[Tcl-bugs] [ tcl-Bugs-2959713 ] Link error with gcc 4.1

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Bugs item #2959713, was opened at 2010-02-26 11:25
Message generated for change (Comment added) made by kennykb
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Category: 53. Configuration and Build Tools
Group: development: 8.6b1.1
Status: Open
Resolution: None
Priority: 7
Private: No
Submitted By: Decoster Jos (decosterjos)
>Assigned to: Jan Nijtmans (nijtmans)
Summary: Link error with gcc 4.1

Initial Comment:
Building Tcl from CVS head with gcc 4.1 results in the following link error:

/usr/bin/ld: tclTomMathInterface.o: relocation R_X86_64_PC32 against symbol `tclTomMathConstStubs' can not be used when making a shared object; recompile with -fPIC

Adding MODULE_SCOPE to tclStubInit.c as suggested by Kevin Kenny:

MODULE_SCOPE const TclTomMathStubs tclTomMathConstStubs = {
   ..

solves the issue..

Jos.

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>Comment By: Kevin B KENNY (kennykb)
Date: 2010-02-27 10:59

Message:
Assigning to nijtmans - Jeff, why'd you assign it back to me?

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Comment By: Jeffrey Hobbs (hobbs)
Date: 2010-02-26 17:27

Message:
Kevin's patch is correct, except the real question is why these aren't all
static.  It would need one modification to remove the existing
"MODULE_SCOPE" for tclStubs in tclStubInit.c:44.  Also, tclOOStubs needs
the treatment.

Jan - can you please explain why these aren't all being left static?

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Comment By: Kevin B KENNY (kennykb)
Date: 2010-02-26 12:04

Message:
In gcc 4.1, it is not valid to initialise a data item with a pointer to an
exported data item. (It is all right to use a pointer to an exported
function or a pointer to a data item at module or static scope.) The
problem can be worked around by using -Wl,-Bsymbolic on the link flags, but
that approach should not be adopted without further thought: see
http://software.intel.com/en-us/articles/performance-tools-for-software-developers-bsymbolic-can-cause-dangerous-side-effects/
for some of the pitfalls. Alternatively, the scope of the Stubs tables can
be restricted: the attached patch to tools/genStubs.tcl puls it back to
MODULE_SCOPE.

Donal Fellows and I discussed the correct linkage for tclTomMathStubs and
tclOOStubs, and we believe that both of those tables ought to be 'static'
unless there's something that you need to do with them that we fail to
comprehend. In any case, I don't understand what you're trying to do with
the code that marks them 'static' if they have subinterfaces and 'extern'
otherwise. In any case, 'extern' is wrong: all symbols exported from the
shared library should be EXTERN, and all symbols internal to it should be
MODULE_SCOPE.

The attached patch attempts to be conservative: it makes the sharing as
wide as possible while still linking successfully. I'd also request that
you add some commentary in genStubs.tcl giving the rest of us some
indication what you're trying to do. The change to make the tables external
rather than static seems somewhat gratuitous, and of course has been
observed to break at least one build.

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Comment By: Kevin B KENNY (kennykb)
Date: 2010-02-26 11:29

Message:
I'm looking into this - it relates to nijtmans's commit to
tools/genStubs.tcl on 2010-02-05.


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