[PR-182][Bug] Loading library on Aarch64 fails because pylink attempt…

…s to load 32-bit library (#182)

The ARM64 version of the JLink software contains two library files, `libjlinkarm.so` (64 bit)
and `libjlinkarm_arm.so` (32 bit). Pylink attempts to load `libjlinkarm_arm.so` first, which fails
on ARM64 due to the architecture mismatch and causes an error. This change simply
performs a 'test load' of each library file found, skipping if it fails, fixing this issue on ARM64.

pylink/library.py

@@ -138,6 +138,23 @@ def get_appropriate_windows_sdk_name(cls):
         else:
             return Library.WINDOWS_32_JLINK_SDK_NAME
 
+    @classmethod
+    def can_load_library(cls, dllpath):
+        """Test whether a library is the correct architecture to load.
+
+        Args:
+          cls (Library): the ``Library`` class
+          dllpath (str): A path to a library.
+
+        Returns:
+          ``True`` if the library could be successfully loaded, ``False`` if not.
+        """
+        try:
+            ctypes.CDLL(dllpath)
+            return True
+        except OSError:
+            return False
+
     @classmethod
     def find_library_windows(cls):
         """Loads the SEGGER DLL from the windows installation directory.
@@ -203,7 +220,9 @@ def find_library_linux(cls):
             for fname in fnames:
                 fpath = os.path.join(directory_name, fname)
                 if util.is_os_64bit():
-                    if '_x86' not in fname:
+                    if not cls.can_load_library(fpath):
+                        continue
+                    elif '_x86' not in fname:
                         yield fpath
                 elif x86_found:
                     if '_x86' in fname:

tests/unit/test_library.py

@@ -880,13 +880,16 @@ def test_linux_6_10_0_32bit(self, mock_os, mock_load_library, mock_find_library,
     @mock.patch('tempfile.NamedTemporaryFile', new=mock.Mock())
     @mock.patch('ctypes.util.find_library')
     @mock.patch('ctypes.cdll.LoadLibrary')
+    @mock.patch('ctypes.CDLL')
     @mock.patch('pylink.library.os')
-    def test_linux_6_10_0_64bit(self, mock_os, mock_load_library, mock_find_library, mock_open, mock_is_os_64bit):
+    def test_linux_6_10_0_64bit(self, mock_os, mock_cdll, mock_load_library,
+                                mock_find_library, mock_open, mock_is_os_64bit):
         """Tests finding the DLL on Linux through the SEGGER application for V6.0.0+ on 64 bit linux.
 
         Args:
           self (TestLibrary): the ``TestLibrary`` instance
           mock_os (Mock): a mocked version of the ``os`` module
+          mock_cdll (Mock): a mocked version of the `cdll.CDLL` class constructor
           mock_load_library (Mock): a mocked version of the library loader
           mock_find_library (Mock): a mocked call to ``ctypes`` find library
           mock_open (Mock): mock for mocking the call to ``open()``
@@ -896,6 +899,7 @@ def test_linux_6_10_0_64bit(self, mock_os, mock_load_library, mock_find_library,
           ``None``
         """
         mock_find_library.return_value = None
+        mock_cdll.return_value = None
         directories = [
             '/opt/SEGGER/JLink_Linux_V610d_x86_64/libjlinkarm_x86.so.6.10',
             '/opt/SEGGER/JLink_Linux_V610d_x86_64/libjlinkarm.so.6.10',
@@ -918,6 +922,49 @@ def test_linux_6_10_0_64bit(self, mock_os, mock_load_library, mock_find_library,
         lib.unload = mock.Mock()
         self.assertEqual(None, lib._path)
 
+    @mock.patch('sys.platform', new='linux2')
+    @mock.patch('pylink.util.is_os_64bit', return_value=True)
+    @mock.patch('pylink.library.open')
+    @mock.patch('os.remove', new=mock.Mock())
+    @mock.patch('tempfile.NamedTemporaryFile', new=mock.Mock())
+    @mock.patch('ctypes.util.find_library')
+    @mock.patch('ctypes.cdll.LoadLibrary')
+    @mock.patch('ctypes.CDLL')
+    @mock.patch('pylink.library.os')
+    def test_linux_64bit_no_x86(self, mock_os, mock_cdll, mock_load_library,
+                                mock_find_library, mock_open, mock_is_os_64bit):
+        """Tests finding the DLL on Linux when no library name contains 'x86'.
+
+        Args:
+          self (TestLibrary): the ``TestLibrary`` instance
+          mock_os (Mock): a mocked version of the ``os`` module
+          mock_cdll (Mock): a mocked version of the `cdll.CDLL` class constructor
+          mock_load_library (Mock): a mocked version of the library loader
+          mock_find_library (Mock): a mocked call to ``ctypes`` find library
+          mock_open (Mock): mock for mocking the call to ``open()``
+          mock_is_os_64bit (Mock): mock for mocking the call to ``is_os_64bit``, returns True
+
+        Returns:
+          ``None``
+        """
+        def on_cdll(name):
+            if '_arm' in name:
+                raise OSError
+
+        mock_find_library.return_value = None
+        mock_cdll.side_effect = on_cdll
+        directories = [
+            '/opt/SEGGER/JLink_Linux_V610d_x86_64/libjlinkarm_arm.so.6.10',
+            '/opt/SEGGER/JLink_Linux_V610d_x86_64/libjlinkarm.so.6.10',
+        ]
+
+        self.mock_directories(mock_os, directories, '/')
+
+        lib = library.Library()
+        lib.unload = mock.Mock()
+        load_library_args, load_libary_kwargs = mock_load_library.call_args
+        self.assertEqual(directories[1], lib._path)
+
     @mock.patch('sys.platform', new='linux')
     @mock.patch('pylink.library.open')
     @mock.patch('os.remove', new=mock.Mock())
@@ -960,8 +1007,9 @@ def test_linux_empty(self, mock_os, mock_load_library, mock_find_library, mock_o
     @mock.patch('pylink.platform.libc_ver', return_value=('libc', '1.0'))
     @mock.patch('ctypes.util.find_library', return_value='libjlinkarm.so.7')
     @mock.patch('pylink.library.JLinkarmDlInfo.__init__')
+    @mock.patch('ctypes.CDLL')
     @mock.patch('ctypes.cdll.LoadLibrary')
-    def test_linux_glibc_unavailable(self, mock_load_library, mock_dlinfo_ctr, mock_find_library,
+    def test_linux_glibc_unavailable(self, mock_load_library, mock_cdll, mock_dlinfo_ctr, mock_find_library,
                                      mock_libc_ver, mock_is_os_64bit, mock_os,  mock_open):
         """Confirms the whole JLinkarmDlInfo code path is not involved when GNU libc
         extensions are unavailable on a Linux system, and that we'll successfully fallback
@@ -974,6 +1022,7 @@ def test_linux_glibc_unavailable(self, mock_load_library, mock_dlinfo_ctr, mock_
           to the "search by file name" code path, aka find_library_linux()
         - and "successfully load" a mock library file from /opt/SEGGER/JLink
         """
+        mock_cdll.side_effect = None
         directories = [
             # Library.find_library_linux() should find this.
             '/opt/SEGGER/JLink/libjlinkarm.so.6'
@@ -999,8 +1048,9 @@ def test_linux_glibc_unavailable(self, mock_load_library, mock_dlinfo_ctr, mock_
     @mock.patch('pylink.util.is_os_64bit', return_value=True)
     @mock.patch('pylink.platform.libc_ver', return_value=('glibc', '2.34'))
     @mock.patch('ctypes.util.find_library')
+    @mock.patch('ctypes.CDLL')
     @mock.patch('ctypes.cdll.LoadLibrary')
-    def test_linux_dl_unavailable(self, mock_load_library, mock_find_library, mock_libc_ver,
+    def test_linux_dl_unavailable(self, mock_load_library, mock_cdll, mock_find_library, mock_libc_ver,
                                   mock_is_os_64bit, mock_os,  mock_open):
         """Confirms we successfully fallback to the "search by file name" code path when libdl is
         unavailable despite the host system presenting itself as POSIX (GNU/Linux).
@@ -1012,6 +1062,7 @@ def test_linux_dl_unavailable(self, mock_load_library, mock_find_library, mock_l
           to the "search by file name" code path, aka find_library_linux()
         - and "successfully load" a mock library file from /opt/SEGGER/JLink
         """
+        mock_cdll.side_effect = None
         mock_find_library.side_effect = [
             # find_library('jlinkarm')
             'libjlinkarm.so.6',