busybox/Makefile.flags

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# ==========================================================================
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# Build system
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# ==========================================================================
BB_VER = $(VERSION).$(PATCHLEVEL).$(SUBLEVEL)$(EXTRAVERSION)
export BB_VER
SKIP_STRIP ?= n
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# -std=gnu99 needed for [U]LLONG_MAX on some systems
CPPFLAGS += $(call cc-option,-std=gnu99,)
CPPFLAGS += \
-Iinclude -Ilibbb \
$(if $(KBUILD_SRC),-Iinclude2 -I$(srctree)/include -I$(srctree)/libbb) \
-include include/autoconf.h \
-D_GNU_SOURCE -DNDEBUG \
$(if $(CONFIG_LFS),-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64) \
build system: remove KBUILD_STR() When using GNU Make >=4.3, the KBUILD_STR() definition interferes badly with dependency checks during build, and forces a complete rebuild every time Make runs. In if_changed_rule, Kconfig checks if the command used to build a file has changed since last execution. The previous command is stored in the generated .<file>.o.cmd file. For example applets/.applets.o.cmd defines a "cmd_applets/applets.o" variable: cmd_applets/applets.o := gcc ... -D"KBUILD_STR(s)=#s" ... Here the '#' should be escaped with a backslash, otherwise GNU Make interprets it as starting a comment, and ignore the rest of the variable. As a result of this truncation, the previous command doesn't equal the new command and Make rebuilds each target. The problem started to appear when GNU Make 4.3 (released January 2020), introduced a backward-incompatible fix to macros containing a '#'. While the above use of '#', a simple Make variable, still needs to be escaped, a '#' within a function invocation doesn't need to be escaped anymore. As Martin Dorey explained on the GNU Make discussion [1], the above declaration is generated from make-cmd, defined as: make-cmd = $(subst \#,\\\#,$(subst $$,$$$$,$(call escsq,$(cmd_$(1)))) Since GNU Make 4.3, the first argument of subst should not have a backslash. make-cmd now looks for literally \# and doesn't find it, and as a result doesn't add the backslash when generating .o.cmd files. [1] http://savannah.gnu.org/bugs/?20513 We could fix it by changing make-cmd to "$(subst #,\#,...)", but to avoid compatibility headaches, simply get rid of the KBUILD_STR definition, as done in Linux by b42841b7bb62 ("kbuild: Get rid of KBUILD_STR"). Quote the string arguments directly rather than asking the preprocessor to quote them. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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-DBB_VER=$(squote)$(quote)$(BB_VER)$(quote)$(squote)
CFLAGS += $(call cc-option,-Wall,)
CFLAGS += $(call cc-option,-Wshadow,)
CFLAGS += $(call cc-option,-Wwrite-strings,)
CFLAGS += $(call cc-option,-Wundef,)
CFLAGS += $(call cc-option,-Wstrict-prototypes,)
CFLAGS += $(call cc-option,-Wunused -Wunused-parameter,)
CFLAGS += $(call cc-option,-Wunused-function -Wunused-value,)
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CFLAGS += $(call cc-option,-Wmissing-prototypes -Wmissing-declarations,)
CFLAGS += $(call cc-option,-Wno-format-security,)
# warn about C99 declaration after statement
CFLAGS += $(call cc-option,-Wdeclaration-after-statement,)
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# If you want to add more -Wsomething above, make sure that it is
# still possible to build bbox without warnings.
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ifeq ($(CONFIG_WERROR),y)
CFLAGS += $(call cc-option,-Werror,)
## TODO:
## gcc version 4.4.0 20090506 (Red Hat 4.4.0-4) (GCC) is a PITA:
## const char *ptr; ... off_t v = *(off_t*)ptr; -> BOOM
## and no easy way to convince it to shut the hell up.
## We have a lot of such things all over the place.
## Classic *(off_t*)(void*)ptr does not work,
## and I am unwilling to do crazy gcc specific ({ void *ppp = ...; })
## stuff in macros. This would obfuscate the code too much.
## Maybe try __attribute__((__may_alias__))?
#CFLAGS += $(call cc-ifversion, -eq, 0404, -fno-strict-aliasing)
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endif
# gcc 3.x emits bogus "old style proto" warning on find.c:alloc_action()
CFLAGS += $(call cc-ifversion, -ge, 0400, -Wold-style-definition)
ifneq ($(CC),clang)
# "clang-9: warning: optimization flag '-finline-limit=0' is not supported
CFLAGS += $(call cc-option,-finline-limit=0,)
endif
CFLAGS += $(call cc-option,-fno-builtin-strlen -fomit-frame-pointer -ffunction-sections -fdata-sections,)
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# -fno-guess-branch-probability: prohibit pseudo-random guessing
# of branch probabilities (hopefully makes bloatcheck more stable):
CFLAGS += $(call cc-option,-fno-guess-branch-probability,)
CFLAGS += $(call cc-option,-funsigned-char,)
ifneq ($(CC),clang)
# "clang-9: warning: argument unused during compilation: '-static-libgcc'"
CFLAGS += $(call cc-option,-static-libgcc,)
endif
CFLAGS += $(call cc-option,-falign-functions=1,)
ifneq ($(CC),clang)
# "clang-9: warning: optimization flag '-falign-jumps=1' is not supported" (and same for other two)
CFLAGS += $(call cc-option,-falign-jumps=1 -falign-labels=1 -falign-loops=1,)
endif
# Defeat .eh_frame bloat (gcc 4.6.3 x86-32 defconfig: 20% smaller busybox binary):
CFLAGS += $(call cc-option,-fno-unwind-tables,)
CFLAGS += $(call cc-option,-fno-asynchronous-unwind-tables,)
# No automatic printf->puts,putchar conversions
# (try disabling this and comparing assembly, it's instructive)
CFLAGS += $(call cc-option,-fno-builtin-printf,)
# clang-9 does not like "str" + N and "if (CONFIG_ITEM && cond)" constructs
ifeq ($(CC),clang)
CFLAGS += $(call cc-option,-Wno-string-plus-int -Wno-constant-logical-operand)
endif
# FIXME: These warnings are at least partially to be concerned about and should
# be fixed..
#CFLAGS += $(call cc-option,-Wconversion,)
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ifneq ($(CONFIG_DEBUG),y)
CFLAGS += $(call cc-option,-Os,$(call cc-option,-O2,))
else
CFLAGS += $(call cc-option,-g,)
#CFLAGS += "-D_FORTIFY_SOURCE=2"
ifeq ($(CONFIG_DEBUG_PESSIMIZE),y)
CFLAGS += $(call cc-option,-O0,)
else
CFLAGS += $(call cc-option,-Os,$(call cc-option,-O2,))
endif
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endif
ifeq ($(CONFIG_DEBUG_SANITIZE),y)
CFLAGS += $(call cc-option,-fsanitize=address,)
CFLAGS += $(call cc-option,-fsanitize=leak,)
CFLAGS += $(call cc-option,-fsanitize=undefined,)
endif
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# If arch/$(ARCH)/Makefile did not override it (with, say, -fPIC)...
ARCH_FPIC ?= -fpic
ARCH_FPIE ?= -fpie
ARCH_PIE ?= -pie
# Usage: $(eval $(call pkg_check_modules,VARIABLE-PREFIX,MODULES))
define pkg_check_modules
$(1)_CFLAGS := $(shell $(PKG_CONFIG) $(PKG_CONFIG_FLAGS) --cflags $(2))
$(1)_LIBS := $(shell $(PKG_CONFIG) $(PKG_CONFIG_FLAGS) --libs $(2))
endef
ifeq ($(CONFIG_BUILD_LIBBUSYBOX),y)
# on i386: 14% smaller libbusybox.so
# (code itself is 9% bigger, we save on relocs/PLT/GOT)
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CFLAGS += $(ARCH_FPIC)
# and another 4% reduction of libbusybox.so:
# (external entry points must be marked EXTERNALLY_VISIBLE)
CFLAGS += $(call cc-option,-fvisibility=hidden)
endif
ifeq ($(CONFIG_STATIC),y)
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CFLAGS_busybox += -static
PKG_CONFIG_FLAGS += --static
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endif
ifeq ($(CONFIG_PIE),y)
CFLAGS_busybox += $(ARCH_PIE)
CFLAGS += $(ARCH_FPIE)
endif
ifneq ($(CONFIG_EXTRA_CFLAGS),)
CFLAGS += $(strip $(subst ",,$(CONFIG_EXTRA_CFLAGS)))
#"))
endif
# Note: both "" (string consisting of two quote chars) and empty string
# are possible, and should be skipped below.
ifneq ($(subst "",,$(CONFIG_SYSROOT)),)
CFLAGS += --sysroot=$(CONFIG_SYSROOT)
export SYSROOT=$(CONFIG_SYSROOT)
endif
# Android has no separate crypt library
# gcc-4.2.1 fails if we try to feed C source on stdin:
# echo 'int main(void){return 0;}' | $(CC) $(CFLAGS) -lcrypt -o /dev/null -xc -
# fall back to using a temp file:
CRYPT_AVAILABLE := $(shell echo 'int main(void){return 0;}' >crypttest.c; $(CC) $(CFLAGS) -lcrypt -o /dev/null crypttest.c >/dev/null 2>&1 && echo "y"; rm crypttest.c)
ifeq ($(CRYPT_AVAILABLE),y)
LDLIBS += m rt crypt
else
LDLIBS += m rt
endif
# libm may be needed for dc, awk, ntpd
# librt may be needed for clock_gettime()
# libpam may use libpthread, libdl and/or libaudit.
# On some platforms that requires an explicit -lpthread, -ldl, -laudit.
# However, on *other platforms* it fails when some of those flags
# given needlessly. On some systems, crypt needs pthread.
#
# I even had a system where a runtime test for pthread
# (similar to CRYPT_AVAILABLE test above) was not reliable.
#
# Do not propagate this mess by adding libraries to CONFIG_PAM/CRYPT_AVAILABLE blocks.
# Add libraries you need to CONFIG_EXTRA_LDLIBS instead.
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ifeq ($(CONFIG_PAM),y)
LDLIBS += pam pam_misc
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endif
ifeq ($(CONFIG_SELINUX),y)
SELINUX_PC_MODULES = libselinux libsepol
$(eval $(call pkg_check_modules,SELINUX,$(SELINUX_PC_MODULES)))
CPPFLAGS += $(SELINUX_CFLAGS)
LDLIBS += $(if $(SELINUX_LIBS),$(SELINUX_LIBS:-l%=%),$(SELINUX_PC_MODULES:lib%=%))
endif
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ifeq ($(CONFIG_FEATURE_NSLOOKUP_BIG),y)
LDLIBS += resolv
endif
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ifeq ($(CONFIG_EFENCE),y)
LDLIBS += efence
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endif
ifeq ($(CONFIG_DMALLOC),y)
LDLIBS += dmalloc
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endif
# If a flat binary should be built, CFLAGS_busybox="-elf2flt"
# env var should be set for make invocation.
# Here we check whether CFLAGS_busybox indeed contains that flag.
# (For historical reasons, we also check LDFLAGS, which doesn't
# seem to be entirely correct variable to put "-elf2flt" into).
W_ELF2FLT = -elf2flt
ifneq (,$(findstring $(W_ELF2FLT),$(LDFLAGS) $(CFLAGS_busybox)))
SKIP_STRIP = y
endif
ifneq ($(CONFIG_EXTRA_LDFLAGS),)
LDFLAGS += $(strip $(subst ",,$(CONFIG_EXTRA_LDFLAGS)))
#"))
endif
ifneq ($(CONFIG_EXTRA_LDLIBS),)
LDLIBS += $(strip $(subst ",,$(CONFIG_EXTRA_LDLIBS)))
#"))
endif
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# Busybox is a stack-fatty so make sure we increase default size
# TODO: use "make stksizes" to find & fix big stack users
# (we stole scripts/checkstack.pl from the kernel... thanks guys!)
# Reduced from 20k to 16k in 1.9.0.
FLTFLAGS += -s 16000