RE: Forcing a constructor to be linked

["Dave Korn" <dave dot korn at artimi dot com>]

----Original Message----
>From: Ian Lance Taylor
>Sent: 12 July 2005 03:56

> Darin Johnson writes:
> 
>> I'm running across a linking problem when porting to embedded PowerPC
>> with 
>> GNU tools.  There's a file that was normally linked in because it has a
>> static constructor (and thus a .ctors section), but there are no other
>> external references to that file.  Ie, the static constructor registers
>> a hardware test to a central list that will be run later, and the tests
>> that are included depend upon the libraries included in the build, not
>> upon modifying a source file to add or remove test functions. 
>> 
>> This works fine with GNU ld if the the object file is listed on the
>> command line. However if the file is inside of a library it will not be
>> linked in, even though there's a KEEP() around the .ctors.  Is there an
>> ld option to cause files like this to be linked without having to
>> explicitly create references to them? 
> 
> Not really.  The linker will only bring in files from an archive if
> they are referenced.  Merely having a .ctors section is not a reference.
> 
> You could use --whole-archive, but that is probably not what you are
> after.
> 
> Ian


  The approach we use is to generate a whole load of -u options as part of
the make process that we pass in to ld at final-link time to ensure that
everything from unreferenced .ctor/.dtor sections gets pulled in.  You can
perhaps extract the necessary symbols by using nm on newly-generated .o
files, as part of the makefile rule, and keep them handy somewhere in a
similar way to autogenerated dependency files.



    cheers,
      DaveK
-- 
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