[gdb/python] Normalize exceptions in gdbpy_err_fetch

With python 3.12, I run into:
...
(gdb) PASS: gdb.python/py-block.exp: check variable access
python print (block['nonexistent'])^M
Python Exception <class 'KeyError'>: 'nonexistent'^M
Error occurred in Python: 'nonexistent'^M
(gdb) FAIL: gdb.python/py-block.exp: check nonexistent variable
...

The problem is that that PyErr_Fetch returns a normalized exception, while the
test-case matches the output for an unnormalized exception.

With python 3.6, PyErr_Fetch returns an unnormalized exception, and the
test passes.

Fix this by:
- updating the test-case to match the output for a normalized exception, and
- lazily forcing normalized exceptions using PyErr_NormalizeException.

Tested on aarch64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

2 files changed, 15 insertions, 2 deletions

diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 9ceb4aa..30802ae 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -683,6 +683,18 @@ public:
 
   gdbpy_ref<> value () const
   {
+    if (!m_normalized)
+      {
+	PyObject *error_type, *error_value, *error_traceback;
+	error_type = m_error_type.release ();
+	error_value = m_error_value.release ();
+	error_traceback = m_error_traceback.release ();
+	PyErr_NormalizeException (&error_type, &error_value, &error_traceback);
+	m_error_type.reset (error_type);
+	m_error_value.reset (error_value);
+	m_error_traceback.reset (error_traceback);
+	m_normalized = true;
+      }
     return m_error_value;
   }
 
@@ -695,7 +707,8 @@ public:
 
 private:
 
-  gdbpy_ref<> m_error_type, m_error_value, m_error_traceback;
+  mutable gdbpy_ref<> m_error_type, m_error_value, m_error_traceback;
+  mutable bool m_normalized = false;
 };
 
 /* Called before entering the Python interpreter to install the
diff --git a/gdb/testsuite/gdb.python/py-block.exp b/gdb/testsuite/gdb.python/py-block.exp
index 942611a..99642a5 100644
--- a/gdb/testsuite/gdb.python/py-block.exp
+++ b/gdb/testsuite/gdb.python/py-block.exp
@@ -44,7 +44,7 @@ gdb_test "python print (block.function)" "None" "first anonymous block"
 gdb_test "python print (block.start)" "${decimal}" "check start not None"
 gdb_test "python print (block.end)" "${decimal}" "check end not None"
 gdb_test "python print (block\['f'\].name == 'f')" "True" "check variable access"
-gdb_test "python print (block\['nonexistent'\])" ".*KeyError.*: nonexistent.*" \
+gdb_test "python print (block\['nonexistent'\])" ".*KeyError.*: 'nonexistent'.*" \
          "check nonexistent variable"
 gdb_test "python print (block\[42\])" ".*TypeError.*: Expected a string.*" \
          "check non-string key"