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Find Haskell exception source

I am trying to figure out where the exception is thrown. This is my first experience with exception handling in Haskell. I am trying to call the XML-RPC function on a remote host accessed using https:

ghci> import Network.XmlRpc.Client ghci> import Network.XmlRpc.Internals ghci> remote "https://rpc.ote.gandi.net/xmlrpc/" "domain.count" (ValueString "01234567890ABCDEF") *** Exception: user error (https not supported)

To find out if I forgot to enable SSL support in some package or if it is something else, I would like to know which package throws an exception.

I started by following the instructions in the GHC docs , but it doesn't work as expected:

 ghci> :set -fbreak-on-exception ghci> :trace remote "https://rpc.ote.gandi.net/xmlrpc/" "domain.count" (ValueString "01234567890ABCDEF") Stopped at <exception thrown> _exception :: e = _ ghci> :hist Empty history. Perhaps you forgot to use :trace?

All relevant packages must be compiled with --enable-library-profiling .

How to find an exception?

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The reason you cannot get good information is because :trace cannot enter the library code - we need to interpret any code that we want to track. Whether it was compiled with profiling does not matter. After installing some dependencies, I did this to get more information:

  % cabal unpack haxr % cd haxr-3000.8.5 % ghci Network/XmlRpc/Client.hs -XOverlappingInstances -XTypeSynonymInstances -XFlexibleInstances -XTemplateHaskell *Network.XmlRpc.Client> :set -fbreak-on-exception *Network.XmlRpc.Client> :trace remote "https://rpc.ote.gandi.net/xmlrpc/" "domain.count" (ValueString "01234567890ABCDEF") Stopped at <exception thrown> _exception :: e = _ [<exception thrown>] *Network.XmlRpc.Client> :hist -1 : authHdr (Network/XmlRpc/Client.hs:169:27-33) -2 : request:parseUserInfo (Network/XmlRpc/Client.hs:161:34-40) -3 : request:parseUserInfo (Network/XmlRpc/Client.hs:161:31-73) -4 : request:parseUserInfo:(...) (Network/XmlRpc/Client.hs:159:55-70) -5 : request:parseUserInfo:(...) (Network/XmlRpc/Client.hs:159:39-51) -6 : request:parseUserInfo:(...) (Network/XmlRpc/Client.hs:159:39-70) -7 : request:parseUserInfo (Network/XmlRpc/Client.hs:160:34-39) -8 : request:parseUserInfo (Network/XmlRpc/Client.hs:160:31-64) -9 : request:parseUserInfo (Network/XmlRpc/Client.hs:(160,29)-(161,74)) -10 : request:parseUserInfo (Network/XmlRpc/Client.hs:(159,5)-(161,74)) -11 : authHdr (Network/XmlRpc/Client.hs:(169,1)-(175,60)) -12 : request:headers (Network/XmlRpc/Client.hs:158:33-47) -13 : request:headers (Network/XmlRpc/Client.hs:158:33-63) -14 : request:headers (Network/XmlRpc/Client.hs:158:33-70) -15 : request:headers (Network/XmlRpc/Client.hs:158:20-71) -16 : request:headers (Network/XmlRpc/Client.hs:157:16-65) -17 : request:headers (Network/XmlRpc/Client.hs:156:16-47) -18 : request:headers (Network/XmlRpc/Client.hs:155:16-44) -19 : request:headers (Network/XmlRpc/Client.hs:(155,15)-(158,71)) -20 : request (Network/XmlRpc/Client.hs:(149,28)-(152,54)) ...

Hope this helps you. You may find that this will lead you to the other edge of the library - if so, you will need to unzip and interpret this library to go deeper. Good luck

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