Re: Support for out-of-tree build

[Petr Hosek <phosek@chromium.org>]

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Attached is an update version which doesn't use VPATH and supports both
in-tree and out-of-tree builds.

One way to improve this even further would be to completely avoid the
mkasmdep and instead include the architecture specific object files into
the list of objects directly (filtering out the generic versions). Would
that be a preferred way?

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From 1336bc5c1eddc43214559712f85702efba8aa864 Mon Sep 17 00:00:00 2001
From: Petr Hosek <phosek@chromium.org>
Date: Thu, 5 Nov 2015 14:51:50 -0800
Subject: [PATCH] suport out-of-tree build

this change add support for building musl outside of the source
tree. the implementation is similar to autotools where running
configure in a different folder creates config.mak in the current
working directory and symlinks the makefile, which contains the
logic for creating all necessary directories and resolving paths
relative to the source directory. based on patch by Szabolcs Nagy.
---
 Makefile  | 93 +++++++++++++++++++++++++++++++++++++++++----------------------
 configure | 24 ++++++++++++++---
 2 files changed, 82 insertions(+), 35 deletions(-)

diff --git a/Makefile b/Makefile
index 2b21015..a022411 100644
--- a/Makefile
+++ b/Makefile
@@ -8,6 +8,7 @@
 # Do not make changes here.
 #
 
+srcdir = .
 exec_prefix = /usr/local
 bindir = $(exec_prefix)/bin
 
@@ -16,12 +17,24 @@ includedir = $(prefix)/include
 libdir = $(prefix)/lib
 syslibdir = /lib
 
-SRCS = $(sort $(wildcard src/*/*.c arch/$(ARCH)/src/*.c))
-OBJS = $(SRCS:.c=.o)
+SRCS = $(sort $(wildcard $(srcdir)/src/*/*.c $(srcdir)/arch/$(ARCH)/src/*.c))
+OBJS = $(SRCS:$(srcdir)/%.c=%.o)
 LOBJS = $(OBJS:.o=.lo)
 GENH = include/bits/alltypes.h
 GENH_INT = src/internal/version.h
-IMPH = src/internal/stdio_impl.h src/internal/pthread_impl.h src/internal/libc.h
+IMPH = $(addprefix $(srcdir)/, src/internal/stdio_impl.h src/internal/pthread_impl.h src/internal/libc.h)
+
+SRCS_SUB = $(wildcard $(srcdir)/src/*/$(ARCH)$(ASMSUBARCH)/*.sub)
+OBJS_SUB = $(foreach s,$(SRCS_SUB),$(dir $(patsubst $(srcdir)/%/,%,$(dir $(s))))$(notdir $(s:.sub=.o)))
+LOBJS_SUB = $(OBJS_SUB:.o=.lo)
+
+SRCS_S = $(wildcard $(srcdir)/src/*/$(ARCH)*/*.s)
+OBJS_S = $(foreach s,$(SRCS_S),$(dir $(patsubst $(srcdir)/%/,%,$(dir $(s))))$(notdir $(s:.s=.o)))
+LOBJS_S = $(OBJS_S:.o=.lo)
+
+OBJS_C = $(filter-out $(OBJS_S) $(OBJS_SUB), $(OBJS))
+LOBJS_C = $(OBJS_C:.o=.lo)
+OBJS_C += crt/crt1.o crt/Scrt1.o crt/rcrt1.o crt/crti.o crt/crtn.o
 
 LDFLAGS =
 LDFLAGS_AUTO =
@@ -32,7 +45,7 @@ CFLAGS_AUTO = -Os -pipe
 CFLAGS_C99FSE = -std=c99 -ffreestanding -nostdinc 
 
 CFLAGS_ALL = $(CFLAGS_C99FSE)
-CFLAGS_ALL += -D_XOPEN_SOURCE=700 -I./arch/$(ARCH) -I./src/internal -I./include
+CFLAGS_ALL += -D_XOPEN_SOURCE=700 -I$(srcdir)/arch/$(ARCH) $(sort -I./src/internal -I$(srcdir)/src/internal) $(sort -I./include -I$(srcdir)/include)
 CFLAGS_ALL += $(CPPFLAGS) $(CFLAGS_AUTO) $(CFLAGS)
 CFLAGS_ALL_STATIC = $(CFLAGS_ALL)
 CFLAGS_ALL_SHARED = $(CFLAGS_ALL) -fPIC -DSHARED
@@ -41,10 +54,11 @@ LDFLAGS_ALL = $(LDFLAGS_AUTO) $(LDFLAGS)
 
 AR      = $(CROSS_COMPILE)ar
 RANLIB  = $(CROSS_COMPILE)ranlib
-INSTALL = ./tools/install.sh
+INSTALL = $(srcdir)/tools/install.sh
 
-ARCH_INCLUDES = $(wildcard arch/$(ARCH)/bits/*.h)
-ALL_INCLUDES = $(sort $(wildcard include/*.h include/*/*.h) $(GENH) $(ARCH_INCLUDES:arch/$(ARCH)/%=include/%))
+ARCH_INCLUDES = $(wildcard $(srcdir)/arch/$(ARCH)/bits/*.h)
+INCLUDES = $(wildcard $(srcdir)/include/*.h $(srcdir)/include/*/*.h)
+ALL_INCLUDES = $(sort $(INCLUDES:$(srcdir)/%=%) $(GENH) $(ARCH_INCLUDES:$(srcdir)/arch/$(ARCH)/%=include/%))
 
 EMPTY_LIB_NAMES = m rt pthread crypt util xnet resolv dl
 EMPTY_LIBS = $(EMPTY_LIB_NAMES:%=lib/lib%.a)
@@ -55,6 +69,8 @@ TOOL_LIBS = lib/musl-gcc.specs
 ALL_LIBS = $(CRT_LIBS) $(STATIC_LIBS) $(SHARED_LIBS) $(EMPTY_LIBS) $(TOOL_LIBS)
 ALL_TOOLS = tools/musl-gcc
 
+SRC_DIRS = $(sort $(dir $(OBJS) $(ALL_LIBS) $(ALL_TOOLS)) arch/$(ARCH)/bits/ crt/ include/ src/internal/)
+
 WRAPCC_GCC = gcc
 WRAPCC_CLANG = clang
 
@@ -64,6 +80,17 @@ LDSO_PATHNAME = $(syslibdir)/ld-musl-$(ARCH)$(SUBARCH).so.1
 
 all: $(ALL_LIBS) $(ALL_TOOLS)
 
+$(ALL_LIBS): | lib/
+$(ALL_TOOLS): | tools/
+$(CRT_LIBS:lib/%=crt/%): | crt/
+$(OBJS) $(LOBJS): | $(sort $(dir $(OBJS)))
+$(GENH): | arch/$(ARCH)/bits/
+$(GENH_INT): | src/internal/
+include/bits: | include
+
+$(SRC_DIRS):
+	mkdir -p $@
+
 install: install-libs install-headers install-tools
 
 clean:
@@ -82,26 +109,24 @@ include/bits:
 	@test "$(ARCH)" || { echo "Please set ARCH in config.mak before running make." ; exit 1 ; }
 	ln -sf ../arch/$(ARCH)/bits $@
 
-include/bits/alltypes.h.in: include/bits
-
-include/bits/alltypes.h: include/bits/alltypes.h.in include/alltypes.h.in tools/mkalltypes.sed
-	sed -f tools/mkalltypes.sed include/bits/alltypes.h.in include/alltypes.h.in > $@
+include/bits/alltypes.h: $(srcdir)/arch/$(ARCH)/bits/alltypes.h.in $(srcdir)/include/alltypes.h.in $(srcdir)/tools/mkalltypes.sed include/bits
+	sed -f $(srcdir)/tools/mkalltypes.sed $(srcdir)/arch/$(ARCH)/bits/alltypes.h.in $(srcdir)/include/alltypes.h.in > $@
 
-src/internal/version.h: $(wildcard VERSION .git)
-	printf '#define VERSION "%s"\n' "$$(sh tools/version.sh)" > $@
+src/internal/version.h: $(wildcard $(srcdir)/VERSION $(srcdir)/.git)
+	printf '#define VERSION "%s"\n' "$$(cd $(srcdir); sh tools/version.sh)" > $@
 
 src/internal/version.lo: src/internal/version.h
 
-crt/rcrt1.o src/ldso/dlstart.lo src/ldso/dynlink.lo: src/internal/dynlink.h arch/$(ARCH)/reloc.h
+crt/rcrt1.o src/ldso/dlstart.lo src/ldso/dynlink.lo: $(srcdir)/src/internal/dynlink.h $(srcdir)/arch/$(ARCH)/reloc.h
 
-crt/crt1.o crt/Scrt1.o crt/rcrt1.o src/ldso/dlstart.lo: $(wildcard arch/$(ARCH)/crt_arch.h)
+crt/crt1.o crt/scrt1.o crt/rcrt1.o src/ldso/dlstart.lo: $(wildcard $(srcdir)/arch/$(ARCH)/crt_arch.h)
 
-crt/rcrt1.o: src/ldso/dlstart.c
+crt/rcrt1.o: $(srcdir)/src/ldso/dlstart.c
 
 crt/Scrt1.o crt/rcrt1.o: CFLAGS_ALL += -fPIC
 
-OPTIMIZE_SRCS = $(wildcard $(OPTIMIZE_GLOBS:%=src/%))
-$(OPTIMIZE_SRCS:%.c=%.o) $(OPTIMIZE_SRCS:%.c=%.lo): CFLAGS += -O3
+OPTIMIZE_SRCS = $(wildcard $(OPTIMIZE_GLOBS:%=$(srcdir)/src/%))
+$(OPTIMIZE_SRCS:$(srcdir)/%.c=%.o) $(OPTIMIZE_SRCS:$(srcdir)/%.c=%.lo): CFLAGS += -O3
 
 MEMOPS_SRCS = src/string/memcpy.c src/string/memmove.c src/string/memcmp.c src/string/memset.c
 $(MEMOPS_SRCS:%.c=%.o) $(MEMOPS_SRCS:%.c=%.lo): CFLAGS_ALL += $(CFLAGS_MEMOPS)
@@ -119,34 +144,35 @@ $(CRT_LIBS:lib/%=crt/%): CFLAGS_ALL += -DCRT
 # force the corresponding object file to be rebuilt, even if the implicit
 # rule below goes indirectly through a .sub file.
 define mkasmdep
-$(dir $(patsubst %/,%,$(dir $(1))))$(notdir $(1:.s=.o)): $(1)
+$(dir $(patsubst $(srcdir)/%/,%,$(dir $(1))))$(notdir $(1:.s=.o)): $(1)
+$(dir $(patsubst $(srcdir)/%/,%,$(dir $(1))))$(notdir $(1:.s=.lo)): $(1)
 endef
-$(foreach s,$(wildcard src/*/$(ARCH)*/*.s),$(eval $(call mkasmdep,$(s))))
+$(foreach s,$(wildcard $(srcdir)/src/*/$(ARCH)*/*.s),$(eval $(call mkasmdep,$(s))))
 
 # Choose invocation of assembler to be used
 # $(1) is input file, $(2) is output file, $(3) is assembler flags
 ifeq ($(ADD_CFI),yes)
-	AS_CMD = LC_ALL=C awk -f tools/add-cfi.common.awk -f tools/add-cfi.$(ARCH).awk $< | $(CC) -x assembler -c -o $@ -
+	AS_CMD = LC_ALL=C awk -f $(srcdir)/tools/add-cfi.common.awk -f $(srcdir)/tools/add-cfi.$(ARCH).awk $< | $(CC) -x assembler -c -o $@ -
 else
 	AS_CMD = $(CC) -c -o $@ $<
 endif
 
-%.o: $(ARCH)$(ASMSUBARCH)/%.sub
+$(OBJS_SUB): %.o:
 	$(CC) $(CFLAGS_ALL_STATIC) -c -o $@ $(dir $<)$(shell cat $<)
 
-%.o: $(ARCH)/%.s
+$(OBJS_S): %.o:
 	$(AS_CMD) $(CFLAGS_ALL_STATIC)
 
-%.o: %.c $(GENH) $(IMPH)
+$(OBJS_C): %.o: $(srcdir)/%.c $(GENH) $(IMPH)
 	$(CC) $(CFLAGS_ALL_STATIC) -c -o $@ $<
 
-%.lo: $(ARCH)$(ASMSUBARCH)/%.sub
+$(LOBJS_SUB): %.lo:
 	$(CC) $(CFLAGS_ALL_SHARED) -c -o $@ $(dir $<)$(shell cat $<)
 
-%.lo: $(ARCH)/%.s
+$(LOBJS_S): %.lo:
 	$(AS_CMD) $(CFLAGS_ALL_SHARED)
 
-%.lo: %.c $(GENH) $(IMPH)
+$(LOBJS_C): %.lo: $(srcdir)/%.c $(GENH) $(IMPH)
 	$(CC) $(CFLAGS_ALL_SHARED) -c -o $@ $<
 
 lib/libc.so: $(LOBJS)
@@ -166,14 +192,14 @@ $(EMPTY_LIBS):
 lib/%.o: crt/%.o
 	cp $< $@
 
-lib/musl-gcc.specs: tools/musl-gcc.specs.sh config.mak
+lib/musl-gcc.specs: $(srcdir)/tools/musl-gcc.specs.sh config.mak
 	sh $< "$(includedir)" "$(libdir)" "$(LDSO_PATHNAME)" > $@
 
 tools/musl-gcc: config.mak
 	printf '#!/bin/sh\nexec "$${REALGCC:-$(WRAPCC_GCC)}" "$$@" -specs "%s/musl-gcc.specs"\n' "$(libdir)" > $@
 	chmod +x $@
 
-tools/%-clang: tools/%-clang.in config.mak
+tools/%-clang: $(srcdir)/tools/%-clang.in config.mak
 	sed -e 's!@CC@!$(WRAPCC_CLANG)!g' -e 's!@PREFIX@!$(prefix)!g' -e 's!@INCDIR@!$(includedir)!g' -e 's!@LIBDIR@!$(libdir)!g' -e 's!@LDSO@!$(LDSO_PATHNAME)!g' $< > $@
 	chmod +x $@
 
@@ -186,10 +212,13 @@ $(DESTDIR)$(libdir)/%.so: lib/%.so
 $(DESTDIR)$(libdir)/%: lib/%
 	$(INSTALL) -D -m 644 $< $@
 
+$(DESTDIR)$(includedir)/bits/%: $(srcdir)/arch/$(ARCH)/bits/%
+	$(INSTALL) -D -m 644 $< $@
+
 $(DESTDIR)$(includedir)/bits/%: arch/$(ARCH)/bits/%
 	$(INSTALL) -D -m 644 $< $@
 
-$(DESTDIR)$(includedir)/%: include/%
+$(DESTDIR)$(includedir)/%: $(srcdir)/include/%
 	$(INSTALL) -D -m 644 $< $@
 
 $(DESTDIR)$(LDSO_PATHNAME): $(DESTDIR)$(libdir)/libc.so
@@ -202,9 +231,9 @@ install-headers: $(ALL_INCLUDES:include/%=$(DESTDIR)$(includedir)/%)
 install-tools: $(ALL_TOOLS:tools/%=$(DESTDIR)$(bindir)/%)
 
 musl-git-%.tar.gz: .git
-	 git archive --format=tar.gz --prefix=$(patsubst %.tar.gz,%,$@)/ -o $@ $(patsubst musl-git-%.tar.gz,%,$@)
+	 git --git-dir=$(srcdir)/.git archive --format=tar.gz --prefix=$(patsubst %.tar.gz,%,$@)/ -o $@ $(patsubst musl-git-%.tar.gz,%,$@)
 
 musl-%.tar.gz: .git
-	 git archive --format=tar.gz --prefix=$(patsubst %.tar.gz,%,$@)/ -o $@ v$(patsubst musl-%.tar.gz,%,$@)
+	 git --git-dir=$(srcdir)/.git archive --format=tar.gz --prefix=$(patsubst %.tar.gz,%,$@)/ -o $@ v$(patsubst musl-%.tar.gz,%,$@)
 
 .PHONY: all clean install install-libs install-headers install-tools
diff --git a/configure b/configure
index dece1d0..60eb94f 100755
--- a/configure
+++ b/configure
@@ -9,6 +9,9 @@ VAR=VALUE.  See below for descriptions of some of the useful variables.
 
 Defaults for the options are specified in brackets.
 
+Configuration:
+  --srcdir=DIR            source directory [detected]
+
 Installation directories:
   --prefix=PREFIX         main installation prefix [/usr/local/musl]
   --exec-prefix=EPREFIX   installation prefix for executable files [PREFIX]
@@ -117,6 +120,7 @@ CFLAGS_TRY=
 LDFLAGS_AUTO=
 LDFLAGS_TRY=
 OPTIMIZE_GLOBS=
+srcdir=
 prefix=/usr/local/musl
 exec_prefix='$(prefix)'
 bindir='$(exec_prefix)/bin'
@@ -139,6 +143,7 @@ clang_wrapper=no
 for arg ; do
 case "$arg" in
 --help) usage ;;
+--srcdir=*) srcdir=${arg#*=} ;;
 --prefix=*) prefix=${arg#*=} ;;
 --exec-prefix=*) exec_prefix=${arg#*=} ;;
 --bindir=*) bindir=${arg#*=} ;;
@@ -179,11 +184,23 @@ LIBCC=*) LIBCC=${arg#*=} ;;
 esac
 done
 
-for i in prefix exec_prefix bindir libdir includedir syslibdir ; do
+for i in srcdir prefix exec_prefix bindir libdir includedir syslibdir ; do
 stripdir $i
 done
 
 #
+# Get the musl source dir for out-of-tree builds
+#
+if test -z "$srcdir" ; then
+srcdir="${0%/configure}"
+stripdir srcdir
+fi
+abs_builddir="$(pwd)" || fail "$0: cannot determine working directory"
+abs_srcdir="$(cd $srcdir && pwd)" || fail "$0: invalid source directory $srcdir"
+test "$abs_srcdir" = "$abs_builddir" && srcdir=.
+ln -sf $srcdir/Makefile .
+
+#
 # Get a temp filename we can use
 #
 i=0
@@ -321,7 +338,7 @@ __attribute__((__may_alias__))
 #endif
 x;
 EOF
-if $CC $CFLAGS_C99FSE -I./arch/$ARCH -I./include $CPPFLAGS $CFLAGS \
+if $CC $CFLAGS_C99FSE -I$srcdir/arch/$ARCH -I$srcdir/include $CPPFLAGS $CFLAGS \
   -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
 printf "no\n"
 else
@@ -620,7 +637,7 @@ echo '#include <float.h>' > "$tmpc"
 echo '#if LDBL_MANT_DIG == 53' >> "$tmpc"
 echo 'typedef char ldcheck[9-(int)sizeof(long double)];' >> "$tmpc"
 echo '#endif' >> "$tmpc"
-if $CC $CFLAGS_C99FSE -I./arch/$ARCH -I./include $CPPFLAGS $CFLAGS \
+if $CC $CFLAGS_C99FSE -I$srcdir/arch/$ARCH -I$srcdir/include $CPPFLAGS $CFLAGS \
   -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
 printf "yes\n"
 else
@@ -643,6 +660,7 @@ cat << EOF
 ARCH = $ARCH
 SUBARCH = $SUBARCH
 ASMSUBARCH = $ASMSUBARCH
+srcdir = $srcdir
 prefix = $prefix
 exec_prefix = $exec_prefix
 bindir = $bindir
-- 
2.6.0.rc2.230.g3dd15c0