Re: NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Christian Franke <Christian.Franke@t-online.de>]

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Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> Christian Franke wrote:
>    
>
>> The *_frame_info symbols are set undefined to force linkage of the
>> libgcc_s shared library or dll.
>>
>> This can be prevented by TARGET_LDFLAGS=-static-libgcc. To build from
>> grub-1.98 tarball on Cygwin, run configure with this argument.
>>
>> May also be necessary on other build platforms when -shared-libgcc is
>> the default. It may be possible simply set -static-libgcc
>> unconditionally.
>>
>>      
> We already supply -lgcc --static-libgcc. Do you know why it still had
> issues?
>    

The above is only set when linking the kernel image.

According to 'gcc -dumpspecs' of Cygwin gcc 4.3.4-3, options '-u 
___[de]register_frame_info' are always passed to the linker if 
-static-libgcc is not specified. This is Cygwin and MinGW specific: In 
the exe startup code these symbols are loaded only if present, so the 
DLL must be forced to load first.

As a consequence, the symbols are also set undefined when the GRUB 
pre-*.o files are generated with 'ld -r'.

The attached patch works for me with the bzr revision preceding the 
NEED_REGISTER_FRAME_INFO fix.


> And I also doubt usefullness of pulling these functions since reference
> to them is purely dummy: no relocation uses it so it will only increase
> code size. Another concern is the behviour of these functions in grub
> environment if they ever get called.
>
>    

AFAICS from the gcc source, the functions are used in EH stack unwinding 
code in libgcc. The compiler itself does not generate calls to these 
functions.


-- 
Regards,
Christian Franke


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=== modified file 'Makefile.in'
--- Makefile.in	2010-04-10 23:14:31 +0000
+++ Makefile.in	2010-04-14 08:04:34 +0000
@@ -98,12 +98,12 @@
 OBJCONV = @OBJCONV@
 TARGET_CPPFLAGS = @TARGET_CPPFLAGS@ -I$(srcdir)/include -I$(builddir) -I$(builddir)/include \
 	-Wall -W
-TARGET_LDFLAGS = -nostdlib @TARGET_LDFLAGS@
+TARGET_LDFLAGS = -nostdlib -static-libgcc @TARGET_LDFLAGS@
 TARGET_IMG_LDSCRIPT = @TARGET_IMG_LDSCRIPT@
 TARGET_IMG_LDFLAGS = -nostdlib @TARGET_IMG_LDFLAGS@
 TARGET_IMG_CFLAGS = @TARGET_IMG_CFLAGS@
 TARGET_OBJ2ELF = @TARGET_OBJ2ELF@
-kernel_img_LDFLAGS = -static-libgcc -lgcc
+kernel_img_LDFLAGS = -lgcc
 EXEEXT = @EXEEXT@
 OBJCOPY = @OBJCOPY@
 STRIP = @STRIP@