From b59f36aad8576ca0ab7a7ecac345d6483d818d3e Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Mon, 16 Mar 2020 12:25:38 -0400
Subject: FindPkgConfig: Unset results when pkg-config is broken

Inspired-by: FUJI Goro <goro@fastly.com>
---
 Modules/FindPkgConfig.cmake | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/Modules/FindPkgConfig.cmake b/Modules/FindPkgConfig.cmake
index c79f20f..b7e6442 100644
--- a/Modules/FindPkgConfig.cmake
+++ b/Modules/FindPkgConfig.cmake
@@ -34,16 +34,31 @@ endif()
 find_program(PKG_CONFIG_EXECUTABLE NAMES pkg-config DOC "pkg-config executable")
 mark_as_advanced(PKG_CONFIG_EXECUTABLE)
 
+set(_PKG_CONFIG_FAILURE_MESSAGE "")
 if (PKG_CONFIG_EXECUTABLE)
   execute_process(COMMAND ${PKG_CONFIG_EXECUTABLE} --version
-    OUTPUT_VARIABLE PKG_CONFIG_VERSION_STRING
-    ERROR_QUIET
-    OUTPUT_STRIP_TRAILING_WHITESPACE)
+    OUTPUT_VARIABLE PKG_CONFIG_VERSION_STRING OUTPUT_STRIP_TRAILING_WHITESPACE
+    ERROR_VARIABLE _PKG_CONFIG_VERSION_ERROR ERROR_STRIP_TRAILING_WHITESPACE
+    RESULT_VARIABLE _PKG_CONFIG_VERSION_RESULT
+    )
+
+  if (NOT _PKG_CONFIG_VERSION_RESULT EQUAL 0)
+    string(REPLACE "\n" "\n    " _PKG_CONFIG_VERSION_ERROR "      ${_PKG_CONFIG_VERSION_ERROR}")
+    string(APPEND _PKG_CONFIG_FAILURE_MESSAGE
+      "The command\n"
+      "      \"${PKG_CONFIG_EXECUTABLE}\" --version\n"
+      "    failed with output\n${_PKG_CONFIG_VERSION_ERROR}"
+      )
+    set(PKG_CONFIG_EXECUTABLE "")
+    unset(PKG_CONFIG_VERSION_STRING)
+  endif ()
+  unset(_PKG_CONFIG_VERSION_RESULT)
 endif ()
 
 include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
 find_package_handle_standard_args(PkgConfig
                                   REQUIRED_VARS PKG_CONFIG_EXECUTABLE
+                                  REASON_FAILURE_MESSAGE "${_PKG_CONFIG_FAILURE_MESSAGE}"
                                   VERSION_VAR PKG_CONFIG_VERSION_STRING)
 
 # This is needed because the module name is "PkgConfig" but the name of
-- 
cgit v0.12


From 1c99f5df288dbc8a79a38b20db9ff319eb456fe8 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 17 Mar 2020 08:02:15 -0400
Subject: FindPkgConfig: Add test for specified pkg-config tool missing

---
 Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist-stdout.txt | 6 ++++++
 Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist.cmake      | 4 ++++
 Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake               | 2 ++
 3 files changed, 12 insertions(+)
 create mode 100644 Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist-stdout.txt
 create mode 100644 Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist.cmake

diff --git a/Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist-stdout.txt b/Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist-stdout.txt
new file mode 100644
index 0000000..ef5f7f6
--- /dev/null
+++ b/Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist-stdout.txt
@@ -0,0 +1,6 @@
+-- Could NOT find PkgConfig \(missing: PKG_CONFIG_EXECUTABLE\) *
+    Reason given by package: The command
+      "pkg-config-does-not-exist" --version
+    failed with output.*
+-- PKG_CONFIG_FOUND='FALSE'
+-- PKG_CONFIG_EXECUTABLE=''
diff --git a/Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist.cmake b/Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist.cmake
new file mode 100644
index 0000000..a4fabde
--- /dev/null
+++ b/Tests/RunCMake/FindPkgConfig/PkgConfigDoesNotExist.cmake
@@ -0,0 +1,4 @@
+set(PKG_CONFIG_EXECUTABLE "pkg-config-does-not-exist" CACHE FILEPATH "")
+find_package(PkgConfig)
+message(STATUS "PKG_CONFIG_FOUND='${PKG_CONFIG_FOUND}'")
+message(STATUS "PKG_CONFIG_EXECUTABLE='${PKG_CONFIG_EXECUTABLE}'")
diff --git a/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake b/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake
index b77bb54..9df1d5b 100644
--- a/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake
+++ b/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake
@@ -1,5 +1,7 @@
 include(RunCMake)
 
+run_cmake(PkgConfigDoesNotExist)
+
 run_cmake(FindPkgConfig_NO_PKGCONFIG_PATH)
 run_cmake(FindPkgConfig_PKGCONFIG_PATH)
 run_cmake(FindPkgConfig_PKGCONFIG_PATH_NO_CMAKE_PATH)
-- 
cgit v0.12