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	Sat, 09 May 2020 09:48:34 -0700 (PDT)
Subject:	Re: Changes to config/i386/djgpp.c
To:	djgpp AT delorie DOT com
References:	<65c420b7-835c-cba6-6ff6-22d530d513bf AT iki DOT fi>
	<c1091957-2c67-68ae-4614-2c6fbded7580 AT gmail DOT com>
	<b39f4c27-15bf-d773-db70-94d307f87de3 AT iki DOT fi>
Cc:	andris DOT pavenis AT iki DOT fi
From:	"J.W. Jagersma (jwjagersma AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
Message-ID:	<11a24e98-68c6-bf28-87da-e1fadcefefef@gmail.com>
Date:	Sat, 9 May 2020 18:48:33 +0200
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On 2020-05-09 18:28, Andris Pavenis (andris DOT pavenis AT iki DOT fi) [via djgpp AT delorie DOT com] wrote:
> On 5/9/20 4:55 PM, J.W. Jagersma wrote:
>> Hi Andris,
>> Thanks for making gcc 10 available so quickly.  I updated my build
>> scripts and applied my patch, but then ran into a problem:
>>
>>      i386-pc-msdosdjgpp-gcc -pipe ... -c symify.c
>>      i386-pc-msdosdjgpp-ld -s  ../../../lib/crt0.o symify.o ../../../lib/libdbg.a ../../../lib/libc.a -o ../../../bin/symify.exe D:/msys64/usr/local/cross/lib/gcc/i386-pc-msdosdjgpp/10.1.0/libgcc.a -T ../../../lib/djgpp.djl
>>      D:\msys64\usr\local\cross\bin\i386-pc-msdosdjgpp-ld.exe: ../../../lib/libc.a(stdiohk.o):stdiohk.c:(.data+0x0): multiple definition of `__stdio_cleanup_hook'; ../../../lib/libc.a(exit.o):exit.c:(.bss+0x8): first defined here
>>      make[2]: *** [makefile:22: ../../../bin/symify.exe] Error 1
>>      make[1]: *** [makefile.sub:2: all_subs] Error 2
>>      make: *** [makefile:10: all] Error 2
>>
>> At first I thought it was caused by my patch, since it looks like this
>> symbol is placed in .bss in one compilation unit, and .data in another.
>> However this problem didn't occur with gcc 9.  Inspecting the release
>> notes for gcc 10, I found that gcc now links with -fno-common by
>> default, so I think this needs to be fixed in libc now by declaring the
>> symbol in exit.c with extern linkage:
>>
>>      extern void (*__stdio_cleanup_hook)(void);
>>
>> Or alternatively, libc needs to be compiled with -fcommon now.
>> Did you run into this issue too?  How did you solve it?
> 
> Known problem:
> 
> int foo;
> 
> int foo = 1;
> 
> No more works with gcc-10. One must write instead:
> 
> extern int foo;
> 
> int foo = 1;
> 
> Example how it can be fixed can be seen in ArchLinux AUR package which I updated yesterday:
> 
> https://aur.archlinux.org/packages/djgpp-djcrx/
> 
> Problem is mentioned in https://gcc.gnu.org/gcc-10/changes.html
> 
> The changes done for AUR package should perhaps be not committed to DJGPP CVS (no need to support old compilers for ArchLinux)
> 
> Andris
> 
> 
> PS. Sending also to djgpp mailing list as somebody else could be interested in that

Thanks, I figured out a solution already:

https://github.com/jwt27/djgpp-cvs/commit/9fcd924b8eec562eeacf53c92a18e06aacb48fa9.patch

I think this is safe to commit to cvs, the -fcommon option is already
mentioned in the manual for gcc 2.95.3, so it should be compatible even
with ancient compiler versions.

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