Understanding the undefine flags passed to gcc when linking
simonmarhaskell at gmail.com
Thu Mar 13 16:47:07 EDT 2008
Bruce, Joseph R (Joe) wrote:
> Thanks Simon. That is the best answer I've received to this question in
> many askings.
> I will try to go the shared library route.
Shared libraries are currently experimental - you'll probably experience
problems, and parts of the infrastructure are still in flux. I wouldn't
recommend relying on shared libraries just yet.
> A question about you last
> comment: when you say link RTS and base, you mean extract the object
> files and package in a single .a? Am I going to run into namespace
Yes, put the whole of the RTS and base into a single .a. You shouldn't
run into namespace collisions, as the symbol namespace is global anyway.
>> -----Original Message-----
>> From: Simon Marlow [mailto:simonmarhaskell at gmail.com]
>> Sent: Wednesday, March 12, 2008 3:18 PM
>> To: Bruce, Joseph R (Joe)
>> Cc: glasgow-haskell-users at haskell.org
>> Subject: Re: Understanding the undefine flags passed to gcc
>> when linking
>> Bruce, Joseph R (Joe) wrote:
>>> When I run 'ghc -v ...', the linking is done via gcc->ld
>> with a large
>>> list of -u flags passed in. I'm hoping to find a way to link my
>>> object files without those flags, but first I need to
>> understand what
>>> they are doing. Can someone explain it to me? Or point me to
>>> documentation that explains it?
>>> My ultimate goal is to build a static Haskell library and make it
>>> available to c programmers ignorant of Haskell. The undefines
>>> described above are a major obstacle. Does anyone know a
>> way around them?
>> The -u flags arise because there is a circular dependency
>> between the RTS (libHSrts.a) and the base package
>> (libHSbase.a). The RTS refers to a few datatypes and
>> functions in the base package, for instance the constructors
>> for True and False, I#, C# and so on, and some exceptions
>> that the RTS automatically raises for certain events (e.g.
>> stack overflow, non-termination).
>> One way to avoid needing the -u flags would be to link the
>> base package twice, but that would slow down linking, and
>> twice might not be enough.
>> With shared libraries there's no problem, because we always
>> just link the whole library, this is only an issue with
>> static libraries.
>> So for building a static Haskell library, can't you just link
>> the RTS and base package together in a single .a file?
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