#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
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Comment(by gwright):
Replying to [comment:18 simonmar]:
> Looks like you're getting closer to nailing this one. If you turn on
linker debugging (`+RTS -Dl`) you should be able to see it resolving the
relocation at that address, and that should give you enough information to
map it to a source file. Once you have the source file, you can look at
the assembly and see what the relocation is supposed to be doing.
Yes, turning on linker debugging is the plan. I've needed to add some
additional debug statements to find out what happens to the `__const`
section of the `__TEXT` segment. This is supposed to be non-relocatable
static data, which by my reading of the documentation means loaded at a
specified offset from the `__text` section. One of two things is
happening: in the statement that loads `$xmm7`,
{{{
movsd 0x281b7c(%rip),%xmm7
}}}
either the offset from the instruction pointer is wrong, or the expected
data isn't at that location. In the saved assembly files, I've found a
number of places where `(-<double>)` is computed, and the sign bit mask
seems always stored in the `__const` section of `__TEXT`. If the data's
in the wrong place, I'm guessing either an alignment bug or something
really odd that puts it in the wrong section.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4867#comment:19>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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