From 93f77d8183bbe5a215385cd4bc7da2f83c9776d7 Mon Sep 17 00:00:00 2001
From: Vito Gamberini <vito.gamberini@kitware.com>
Date: Wed, 13 Aug 2025 11:56:58 -0400
Subject: [PATCH] PkgC: Allow system paths during IMPORT, POPULATE

Fixes: #27138
---
 Source/cmCMakePkgConfigCommand.cxx                   |  3 +++
 .../cmake_pkg_config/ImportSystem-check.cmake        | 11 +++++++++++
 Tests/RunCMake/cmake_pkg_config/ImportSystem.cmake   | 12 ++++++++++++
 Tests/RunCMake/cmake_pkg_config/RunCMakeTest.cmake   |  1 +
 4 files changed, 27 insertions(+)
 create mode 100644 Tests/RunCMake/cmake_pkg_config/ImportSystem-check.cmake
 create mode 100644 Tests/RunCMake/cmake_pkg_config/ImportSystem.cmake

diff --git a/Source/cmCMakePkgConfigCommand.cxx b/Source/cmCMakePkgConfigCommand.cxx
index 181c7d8624..0d753bb86e 100644
--- a/Source/cmCMakePkgConfigCommand.cxx
+++ b/Source/cmCMakePkgConfigCommand.cxx
@@ -911,6 +911,9 @@ std::pair<bool, bool> PopulatePCTarget(PopulateArguments& args,
   auto& pcEnv = maybeEnv->first;
   auto& imEnv = maybeEnv->second;
 
+  pcEnv.AllowSysCflags = true;
+  pcEnv.AllowSysLibs = true;
+
   pkgProviders providers;
   if (args.Providers) {
     for (auto const& provider_str : *args.Providers) {
diff --git a/Tests/RunCMake/cmake_pkg_config/ImportSystem-check.cmake b/Tests/RunCMake/cmake_pkg_config/ImportSystem-check.cmake
new file mode 100644
index 0000000000..a6f4eb3f07
--- /dev/null
+++ b/Tests/RunCMake/cmake_pkg_config/ImportSystem-check.cmake
@@ -0,0 +1,11 @@
+set(expected
+"Include Directories: /TestDirectories/Include
+Link Directories: /TestDirectories/Library
+"
+)
+
+file(READ "${RunCMake_TEST_BINARY_DIR}/import-system.txt" actual)
+
+if(NOT(expected STREQUAL actual))
+  set(RunCMake_TEST_FAILED "cmake_pkg_config import-system.txt does not match expected:\n${actual}")
+endif()
diff --git a/Tests/RunCMake/cmake_pkg_config/ImportSystem.cmake b/Tests/RunCMake/cmake_pkg_config/ImportSystem.cmake
new file mode 100644
index 0000000000..bf0fb1468b
--- /dev/null
+++ b/Tests/RunCMake/cmake_pkg_config/ImportSystem.cmake
@@ -0,0 +1,12 @@
+set(CMAKE_PKG_CONFIG_SYS_INCLUDE_DIRS /TestDirectories/Include)
+set(CMAKE_PKG_CONFIG_SYS_LIB_DIRS /TestDirectories/Library)
+
+cmake_pkg_config(IMPORT import-simple REQUIRED)
+
+file(GENERATE
+  OUTPUT import-system.txt
+  CONTENT
+"Include Directories: $<TARGET_PROPERTY:PkgConfig::import-simple,INTERFACE_INCLUDE_DIRECTORIES>
+Link Directories: $<TARGET_PROPERTY:PkgConfig::import-simple,INTERFACE_LINK_DIRECTORIES>
+"
+)
diff --git a/Tests/RunCMake/cmake_pkg_config/RunCMakeTest.cmake b/Tests/RunCMake/cmake_pkg_config/RunCMakeTest.cmake
index 422a993fdd..b2e38fc2f5 100644
--- a/Tests/RunCMake/cmake_pkg_config/RunCMakeTest.cmake
+++ b/Tests/RunCMake/cmake_pkg_config/RunCMakeTest.cmake
@@ -20,6 +20,7 @@ run_cmake(ImportName)
 run_cmake(ImportPrefix)
 run_cmake(ImportRequires)
 run_cmake(ImportSimple)
+run_cmake(ImportSystem)
 run_cmake(ImportTransitiveFail)
 run_cmake(ImportTransitiveVersion)
 run_cmake(ImportTransitiveVersionFail)