[commit: base] master: Fix parsing of RealFloat with huge exponents (#7034). (4226bae)

[Paolo Capriotti]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/4226bae42fdd666c15190ac2f8784547d3fbad5f

>---------------------------------------------------------------

commit 4226bae42fdd666c15190ac2f8784547d3fbad5f
Author: Paolo Capriotti <p.capriotti at gmail.com>
Date:   Mon Jul 2 12:54:57 2012 +0100

    Fix parsing of RealFloat with huge exponents (#7034).
    
    Ensure numberToRangedRational returns Nothing immediately if the
    exponent is outside Int range, so that we avoid an integer overflow
    later.

>---------------------------------------------------------------

 Text/Read/Lex.hs   |    8 +++++++-
 tests/T7034.hs     |   11 +++++++++++
 tests/T7034.stdout |    6 ++++++
 tests/all.T        |    2 +-
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Text/Read/Lex.hs b/Text/Read/Lex.hs
index 1a163ee..7c99f0c 100644
--- a/Text/Read/Lex.hs
+++ b/Text/Read/Lex.hs
@@ -44,7 +44,7 @@ import {-# SOURCE #-} GHC.Unicode ( isSpace, isAlpha, isAlphaNum )
 import GHC.Real( Integral, Rational, (%), fromIntegral,
                  toInteger, (^) )
 import GHC.List
-import GHC.Enum( maxBound )
+import GHC.Enum( minBound, maxBound )
 #else
 import Prelude hiding ( lex )
 import Data.Char( chr, ord, isSpace, isAlpha, isAlphaNum )
@@ -96,6 +96,12 @@ numberToInteger _ = Nothing
 numberToRangedRational :: (Int, Int) -> Number
                        -> Maybe Rational -- Nothing = Inf
 numberToRangedRational (neg, pos) n@(MkDecimal iPart mFPart (Just exp))
+    -- if exp is out of integer bounds,
+    -- then the number is definitely out of range
+    | exp > fromIntegral (maxBound :: Int) ||
+      exp < fromIntegral (minBound :: Int)
+    = Nothing
+    | otherwise
     = let mFirstDigit = case dropWhile (0 ==) iPart of
                         iPart'@(_ : _) -> Just (length iPart')
                         [] -> case mFPart of
diff --git a/tests/T7034.hs b/tests/T7034.hs
new file mode 100644
index 0000000..b862bd8
--- /dev/null
+++ b/tests/T7034.hs
@@ -0,0 +1,11 @@
+main :: IO ()
+main = do
+  print $ r "1E100000"
+  print $ r "1E100000000"
+  print $ r "1E100000000000"
+  print $ r "1E100000000000000"
+  print $ r "1E100000000000000000"
+  print $ r "1E100000000000000000000"
+
+r :: String -> Double
+r = read
diff --git a/tests/T7034.stdout b/tests/T7034.stdout
new file mode 100644
index 0000000..2675153
--- /dev/null
+++ b/tests/T7034.stdout
@@ -0,0 +1,6 @@
+Infinity
+Infinity
+Infinity
+Infinity
+Infinity
+Infinity
diff --git a/tests/all.T b/tests/all.T
index aaa476c..b7a1629 100644
--- a/tests/all.T
+++ b/tests/all.T
@@ -118,4 +118,4 @@ test('4006', if_msys(expect_fail), compile_and_run, [''])
 
 test('5943', normal, compile_and_run, [''])
 test('T5962', normal, compile_and_run, [''])
-
+test('T7034', normal, compile_and_run, [''])