1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
{-# LANGUAGE CPP #-}
module DebuggerUtils (
dataConInfoPtrToName,
) where
import GHCi.InfoTable
import CmmInfo ( stdInfoTableSizeB )
import DynFlags
import FastString
import TcRnTypes
import TcRnMonad
import IfaceEnv
import Module
import OccName
import Name
import Outputable
import Util
import Data.Char
import Foreign
import Data.List
#include "HsVersions.h"
-- | Given a data constructor in the heap, find its Name.
-- The info tables for data constructors have a field which records
-- the source name of the constructor as a Ptr Word8 (UTF-8 encoded
-- string). The format is:
--
-- > Package:Module.Name
--
-- We use this string to lookup the interpreter's internal representation of the name
-- using the lookupOrig.
--
dataConInfoPtrToName :: Ptr () -> TcM (Either String Name)
dataConInfoPtrToName x = do
dflags <- getDynFlags
theString <- liftIO $ do
let ptr = castPtr x :: Ptr StgInfoTable
conDescAddress <- getConDescAddress dflags ptr
peekArray0 0 conDescAddress
let (pkg, mod, occ) = parse theString
pkgFS = mkFastStringByteList pkg
modFS = mkFastStringByteList mod
occFS = mkFastStringByteList occ
occName = mkOccNameFS OccName.dataName occFS
modName = mkModule (fsToUnitId pkgFS) (mkModuleNameFS modFS)
return (Left $ showSDoc dflags $ ppr modName <> dot <> ppr occName)
`recoverM` (Right `fmap` lookupOrig modName occName)
where
{- To find the string in the constructor's info table we need to consider
the layout of info tables relative to the entry code for a closure.
An info table can be next to the entry code for the closure, or it can
be separate. The former (faster) is used in registerised versions of ghc,
and the latter (portable) is for non-registerised versions.
The diagrams below show where the string is to be found relative to
the normal info table of the closure.
1) Code next to table:
--------------
| | <- pointer to the start of the string
--------------
| | <- the (start of the) info table structure
| |
| |
--------------
| entry code |
| .... |
In this case the pointer to the start of the string can be found in
the memory location _one word before_ the first entry in the normal info
table.
2) Code NOT next to table:
--------------
info table structure -> | *------------------> --------------
| | | entry code |
| | | .... |
--------------
ptr to start of str -> | |
--------------
In this case the pointer to the start of the string can be found
in the memory location: info_table_ptr + info_table_size
-}
getConDescAddress :: DynFlags -> Ptr StgInfoTable -> IO (Ptr Word8)
getConDescAddress dflags ptr
| ghciTablesNextToCode = do
let ptr' = ptr `plusPtr` (- wORD_SIZE dflags)
-- NB. the offset must be read as an Int32 not a Word32, so
-- that the sign is preserved when converting to an Int.
offsetToString <- fromIntegral <$> (peek ptr' :: IO Int32)
return $ (ptr `plusPtr` stdInfoTableSizeB dflags) `plusPtr` offsetToString
| otherwise =
peek $ intPtrToPtr $ ptrToIntPtr ptr + fromIntegral (stdInfoTableSizeB dflags)
-- parsing names is a little bit fiddly because we have a string in the form:
-- pkg:A.B.C.foo, and we want to split it into three parts: ("pkg", "A.B.C", "foo").
-- Thus we split at the leftmost colon and the rightmost occurrence of the dot.
-- It would be easier if the string was in the form pkg:A.B.C:foo, but alas
-- this is not the conventional way of writing Haskell names. We stick with
-- convention, even though it makes the parsing code more troublesome.
-- Warning: this code assumes that the string is well formed.
parse :: [Word8] -> ([Word8], [Word8], [Word8])
parse input
= ASSERT(all (`lengthExceeds` 0) ([pkg, mod, occ])) (pkg, mod, occ)
where
dot = fromIntegral (ord '.')
(pkg, rest1) = break (== fromIntegral (ord ':')) input
(mod, occ)
= (concat $ intersperse [dot] $ reverse modWords, occWord)
where
(modWords, occWord) = ASSERT(rest1 `lengthExceeds` 0) (parseModOcc [] (tail rest1))
parseModOcc :: [[Word8]] -> [Word8] -> ([[Word8]], [Word8])
-- We only look for dots if str could start with a module name,
-- i.e. if it starts with an upper case character.
-- Otherwise we might think that "X.:->" is the module name in
-- "X.:->.+", whereas actually "X" is the module name and
-- ":->.+" is a constructor name.
parseModOcc acc str@(c : _)
| isUpper $ chr $ fromIntegral c
= case break (== dot) str of
(top, []) -> (acc, top)
(top, _ : bot) -> parseModOcc (top : acc) bot
parseModOcc acc str = (acc, str)
|
