[Qemu-devel] [PATCH v2] rules.mak: Force CFLAGS for all objects in DSO

[Qemu-devel] [PATCH v2] rules.mak: Force CFLAGS for all objects in DSO

[Fam Zheng]

Because of the trick of process-archive-undefs, all .mo objects, even
with --enable-modules, are dependencies of executables.

This breaks CFLAGS propogation because the compiling of module object
will happen too early before building for DSO.

With GCC 5, the linking would fail because .o doesn't have -fPIC. Also,
BUILD_DSO will be missed. (module-common.o will have it, so the stamp
symbol was still liked in .so).

Fix the problem by forcing the CFLAGS on individual .o-cflags during
unnest-vars.

Reported-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Fam Zheng <famz@redhat.com>

---

v2: Simplify as Paolo suggested, while keeping the CFLAGS of
module-common.o
---
 rules.mak | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/rules.mak b/rules.mak
index 3a05627..aec27f8 100644
--- a/rules.mak
+++ b/rules.mak
@@ -102,7 +102,8 @@ endif
 %.o: %.dtrace
 	$(call quiet-command,dtrace -o $@ -G -s $<, "  GEN   $(TARGET_DIR)$@")
 
-%$(DSOSUF): CFLAGS += -fPIC -DBUILD_DSO
+DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO
+module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS)
 %$(DSOSUF): LDFLAGS += $(LDFLAGS_SHARED)
 %$(DSOSUF): %.mo
 	$(call LINK,$^)
@@ -351,6 +352,7 @@ define unnest-vars
         # For non-module build, add -m to -y
         $(if $(CONFIG_MODULES),
              $(foreach o,$($v),
+                   $(eval $($o-objs): CFLAGS += $(DSO_OBJ_CFLAGS))
                    $(eval $o: $($o-objs)))
              $(eval $(patsubst %-m,%-y,$v) += $($v))
              $(eval modules: $($v:%.mo=%$(DSOSUF))),
-- 
2.1.0

Re: [Qemu-devel] [PATCH v2] rules.mak: Force CFLAGS for all objects in DSO

[Andreas Färber]

Am 07.05.2015 um 08:55 schrieb Fam Zheng:
> Because of the trick of process-archive-undefs, all .mo objects, even
> with --enable-modules, are dependencies of executables.
> 
> This breaks CFLAGS propogation because the compiling of module object
> will happen too early before building for DSO.
> 
> With GCC 5, the linking would fail because .o doesn't have -fPIC. Also,
> BUILD_DSO will be missed. (module-common.o will have it, so the stamp
> symbol was still liked in .so).

Did you mean "linked"?

Cheers,
Andreas

> 
> Fix the problem by forcing the CFLAGS on individual .o-cflags during
> unnest-vars.
> 
> Reported-by: Alexander Graf <agraf@suse.de>
> Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> ---
> 
> v2: Simplify as Paolo suggested, while keeping the CFLAGS of
> module-common.o
> ---
>  rules.mak | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/rules.mak b/rules.mak
> index 3a05627..aec27f8 100644
> --- a/rules.mak
> +++ b/rules.mak
> @@ -102,7 +102,8 @@ endif
>  %.o: %.dtrace
>  	$(call quiet-command,dtrace -o $@ -G -s $<, "  GEN   $(TARGET_DIR)$@")
>  
> -%$(DSOSUF): CFLAGS += -fPIC -DBUILD_DSO
> +DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO
> +module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS)
>  %$(DSOSUF): LDFLAGS += $(LDFLAGS_SHARED)
>  %$(DSOSUF): %.mo
>  	$(call LINK,$^)
> @@ -351,6 +352,7 @@ define unnest-vars
>          # For non-module build, add -m to -y
>          $(if $(CONFIG_MODULES),
>               $(foreach o,$($v),
> +                   $(eval $($o-objs): CFLAGS += $(DSO_OBJ_CFLAGS))
>                     $(eval $o: $($o-objs)))
>               $(eval $(patsubst %-m,%-y,$v) += $($v))
>               $(eval modules: $($v:%.mo=%$(DSOSUF))),
> 


-- 
SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Dilip Upmanyu, Graham Norton; HRB
21284 (AG Nürnberg)

Re: [Qemu-devel] [PATCH v2] rules.mak: Force CFLAGS for all objects in DSO

[Fam Zheng]

On Tue, 05/12 00:24, Andreas Färber wrote:
> Am 07.05.2015 um 08:55 schrieb Fam Zheng:
> > Because of the trick of process-archive-undefs, all .mo objects, even
> > with --enable-modules, are dependencies of executables.
> > 
> > This breaks CFLAGS propogation because the compiling of module object
> > will happen too early before building for DSO.
> > 
> > With GCC 5, the linking would fail because .o doesn't have -fPIC. Also,
> > BUILD_DSO will be missed. (module-common.o will have it, so the stamp
> > symbol was still liked in .so).
> 
> Did you mean "linked"?

Yes but it's too late, the commit is already applied to qemu.git :(

Fam

> 
> Cheers,
> Andreas
> 
> > 
> > Fix the problem by forcing the CFLAGS on individual .o-cflags during
> > unnest-vars.
> > 
> > Reported-by: Alexander Graf <agraf@suse.de>
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > 
> > ---
> > 
> > v2: Simplify as Paolo suggested, while keeping the CFLAGS of
> > module-common.o
> > ---
> >  rules.mak | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/rules.mak b/rules.mak
> > index 3a05627..aec27f8 100644
> > --- a/rules.mak
> > +++ b/rules.mak
> > @@ -102,7 +102,8 @@ endif
> >  %.o: %.dtrace
> >  	$(call quiet-command,dtrace -o $@ -G -s $<, "  GEN   $(TARGET_DIR)$@")
> >  
> > -%$(DSOSUF): CFLAGS += -fPIC -DBUILD_DSO
> > +DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO
> > +module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS)
> >  %$(DSOSUF): LDFLAGS += $(LDFLAGS_SHARED)
> >  %$(DSOSUF): %.mo
> >  	$(call LINK,$^)
> > @@ -351,6 +352,7 @@ define unnest-vars
> >          # For non-module build, add -m to -y
> >          $(if $(CONFIG_MODULES),
> >               $(foreach o,$($v),
> > +                   $(eval $($o-objs): CFLAGS += $(DSO_OBJ_CFLAGS))
> >                     $(eval $o: $($o-objs)))
> >               $(eval $(patsubst %-m,%-y,$v) += $($v))
> >               $(eval modules: $($v:%.mo=%$(DSOSUF))),
> > 
> 
> 
> -- 
> SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Felix Imendörffer, Jane Smithard, Dilip Upmanyu, Graham Norton; HRB
> 21284 (AG Nürnberg)
>