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Date: Fri, 20 Mar 2009 22:38:36 -0700 (PDT)
From: "Peter A. Castro" <doctor AT fruitbat DOT org>
To: "A.R. Burgers" <a DOT rburgers AT quicknet DOT nl>
cc: Cygwin List <cygwin AT cygwin DOT com>
Subject: Re: under cygwin, zsh cannot run when built against ncurses9-5.7-13
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On Mon, 16 Mar 2009, A.R. Burgers wrote:

> Any special reason for specifying -lm and -lc when building d3.dll?

Umm...because math functions historically come from lib"m" and the normal
C runtime historically comes from lib"c".  And, anyways, this has always
worked, up 'til now, and there was no notice that these libs should not
be used anymore?

> Without them, pow is mentioned only once in the objdump output. However on 
> 1.5 pow is mentioned only once, even if -lm and -lc
> are specified.

Yes, which means something is likely wrong with the import libs, but what
I'm not sure.

And, from followup email from DaveK it seems he's discovered the import
libs are incorrect in some strange fashion.

> The exact same problem as with zsh, I also run into with fltk's fluid.exe 
> (from current 1.3 svn) on cygwin 1.7 and gcc 3.4.4.
> fltk btw does not link to curses libraries.

Hmm...well, misery loves company :-)

>
> Teun
>
> Peter A. Castro schreef:
>
>> On Sun, 15 Mar 2009, Dave Korn wrote:
>> 
>> Hi Dave!
>> 
>>> Peter A. Castro wrote:
>>>
>>>>   Using the Dependency Walker tool that Chuck pointed out (thanks
>>>> Chuck!)
>>>
>>>  No problem, Basil!
>> 
>> "Basil!"  I love it! (you know I was just kidding! :-)
>> 
>>>> Could this really be a linker problem?
>>>
>>>  If it's not a linker problem, it has to be a faulty import library.  I 
>>> can't
>>> think of any other option that would explain how that import table got 
>>> munged
>>> like that.  I'll see if I can reproduce it.
>> 
>> I've been extracting modules from the import libs and dumping
>> import/export symbols from the two libncurses DLLs, but I can't seem to
>> find anything that looks wrong.
>> 
>> However... this I find strange:
>> 
>> file d3.c:
>> ----------------------------------------------------------------
>> #include <math.h>
>> 
>> double my_pow( double d1, double d2 )
>> {
>>   double d;
>>   d = pow(d1,d2);
>>   return d;
>> }
>> ----------------------------------------------------------------
>> 
>> $ gcc -g -shared -o d3.dll d3.c -lm -lc
>> $ objdump -x d3.dll
>> 
>> ...
>> There is an import table in .idata at 0x10004000
>> 
>> The Import Tables (interpreted .idata section contents)
>>  vma:            Hint    Time      Forward  DLL       First
>>                  Table   Stamp     Chain    Name      Thunk
>>  00004000       00004050 00000000 00000000 0000416c 00004084
>>
>>         DLL Name: cygwin1.dll
>>         vma:  Hint/Ord Member-Name Bound-To
>>         40b8      351  _impure_ptr
>>         40c8      720  calloc
>>         40d4      779  cygwin_detach_dll
>>         40e8      781  cygwin_internal
>>         40fc      802  dll_dllcrt0
>>         410c      917  free
>>         4114     1186  malloc
>>         4120     1395  realloc
>>         412c     1285  pow
>>
>>  00004014       00004070 00000000 00000000 0000416c 000040a4
>>
>>         DLL Name: cygwin1.dll
>>         vma:  Hint/Ord Member-Name Bound-To
>>         412c     1285  pow
>>
>>  00004028       0000407c 00000000 00000000 0000417c 000040b0
>>
>>         DLL Name: KERNEL32.dll
>>         vma:  Hint/Ord Member-Name Bound-To
>>         4134      337  GetModuleHandleA
>>
>>  0000403c       00000000 00000000 00000000 00000000 00000000
>> ...
>> 
>> 
>> Why is 'pow' being pulled in twice?  Maybe it's really the math lib stuff
>> that's tickling the linker?  This is kinda looking more like some linker
>> bug.  Again, I'm not sure where to go next.  It's been a while since I
>> dug into gcc...
>>
>>>    cheers,
>>>      DaveK
>> 
>
>
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-- 
Peter A. Castro <doctor AT fruitbat DOT org> or <Peter DOT Castro AT oracle DOT com>
  	"Cats are just autistic Dogs" -- Dr. Tony Attwood

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