Add support to build a host GCC for building the toolchain

A significant amount of users of this project are using it for toolchain
development. These users need to ensure that their code is warning free
before submitting it upstream. Let's support this use case by adding a
configure flag '--enable-host-gcc', which does exactly that:
* build a host GCC before building other components
* setting PATH such that this new GCC is used to build the cross
  toolchain
* enable -Werror for the GCC build

This patch was tested on a Fedora 39 machine (GCC 13),
with the following modification in a GCC source file:
  #if __GNUC__ == 13
  #error Host compiler in use!
  #endif
This fails when building without the new flag and does not fail
when building with latest upstream/master (GCC 14 prerelease).

The '--enable-werror-always' was tested with a warning that showed
up recently in upstream GCC.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

1 files changed, 30 insertions, 10 deletions

diff --git a/Makefile.in b/Makefile.in
index c849d77..daab494 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -119,8 +119,14 @@ MUSL_CC_FOR_TARGET ?= $(MUSL_TUPLE)-gcc
 MUSL_CXX_FOR_TARGET ?= $(MUSL_TUPLE)-g++
 
 CONFIGURE_HOST   = @configure_host@
+PREPARATION_STAMP:=stamps/check-write-permission
 
 all: @default_target@
+ifeq (@enable_host_gcc@,--enable-host-gcc)
+PREPARATION_STAMP+= stamps/install-host-gcc
+PATH := $(builddir)/install-host-gcc/bin:$(PATH)
+GCC_CHECKING_FLAGS := $(GCC_CHECKING_FLAGS) --enable-werror-always
+endif
 newlib: stamps/build-gcc-newlib-stage2
 linux: stamps/build-gcc-linux-stage2
 ifneq (,$(findstring riscv32,$(MUSL_TUPLE)))
@@ -324,11 +330,25 @@ $(srcdir)/%/.git:
 	flock `git rev-parse --git-dir`/config git submodule init $(dir $@) && \
 	flock `git rev-parse --git-dir`/config git submodule update $(dir $@)
 
+stamps/install-host-gcc: $(GCC_SRCDIR) $(GCC_SRC_GIT)
+	if test -f $</contrib/download_prerequisites && test "@NEED_GCC_EXTERNAL_LIBRARIES@" = "true"; then cd $< && ./contrib/download_prerequisites; fi
+	rm -rf $@ $(notdir $@)
+	mkdir $(notdir $@)
+	cd $(notdir $@) && $</configure \
+		--prefix=$(builddir)/install-host-gcc \
+		@with_system_zlib@ \
+		--enable-languages=c,c++ \
+		--disable-bootstrap \
+		--disable-multilib
+	$(MAKE) -C $(notdir $@)
+	$(MAKE) -C $(notdir $@) install
+	mkdir -p $(dir $@) && touch $@
+
 #
 # GLIBC
 #
 
-stamps/build-binutils-linux: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/check-write-permission
+stamps/build-binutils-linux: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 # CC_FOR_TARGET is required for the ld testsuite.
@@ -351,7 +371,7 @@ stamps/build-binutils-linux: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/check
 	$(MAKE) -C $(notdir $@) install
 	mkdir -p $(dir $@) && touch $@
 
-stamps/build-gdb-linux: $(GDB_SRCDIR) $(GDB_SRC_GIT)
+stamps/build-gdb-linux: $(GDB_SRCDIR) $(GDB_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 # CC_FOR_TARGET is required for the ld testsuite.
@@ -498,7 +518,7 @@ stamps/build-gcc-linux-stage2: $(GCC_SRCDIR) $(GCC_SRC_GIT) $(addprefix stamps/b
 	cp -a $(INSTALL_DIR)/$(LINUX_TUPLE)/lib* $(SYSROOT)
 	mkdir -p $(dir $@) && touch $@
 
-stamps/build-binutils-linux-native: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/build-gcc-linux-stage2 stamps/check-write-permission
+stamps/build-binutils-linux-native: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/build-gcc-linux-stage2 $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 	cd $(notdir $@) && $</configure \
@@ -555,7 +575,7 @@ stamps/build-gcc-linux-native: $(GCC_SRCDIR) $(GCC_SRC_GIT) stamps/build-gcc-lin
 # NEWLIB
 #
 
-stamps/build-binutils-newlib: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/check-write-permission
+stamps/build-binutils-newlib: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 # CC_FOR_TARGET is required for the ld testsuite.
@@ -575,7 +595,7 @@ stamps/build-binutils-newlib: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/chec
 	$(MAKE) -C $(notdir $@) install
 	mkdir -p $(dir $@) && touch $@
 
-stamps/build-gdb-newlib: $(GDB_SRCDIR) $(GDB_SRC_GIT)
+stamps/build-gdb-newlib: $(GDB_SRCDIR) $(GDB_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 # CC_FOR_TARGET is required for the ld testsuite.
@@ -741,7 +761,7 @@ stamps/build-gcc-newlib-stage2: $(GCC_SRCDIR) $(GCC_SRC_GIT) stamps/build-newlib
 # MUSL
 #
 
-stamps/build-binutils-musl: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) stamps/check-write-permission
+stamps/build-binutils-musl: $(BINUTILS_SRCDIR) $(BINUTILS_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 # CC_FOR_TARGET is required for the ld testsuite.
@@ -870,7 +890,7 @@ stamps/build-gcc-musl-stage2: $(GCC_SRCDIR) $(GCC_SRC_GIT) stamps/build-musl-lin
 	cp -a $(INSTALL_DIR)/$(MUSL_TUPLE)/lib* $(SYSROOT)
 	mkdir -p $(dir $@) && touch $@
 
-stamps/build-spike: $(SPIKE_SRCDIR) $(SPIKE_SRC_GIT)
+stamps/build-spike: $(SPIKE_SRCDIR) $(SPIKE_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 	cd $(notdir $@) && $</configure \
@@ -906,7 +926,7 @@ stamps/build-pk64: $(PK_SRCDIR) $(PK_SRC_GIT) stamps/build-gcc-newlib-stage2
 	mkdir -p $(dir $@)
 	date > $@
 
-stamps/build-qemu: $(QEMU_SRCDIR) $(QEMU_SRC_GIT)
+stamps/build-qemu: $(QEMU_SRCDIR) $(QEMU_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 	cd $(notdir $@) && $</configure \
@@ -971,7 +991,7 @@ stamps/build-llvm-newlib: $(LLVM_SRCDIR) $(LLVM_SRC_GIT) stamps/build-gcc-newlib
 	    ln -s -f clang++ $(NEWLIB_TUPLE)-clang++
 	mkdir -p $(dir $@) && touch $@
 
-stamps/build-dejagnu: $(DEJAGNU_SRCDIR) $(DEJAGNU_SRC_GIT)
+stamps/build-dejagnu: $(DEJAGNU_SRCDIR) $(DEJAGNU_SRC_GIT) $(PREPARATION_STAMP)
 	rm -rf $@ $(notdir $@)
 	mkdir $(notdir $@)
 	cd $(notdir $@) && $</configure \
@@ -1101,7 +1121,7 @@ report-binutils-linux: stamps/check-binutils-linux
 	    `find build-binutils-linux/ -name *.sum |paste -sd "," -`
 
 clean:
-	rm -rf build-* stamps install-newlib-nano
+	rm -rf build-* install-* stamps install-newlib-nano
 
 .PHONY: report-gdb-newlib report-gdb-newlib-nano
 report-gdb-newlib: stamps/check-gdb-newlib