Close #20105: set __traceback__ when chaining exceptions in C

2 files changed, 18 insertions, 0 deletions

diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index 8658a58..d4065e0 100644
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -90,6 +90,16 @@ in various ways.  There is a separate error indicator for each thread.
    the class in that case.  If the values are already normalized, nothing happens.
    The delayed normalization is implemented to improve performance.
 
+   .. note::
+
+      This function *does not* implicitly set the ``__traceback__``
+      attribute on the exception value. If setting the traceback
+      appropriately is desired, the following additional snippet is needed::
+
+         if (tb != NULL) {
+           PyException_SetTraceback(val, tb);
+         }
+
 
 .. c:function:: void PyErr_Clear()
 
diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst
index 5d397fe..1d88965 100644
--- a/Doc/whatsnew/3.4.rst
+++ b/Doc/whatsnew/3.4.rst
@@ -264,6 +264,9 @@ name of the codec responsible for producing the error::
     >>> import codecs
 
     >>> codecs.decode(b"abcdefgh", "hex")
+    Traceback (most recent call last):
+      File "/usr/lib/python3.4/encodings/hex_codec.py", line 20, in hex_decode
+        return (binascii.a2b_hex(input), len(input))
     binascii.Error: Non-hexadecimal digit found
 
     The above exception was the direct cause of the following exception:
@@ -273,6 +276,11 @@ name of the codec responsible for producing the error::
     binascii.Error: decoding with 'hex' codec failed (Error: Non-hexadecimal digit found)
 
     >>> codecs.encode("hello", "bz2")
+    Traceback (most recent call last):
+      File "/usr/lib/python3.4/encodings/bz2_codec.py", line 17, in bz2_encode
+        return (bz2.compress(input), len(input))
+      File "/usr/lib/python3.4/bz2.py", line 498, in compress
+        return comp.compress(data) + comp.flush()
     TypeError: 'str' does not support the buffer interface
 
     The above exception was the direct cause of the following exception: