On Wed, Jul 20, 2022 at 9:41 PM Dimitri John Ledkov <dimitri.ledkov@xxxxxxxxxxxxx> wrote: > > Introduce $(GCC) variable with similar semantics to $(LLVM) for > setting path-prefix or version-suffix. > > Currently to correctly and consistently use gcc-10 on Ubuntu 20.04 > LTS, to cross compile a kernel one has to do: > > $ make ... CROSS_COMPILE=riscv64-linux-gnu- \ > CC=riscv64-linux-gnu-gcc-10 \ > HOSTCC=gcc-10 \ > HOSTCXX=g++-10 I think this way is enough. > With this change > > $ make ... CROSS_COMPILE=riscv64-linux-gnu- GCC=-10 > > is sufficient to correctly select a consistent CC/HOSTCC/HOSTCXX set. LLVM=-13 is useful to switch all tools in the LLVM suite such as clang-13, ld.lld-13, llvm-ar-13, etc. When you use GCC, the other tools come from binutils. Also, I tend to think CC and HOSTCC/HOSTCXX are different groups. There is no strong reason for the target GCC and the host GCC must be the same version. You can set CC, HOSTCC, HOSTCXX indivudually. > > Similarly GCC=/path/to/unpacked/toolchains/ can be used to select > toolchain outside of PATH. I think CROSS_COMPILE=/path/to/unpacked/toolchains/ is more common because gcc and binutils are usually bundled together. Overall, I do not think GCC= is so useful. (at least not so useful as LLVM= syntax) > > Update documentation for LLVM variable, and mention that GCC variable > can be used in a similar fashion to set path-prefix, or > version-suffix. > > Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@xxxxxxxxxxxxx> > --- > Documentation/kbuild/kbuild.rst | 12 ++++++++++-- > Makefile | 12 +++++++++--- > tools/testing/selftests/lib.mk | 2 +- > 3 files changed, 20 insertions(+), 6 deletions(-) > > diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst > index ef19b9c13523..6382b082018e 100644 > --- a/Documentation/kbuild/kbuild.rst > +++ b/Documentation/kbuild/kbuild.rst > @@ -276,5 +276,13 @@ whoami and host, respectively. > > LLVM > ---- > -If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead > -of GCC and GNU binutils to build the kernel. > +If this variable is set to 1, Kbuild will use Clang and LLVM utilities > +instead of GCC and GNU binutils to build the kernel. It can also be > +used to set a path prefix, or a version suffix, see "Building > +Linux with Clang/LLVM". > + > +GCC > +--- > +This variable can be used similar to LLVM variable above to set a path > +prefix, or a version suffix for GNU Toolchain binaries. See examples > +in "Building Linux with Clang/LLVM". > diff --git a/Makefile b/Makefile > index 00fd80c5dd6e..e7bd0b572b14 100644 > --- a/Makefile > +++ b/Makefile > @@ -433,8 +433,14 @@ endif > HOSTCC = $(LLVM_PREFIX)clang$(LLVM_SUFFIX) > HOSTCXX = $(LLVM_PREFIX)clang++$(LLVM_SUFFIX) > else > -HOSTCC = gcc > -HOSTCXX = g++ > +ifneq ($(filter %/,$(GCC)),) > +GCC_PREFIX := $(GCC) > +else ifneq ($(filter -%,$(GCC)),) > +GCC_SUFFIX := $(GCC) > +endif > + > +HOSTCC = $(GCC_PREFIX)gcc$(GCC_SUFFIX) > +HOSTCXX = $(GCC_PREFIX)g++$(GCC_SUFFIX) > endif > HOSTPKG_CONFIG = pkg-config > > @@ -461,7 +467,7 @@ OBJDUMP = $(LLVM_PREFIX)llvm-objdump$(LLVM_SUFFIX) > READELF = $(LLVM_PREFIX)llvm-readelf$(LLVM_SUFFIX) > STRIP = $(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX) > else > -CC = $(CROSS_COMPILE)gcc > +CC = $(GCC_PREFIX)$(CROSS_COMPILE)gcc$(GCC_SUFFIX) > LD = $(CROSS_COMPILE)ld > AR = $(CROSS_COMPILE)ar > NM = $(CROSS_COMPILE)nm > diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk > index 1a5cc3cd97ec..777757d54f42 100644 > --- a/tools/testing/selftests/lib.mk > +++ b/tools/testing/selftests/lib.mk > @@ -30,7 +30,7 @@ endif # CROSS_COMPILE > > CC := $(LLVM_PREFIX)clang$(LLVM_SUFFIX) $(CLANG_FLAGS) -fintegrated-as > else > -CC := $(CROSS_COMPILE)gcc > +CC := $(GCC_PREFIX)$(CROSS_COMPILE)gcc$(GCC_SUFFIX) > endif # LLVM > > ifeq (0,$(MAKELEVEL)) > -- > 2.34.1 > -- Best Regards Masahiro Yamada
