[PATCH v1] CMake: detect cmocka_version.h via include path, not by linking

From: Lev Stipakov <[email protected]>

check_include_files() was invoked with cmocka in CMAKE_REQUIRED_LIBRARIES,
which makes the probe link the (shared, imported) cmocka library. On some
platforms that link step fails inside the minimal probe, so the header check
reports failure and HAVE_CMOCKA_VERSION_H is left undefined even though
cmocka_version.h is present.

test_common.h then selects its cmocka 1.x compatibility shims and redefines
macros (check_expected_uint, expect_uint_value, ...) that cmocka 2.x already
provides, which breaks the -Werror build of every unit test driver.

Detecting a header only needs the include search path, so pass cmocka's
INTERFACE_INCLUDE_DIRECTORIES via CMAKE_REQUIRED_INCLUDES and drop the library
link requirement from the probe.

Change-Id: Icc14b286f2409738c73873aa7550dcc005ee8cbb
Signed-off-by: Lev Stipakov <[email protected]>
Acked-by: Frank Lichtenheld <[email protected]>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1739
---

This change was reviewed on Gerrit and approved by at least one
developer. I request to merge it to master.

Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1739
This mail reflects revision 1 of this Change.

Acked-by according to Gerrit (reflected above):
Frank Lichtenheld <[email protected]>

        
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4779d69..8de836a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -385,12 +385,20 @@
     find_package(cmocka CONFIG)
     if (TARGET cmocka::cmocka)
         set(CMOCKA_LIBRARIES cmocka::cmocka)
+        get_target_property(CMOCKA_INCLUDE_DIRS cmocka::cmocka INTERFACE_INCLUDE_DIRECTORIES)
     else ()
         pkg_search_module(cmocka cmocka REQUIRED IMPORTED_TARGET)
         set(CMOCKA_LIBRARIES PkgConfig::cmocka)
+        set(CMOCKA_INCLUDE_DIRS ${cmocka_INCLUDE_DIRS})
     endif ()
-    set(CMAKE_REQUIRED_LIBRARIES ${CMOCKA_LIBRARIES})
+    # cmocka_version.h exists since cmocka 2.0; its absence selects the
+    # cmocka 1.x compat shims in test_common.h. Detecting a header only needs
+    # the include path - do NOT add cmocka to CMAKE_REQUIRED_LIBRARIES, as that
+    # makes check_include_files link the shared library, which can fail in the
+    # probe for unrelated reasons and wrongly mis-detect cmocka 2.x as < 2.0.
+    set(CMAKE_REQUIRED_INCLUDES ${CMOCKA_INCLUDE_DIRS})
     check_include_files(cmocka_version.h HAVE_CMOCKA_VERSION_H)
+    unset(CMAKE_REQUIRED_INCLUDES)
 endif ()
 
 configure_file(config.h.cmake.in config.h)