Re: [Xen-devel] [PATCH] mini-os: link to libgcc.a to fix build with gcc7

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jun 30, 2017 at 03:48:41PM +0100, Roger Pau Monné wrote:
> On Fri, Jun 30, 2017 at 03:41:04PM +0100, Wei Liu wrote:
> > CC minios-devel
> > 
> > On Mon, Jun 26, 2017 at 03:28:35PM +0200, Olaf Hering wrote:
> > > gcc7 generates a call to __udivmoddi4 ...
> > > 
> > > stubdom/mini-os-x86_32-grub/mini-os.o: In function `_strtoll_r':
> > > stubdom/newlib-x86_32/i686-xen-elf/newlib/libc/stdlib/../../../../../newlib-1.16.0/newlib/libc/stdlib/strtoll_r.c:110:
> > >  undefined reference to `__udivmoddi4'
> > > make[2]: *** [Makefile:167: stubdom/mini-os-x86_32-grub/mini-os] Error 1
> > > 
> > > ... which the linker only finds if libgcc.a is provided on the 
> > > commandline.
> > > 
> > > Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> > > ---
> > >  Makefile | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/Makefile b/Makefile
> > > index ef8559b..b9c1336 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -162,7 +162,7 @@ $(OBJ_DIR)/arch/x86/minios-x86%.lds:  
> > > arch/x86/minios-x86.lds.S
> > >   $(CPP) $(ASFLAGS) -P $< -o $@
> > >  
> > >  $(OBJ_DIR)/$(TARGET): $(OBJS) $(APP_O) arch_lib 
> > > $(OBJ_DIR)/$(TARGET_ARCH_DIR)/minios-$(MINIOS_TARGET_ARCH).lds
> > > - $(LD) -r $(LDFLAGS) $(HEAD_OBJ) $(APP_O) $(OBJS) $(LDARCHLIB) $(LDLIBS) 
> > > -o $@.o
> > > + $(LD) -r $(LDFLAGS) $(HEAD_OBJ) $(APP_O) $(OBJS) $(LDARCHLIB) $(LDLIBS) 
> > > $$(gcc -print-libgcc-file-name $(CFLAGS)) -o $@.o
> > 
> > Append it to LDLIBS?
> 
> This will break compilation with non-gcc.
> 

I thought about that but mini-os is Linux only? I've tried to build it
on FreeBSD.

If I was wrong, then we should tell gcc to not generate code that relies
on libgcc. That seems impossible by reading the doc...

> Roger.

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