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Date: Thu, 19 Mar 2009 11:31:36 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: under cygwin, zsh cannot run when built against ncurses9-5.7-13
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On Mar 18 07:13, Dave Korn wrote:
>   Ah, gottit.  The bug happens because the libraries are not quite correctly
> constructed.  When you add -lm to the link line, you see this in the map file,
> in the imports section:
> 
> /usr/lib/gcc/i686-pc-cygwin/4.3.2/libgcc_s.dll.a(d000104.o)
> 
> /usr/lib/gcc/i686-pc-cygwin/4.3.2/libgcc_s.dll.a(d000000.o) (cyggcc_s_1_dll_iname)
> /usr/lib/libm.a(d001286.o)    math.o (pow)
> /usr/lib/libm.a(d000000.o)    /usr/lib/libm.a(d001286.o) (_head_libm)
> /usr/lib/libcygwin.a(dll_entry.o)
>                               (_cygwin_dll_entry AT 12)
> 
>   There's no import name chunk for libm (_libm_dll_iname), instead the head
> chunk of the import table in libm.a refers to _cygwin1_dll_iname:
> 
> DKAdmin AT ubik /usr/src/zsh2/zsh-4.3.9/.build/Src/libm
> $ nm ./d000000.o
> 00000000 i .idata$2
> 00000000 i .idata$4
> 00000000 i .idata$5
> 00000000 I __head_libm
>          U _cygwin1_dll_iname
> 
> which means at link time it is resolved by the definition of that symbol
> supplied by libcygwin.a and so the tail chunk from libm is not pulled in to
> correctly 'cap off' the end of the import table.  Then all the name entries
> and IAT table pointers get out of sync and we get confused and overlapping
> import name tables.  Constructing import tables is tricky, and we can't
> optimise away or share any of the .idata$x blocks.
> 
>   There are a number of ways to solve this, either by changing the undefined
> symbol in the head and tail archive members, or maybe by using dlltool or ld
> to generate a fresh import library rather than munging an existing one, but
> I'm going AFK now to get a few hours sleep.

What I'm wondering is, why did it work all these years before?  Is it
a bug in the new binutils?  Or was it a bug in the old binutils to
create working results?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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