[dmd-internals] "Previous Definition Different" w/ array ops

[David Simcha]

Never mind, I got it.  http://d.puremagic.com/issues/show_bug.cgi?id=5592
The thing that made it hard to reproduce was that I was using the wrong
array op.  What the heck is the difference between
__arrayExpSliceMulSliceAddass_d and
__arraySliceExpMulSliceAddass_d anyhow?  From what I can tell, which one
gets called depends on the order you write your array op in.  arr1[] += num
* arr2[] calls __arrayExpSliceMulSliceAddass_d and arr1[] += arr2[] * num
calls __arraySliceExpMulSliceAddass_d .  Isn't multiplication commutative
even in inexact floating point arithmetic?  Why two functions?

On Tue, Feb 15, 2011 at 12:07 PM, Jason House
<jason.james.house at gmail.com>wrote:

> The complete linker error with mangled symbol name and the candidate code
> generating the symbol in the first place is probably enough. At one point, I
> posted an error message, and Don was able to infer everything else without
> seeing a line of my code. That might not be the case here, but it's probably
> the bulk of the needed info.
>
> Sent from my iPhone
>
> On Feb 15, 2011, at 11:33 AM, David Simcha <dsimcha at gmail.com> wrote:
>
> > Whenever I use array ops in multi-module projects, I always seem to run
> into "Previous definition different" linker errors.  This seems to occur
> when I call the same array op using library function from multiple modules
> in the same project.  Moving things around to different modules and
> recompiling always seems to solve them at the expense of uglifying my code.
>  Unfortunately, this is one of those frustrating bugs that only seems to
> occur on real-world code, i.e. code that has multiple modules, lots of
> indirection, libraries, etc.  I can't for the life of me come up with a
> reduced test case.
> >
> > Has anyone else been experiencing similar issues?  Alternatively, can
> someone with a better mental model of how things work at the binary level
> please suggest how this bug might be reproduced in a test case that's less
> than 20 thousand lines of code?  (I find linker bugs very difficult to
> isolate and file bug reports on because I have no mental model of how things
> work at that low a level.  My mental model basically only goes down to
> assembly language, not the process of turning a pile of assembly language
> files into a working executable or shared library.)
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