach()
+foreach(v IN LISTS vars)
+  block()
+    set("${v}" "/dummy")
+    find_package(dummy CONFIG NO_DEFAULT_PATH PATHS "/")
+  endblock()
+endforeach()
diff --git a/Tests/RunCMake/find_package/RunCMakeTest.cmake b/Tests/RunCMake/find_package/RunCMakeTest.cmake
index 1995ac40b2..0552535e61 100644
--- a/Tests/RunCMake/find_package/RunCMakeTest.cmake
+++ b/Tests/RunCMake/find_package/RunCMakeTest.cmake
@@ -3,6 +3,7 @@ include(RunCMake)
 run_cmake(CMP0074-WARN)
 run_cmake(CMP0074-OLD)
 run_cmake(ComponentRequiredAndOptional)
+run_cmake(EmptyRoots)
 run_cmake(FromPATHEnv)
 run_cmake_with_options(FromPATHEnvDebugPkg --debug-find-pkg=Resolved)
 run_cmake(FromPrefixPath)