#4867: ghci displays negative floats incorrectly (was: Incorrect result from
trig
functions)
-------------------------------+--------------------------------------------
Reporter: gwright | Owner: gwright
Type: bug | Status: new
Priority: high | Milestone: 7.0.2
Component: GHCi | Version: 7.0.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: MacOS X | Blocking:
Architecture: x86_64 (amd64) | Failure: Incorrect result at runtime
-------------------------------+--------------------------------------------
Comment(by gwright):
Something strange is still going on. With the test program
{{{
gwright-macbook> cat foo.hs
--
-- Test returning -1.0
--
module Main where
main = print (-1.0 :: Double)
}}}
on HEAD I get
{{{
gwright-macbook> inplace/bin/ghc-stage2 --interactive foo.hs
GHCi, version 7.1.20110210: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
[1 of 1] Compiling Main ( foo.hs, interpreted )
Ok, modules loaded: Main.
*Main> main
--1.0
*Main>
}}}
Compiling the same program gives
{{{
gwright-macbook> inplace/bin/ghc-stage2 --make foo.hs
[1 of 1] Compiling Main ( foo.hs, foo.o )
Linking foo ...
ld: warning: -read_only_relocs cannot be used with x86_64
gwright-macbook> ./foo
-1.0
gwright-macbook>
}}}
So this appears to be a `ghci` or linker bug still.
Slightly more distressing is when I tried the above test program on the
ghc-7.0 tree that I did most of my debugging work on:
{{{
gwright-macbook> inplace/bin/ghc-stage2 --interactive foo.hs
GHCi, version 7.0.1.20101221: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
Ok, modules loaded: Main.
Prelude Main> main
--0.0
Prelude Main>
}}}
in this case the answer is entirely wrong.
I went back to `gdb` and stepped through my original test program until I
reached the location where `%xmm7` is loaded. The memory contents pointed
to by `%rip` plus the offset seem to contain the correct mask, but I will
check again.
I suspect an off by one or size of the relocated object issue.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4867#comment:33>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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