Improved bitness Exception handling in Linux and related docs

3 files changed, 37 insertions, 16 deletions

diff --git a/docs/faq.rst b/docs/faq.rst
index 28da727..11796e2 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -60,12 +60,24 @@ Error: No matching architecture
 -------------------------------
 
 This error occurs when you the Python architecture does not match the VISA
-architecture. It is common on Mac OS X and the error message looks like this::
+architecture.
+
+.. note:: PyVISA tries to parse the error from the underlying foreign function
+   library to provide a more useful error message. If it does not succeed, it
+   shows the original one.
+
+   In Mac OS X the original error message looks like this::
 
     OSError: dlopen(/Library/Frameworks/visa.framework/visa, 6): no suitable image found.  Did find:
         /Library/Frameworks/visa.framework/visa: no matching architecture in universal wrapper
         /Library/Frameworks/visa.framework/visa: no matching architecture in universal wrapper
 
+   In Linux the original error message looks like this::
+
+    OSError: Could not open VISA library:
+        Error while accessing /usr/local/vxipnp/linux/bin/libvisa.so.7:/usr/local/vxipnp/linux/bin/libvisa.so.7: wrong ELF class: ELFCLASS32
+
+
 First, determine the details of your installation with the help of the following debug command::
 
     python -c "from pyvisa import util; util.get_debug_info()"
diff --git a/docs/getting.rst b/docs/getting.rst
index c36dfa2..64b91b6 100644
--- a/docs/getting.rst
+++ b/docs/getting.rst
@@ -7,6 +7,10 @@ PyVISA is a wrapper around the `National Instruments's VISA` library, which you
 
 PyVISA has no additional dependencies except Python_ itself. In runs on Python 2.6+ and 3.2+.
 
+.. warning:: PyVISA works with 32- and 64- bit Python and can deal with 32- and 64-bit VISA libraries without any extra configuration. What PyVISA cannot do is open a 32-bit VISA library while running in 64-bit Python (or the other way around).
+
+   **You need to make sure that the Python and VISA library have the same bitness**
+
 You can install it using pip_::
 
     $ pip install pyvisa
diff --git a/pyvisa/errors.py b/pyvisa/errors.py
index 42a9365..87d4519 100644
--- a/pyvisa/errors.py
+++ b/pyvisa/errors.py
@@ -426,24 +426,29 @@ class LibraryError(OSError, Error):
 
         msg = str(exc)
 
-        s = 'Error while accessing %s:' % filename
-
         if ': image not found' in msg:
-            s += ' File not found or not readable.'
+            msg = ' File not found or not readable.'
 
         elif ': no suitable image found' in msg:
             if 'no matching architecture' in msg:
-                details = util.get_system_details(visa=False)
-                visalib = util.LibraryPath(filename, 'user' if filename == util.read_user_library_path() else 'auto')
-                s += ' No matching architecture.\n'
-                s += '    Current Python interpreter is %s bits\n' % details['bits']
-                s += '    The library in: %s\n' % visalib.path
-                s += '      found by: %s\n' % visalib.found_by
-                s += '      32bit: %s\n' % visalib.is_32bit
-                s += '      64bit: %s' % visalib.is_64bit
+                return LibraryError.from_wrong_arch(filename)
             else:
-                s += ' Could not determine file type.'
-        else:
-            s += str(exc)
+                msg = 'Could not determine filetype.'
+                
+        elif 'wrong ELF class' in msg:
+            return LibraryError.from_wrong_arch(filename)
+
+        return cls('Error while accessing %s: %s' % (filename, msg))
 
-        return cls(s)
+    @classmethod
+    def from_wrong_arch(cls, filename):
+        s = ''
+        details = util.get_system_details(visa=False)
+        visalib = util.LibraryPath(filename, 'user' if filename == util.read_user_library_path() else 'auto')
+        s += 'No matching architecture.\n'
+        s += '    Current Python interpreter is %s bits\n' % details['bits']
+        s += '    The library in: %s\n' % visalib.path
+        s += '      found by: %s\n' % visalib.found_by
+        s += '      bitness: %s\n' % visalib.bitness
+
+        return cls('Error while accessing %s: %s' % (filename, s))