| Message ID | 20210309045250.3333311-1-morbo@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [kvm-unit-tests] Makefile: do not use "libgcc" for clang | expand |
Ping. On Mon, Mar 8, 2021 at 8:53 PM Bill Wendling <morbo@google.com> wrote: > > The -nostdlib flag disables the driver from adding libclang_rt.*.a > during linking. Adding a specific library to the command line then > causes the linker to report unresolved symbols, because the libraries > that resolve those symbols aren't automatically added. Turns out clang > doesn't need to specify that library. > > Signed-off-by: Bill Wendling <morbo@google.com> > --- > Makefile | 6 ++++++ > arm/Makefile.common | 2 ++ > x86/Makefile.common | 2 ++ > 3 files changed, 10 insertions(+) > > diff --git a/Makefile b/Makefile > index e0828fe..61a1276 100644 > --- a/Makefile > +++ b/Makefile > @@ -22,10 +22,16 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/ > cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \ > > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;) > > +# cc-name > +# Expands to either gcc or clang > +cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc) > + > #make sure env CFLAGS variable is not used > CFLAGS = > > +ifneq ($(cc-name),clang) > libgcc := $(shell $(CC) --print-libgcc-file-name) > +endif > > libcflat := lib/libcflat.a > cflatobjs := \ > diff --git a/arm/Makefile.common b/arm/Makefile.common > index a123e85..94922aa 100644 > --- a/arm/Makefile.common > +++ b/arm/Makefile.common > @@ -58,7 +58,9 @@ OBJDIRS += lib/arm > libeabi = lib/arm/libeabi.a > eabiobjs = lib/arm/eabi_compat.o > > +ifneq ($(cc-name),clang) > libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name) > +endif > > FLATLIBS = $(libcflat) $(LIBFDT_archive) $(libgcc) $(libeabi) > %.elf: LDFLAGS = -nostdlib $(arch_LDFLAGS) > diff --git a/x86/Makefile.common b/x86/Makefile.common > index 55f7f28..a96b236 100644 > --- a/x86/Makefile.common > +++ b/x86/Makefile.common > @@ -37,7 +37,9 @@ COMMON_CFLAGS += -O1 > # stack.o relies on frame pointers. > KEEP_FRAME_POINTER := y > > +ifneq ($(cc-name),clang) > libgcc := $(shell $(CC) -m$(bits) --print-libgcc-file-name) > +endif > > # We want to keep intermediate file: %.elf and %.o > .PRECIOUS: %.elf %.o > -- > 2.30.1.766.gb4fecdf3b7-goog >
On Mon, Mar 8, 2021 at 8:53 PM Bill Wendling <morbo@google.com> wrote: > > The -nostdlib flag disables the driver from adding libclang_rt.*.a > during linking. Adding a specific library to the command line then > causes the linker to report unresolved symbols, because the libraries > that resolve those symbols aren't automatically added. Turns out clang > doesn't need to specify that library. > > Signed-off-by: Bill Wendling <morbo@google.com> Reviewed-by: Jim Mattson <jmattson@google.com>
On 09/03/21 05:52, Bill Wendling wrote: > The -nostdlib flag disables the driver from adding libclang_rt.*.a > during linking. Adding a specific library to the command line then > causes the linker to report unresolved symbols, because the libraries > that resolve those symbols aren't automatically added. Turns out clang > doesn't need to specify that library. This breaks 32-bit build with clang due to __udivdi3/__umoddi3. Let me post an alternative. Paolo > Signed-off-by: Bill Wendling <morbo@google.com> > --- > Makefile | 6 ++++++ > arm/Makefile.common | 2 ++ > x86/Makefile.common | 2 ++ > 3 files changed, 10 insertions(+) > > diff --git a/Makefile b/Makefile > index e0828fe..61a1276 100644 > --- a/Makefile > +++ b/Makefile > @@ -22,10 +22,16 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/ > cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \ > > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;) > > +# cc-name > +# Expands to either gcc or clang > +cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc) > + > #make sure env CFLAGS variable is not used > CFLAGS = > > +ifneq ($(cc-name),clang) > libgcc := $(shell $(CC) --print-libgcc-file-name) > +endif > > libcflat := lib/libcflat.a > cflatobjs := \ > diff --git a/arm/Makefile.common b/arm/Makefile.common > index a123e85..94922aa 100644 > --- a/arm/Makefile.common > +++ b/arm/Makefile.common > @@ -58,7 +58,9 @@ OBJDIRS += lib/arm > libeabi = lib/arm/libeabi.a > eabiobjs = lib/arm/eabi_compat.o > > +ifneq ($(cc-name),clang) > libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name) > +endif > > FLATLIBS = $(libcflat) $(LIBFDT_archive) $(libgcc) $(libeabi) > %.elf: LDFLAGS = -nostdlib $(arch_LDFLAGS) > diff --git a/x86/Makefile.common b/x86/Makefile.common > index 55f7f28..a96b236 100644 > --- a/x86/Makefile.common > +++ b/x86/Makefile.common > @@ -37,7 +37,9 @@ COMMON_CFLAGS += -O1 > # stack.o relies on frame pointers. > KEEP_FRAME_POINTER := y > > +ifneq ($(cc-name),clang) > libgcc := $(shell $(CC) -m$(bits) --print-libgcc-file-name) > +endif > > # We want to keep intermediate file: %.elf and %.o > .PRECIOUS: %.elf %.o >
diff --git a/Makefile b/Makefile index e0828fe..61a1276 100644 --- a/Makefile +++ b/Makefile @@ -22,10 +22,16 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/ cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \ > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;) +# cc-name +# Expands to either gcc or clang +cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc) + #make sure env CFLAGS variable is not used CFLAGS = +ifneq ($(cc-name),clang) libgcc := $(shell $(CC) --print-libgcc-file-name) +endif libcflat := lib/libcflat.a cflatobjs := \ diff --git a/arm/Makefile.common b/arm/Makefile.common index a123e85..94922aa 100644 --- a/arm/Makefile.common +++ b/arm/Makefile.common @@ -58,7 +58,9 @@ OBJDIRS += lib/arm libeabi = lib/arm/libeabi.a eabiobjs = lib/arm/eabi_compat.o +ifneq ($(cc-name),clang) libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name) +endif FLATLIBS = $(libcflat) $(LIBFDT_archive) $(libgcc) $(libeabi) %.elf: LDFLAGS = -nostdlib $(arch_LDFLAGS) diff --git a/x86/Makefile.common b/x86/Makefile.common index 55f7f28..a96b236 100644 --- a/x86/Makefile.common +++ b/x86/Makefile.common @@ -37,7 +37,9 @@ COMMON_CFLAGS += -O1 # stack.o relies on frame pointers. KEEP_FRAME_POINTER := y +ifneq ($(cc-name),clang) libgcc := $(shell $(CC) -m$(bits) --print-libgcc-file-name) +endif # We want to keep intermediate file: %.elf and %.o .PRECIOUS: %.elf %.o
The -nostdlib flag disables the driver from adding libclang_rt.*.a during linking. Adding a specific library to the command line then causes the linker to report unresolved symbols, because the libraries that resolve those symbols aren't automatically added. Turns out clang doesn't need to specify that library. Signed-off-by: Bill Wendling <morbo@google.com> --- Makefile | 6 ++++++ arm/Makefile.common | 2 ++ x86/Makefile.common | 2 ++ 3 files changed, 10 insertions(+)