Which of two functions gets linked?

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8 total messages Started by Mark Taylor Mon, 12 Jul 2004 21:16

#528

Author: Mark Taylor
Date: Mon, 12 Jul 2004 21:16

9 lines
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Hi all,

When an identical function is defined in a .lib file and in a .c file, 
is there a way to control which one is linked in by the PowerPC Mach-O 
linker?  It seems to be random and uncontrollable, but perhaps I am 
missing something?

Thanks very much,
- Mark Taylor

Re: Which of two functions gets linked?

#530

Author: MW Ron
Date: Tue, 13 Jul 2004 18:42

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In article <user02.20.mdt-0ED944.16165012072004@corp.supernews.com>,
 Mark Taylor <user02.20.mdt@spamgourmet.com> wrote:

>Hi all,
>
>When an identical function is defined in a .lib file and in a .c file, 
>is there a way to control which one is linked in by the PowerPC Mach-O 
>linker?  It seems to be random and uncontrollable, but perhaps I am 
>missing something?

The source file should ALWAYS be used before the library even if the 
link order is different are you seeing something other than that?

Ron

-- 
Metrowerks Community Forum is a free online resource for developers 
to discuss CodeWarrior topics with other users and Metrowerks' staff
        --   http://www.metrowerks.com/community  --

 Ron Liechty - MWRon@metrowerks.com - http://www.metrowerks.com

Re: Which of two functions gets linked?

#531

Author: Mark Taylor
Date: Tue, 13 Jul 2004 19:43

29 lines
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In article <mwron-4EF244.14421113072004@news.newsguy.com>,
 MW Ron <mwron@metrowerks.com> wrote:

> In article <user02.20.mdt-0ED944.16165012072004@corp.supernews.com>,
>  Mark Taylor <user02.20.mdt@spamgourmet.com> wrote:
> 
> >Hi all,
> >
> >When an identical function is defined in a .lib file and in a .c file, 
> >is there a way to control which one is linked in by the PowerPC Mach-O 
> >linker?  It seems to be random and uncontrollable, but perhaps I am 
> >missing something?
> 
> The source file should ALWAYS be used before the library even if the 
> link order is different are you seeing something other than that?
> 
> Ron

No, in fact the library function was being used and the linker was dead 
stripping the function in the .c file.  The desired behavior is for the 
.c function to override the library version.

I took Adriaan's advice and I checked the link order list.  It turned 
out that the .c file was the last item in the list since it was recently 
added to the project.  Moving it ahead of the libraries fixed the 
problem.  (Thanks, Adriaan!)  Upon reading your message I take it that 
it should not work this way?

- Mark

Re: Which of two functions gets linked?

#532

Author: Miro Jurisic
Date: Tue, 13 Jul 2004 20:57

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In article <user02.20.mdt-D089B9.14432713072004@corp.supernews.com>,
 Mark Taylor <user02.20.mdt@spamgourmet.com> wrote:

> I took Adriaan's advice and I checked the link order list.  It turned 
> out that the .c file was the last item in the list since it was recently 
> added to the project.  Moving it ahead of the libraries fixed the 
> problem.  (Thanks, Adriaan!)  Upon reading your message I take it that 
> it should not work this way?

AFAIK Ron is confused. There used to be a time when source files always trumped 
libraries, but that is no longer the case.

meeroh

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Re: Which of two functions gets linked?

#533

Author: MW Ron
Date: Tue, 13 Jul 2004 21:27

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In article <macdev-CCB0C5.16570413072004@senator-bedfellow.mit.edu>,
 Miro Jurisic <macdev@meeroh.org> wrote:

>> I took Adriaan's advice and I checked the link order list.  It turned 
>> out that the .c file was the last item in the list since it was recently 
>> added to the project.  Moving it ahead of the libraries fixed the 
>> problem.  (Thanks, Adriaan!)  Upon reading your message I take it that 
>> it should not work this way?
>
>AFAIK Ron is confused. There used to be a time when source files always 
>trumped 
>libraries, but that is no longer the case.

As far as I know I'm confused too :),   however,  I'll assume that this 
behavior has changed and submit it as a bug report, as I don't think 
that is the desired behavior.

Ron

-- 
Metrowerks Community Forum is a free online resource for developers 
to discuss CodeWarrior topics with other users and Metrowerks' staff
        --   http://www.metrowerks.com/community  --

 Ron Liechty - MWRon@metrowerks.com - http://www.metrowerks.com

Re: Which of two functions gets linked?

#534

Author: Ed Swartz
Date: Tue, 13 Jul 2004 22:03

14 lines
1873 bytes

> >
> >AFAIK Ron is confused. There used to be a time when source files always
> >trumped
> >libraries, but that is no longer the case.
>
> As far as I know I'm confused too :),   however,  I'll assume that this
> behavior has changed and submit it as a bug report, as I don't think
> that is the desired behavior.

I'm confused too.  Ron's explanation matches the Win32 and all Codewarrior
ELF linkers, but it seems the Mach-O linker is using this alternate
ordering.

-- Ed

Re: Which of two functions gets linked?

#535

Author: MW Ron
Date: Wed, 14 Jul 2004 16:12

39 lines
2554 bytes

In article <user02.20.mdt-0ED944.16165012072004@corp.supernews.com>,
 Mark Taylor <user02.20.mdt@spamgourmet.com> wrote:

>When an identical function is defined in a .lib file and in a .c file, 
>is there a way to control which one is linked in by the PowerPC Mach-O 
>linker?  It seems to be random and uncontrollable, but perhaps I am 
>missing something?

The linker builds 3 list of files:

   files ending in ".o" (if 'Enforce link order for ".o" files' is off)
   files which the IDE associates with a text file (sources)
   all other files (dylibs, and libs)

The ".o" case only exists in Mach-O but the rest of the code is the same 
for both PEF and our Mach-O linker. This ".o" handling is important 
since crt1.o needs to be treated as if it was first, and our users were 
not very careful about doing this so we by default put all ".o" files 
first, if the user enables Enforce link order for ".o" files then they 
have to make sure that crt1.o appears in the correct link order.

The 3 lists are merge together into a single list in the order of the 
list above. The linker then walks that list in that order, the only 
special case is dylibs appear in order but are not actually processed 
until the frameworks are scanned.

If you know of any other situation then we would like a bug report on 
this.

Ron

-- 
Metrowerks Community Forum is a free online resource for developers 
to discuss CodeWarrior topics with other users and Metrowerks' staff
        --   http://www.metrowerks.com/community  --

 Ron Liechty - MWRon@metrowerks.com - http://www.metrowerks.com

Re: Which of two functions gets linked?

#536

Author: MW Ron
Date: Wed, 14 Jul 2004 16:16

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In article <macdev-CCB0C5.16570413072004@senator-bedfellow.mit.edu>,
 Miro Jurisic <macdev@meeroh.org> wrote:

>AFAIK Ron is confused. There used to be a time when source files always 
>trumped 
>libraries, but that is no longer the case.

not to be redundant,  but in case you missed the earlier posting because 
I posted out of order...

.o files trump source files,  Source files trump  .lib files ,  DLLs are 
processed when frameworks are scanned.

Ron

-- 
Metrowerks Community Forum is a free online resource for developers 
to discuss CodeWarrior topics with other users and Metrowerks' staff
        --   http://www.metrowerks.com/community  --

 Ron Liechty - MWRon@metrowerks.com - http://www.metrowerks.com

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