We need to check if some compiler flags are supported as not all compilers may do so. For instance, "-Wsuggest-attribute=format" is supported by gcc but not by clang. Using a compiler option that is not supported will most likely cause the build to fail, since we are building with "-Werror" and the compiler will issue a warning about the unknown option. As a result, we only use the option if the compiler understands it. Signed-off-by: Markus Mayer <mmayer@xxxxxxxxxxxx> --- Makefile | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index f1f0ab368cd3..febdca5742c5 100644 --- a/Makefile +++ b/Makefile @@ -3,6 +3,26 @@ # Device Tree Compiler # +# try-run and cc-option were stolen from the Linux kernel +TMPOUT = .tmp_$$$$ +# try-run +# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise) +# Exit code chooses option. "$$TMP" serves as a temporary file and is +# automatically cleaned up. +try-run = $(shell set -e; \ + TMP=$(TMPOUT)/tmp; \ + mkdir -p $(TMPOUT); \ + trap "rm -rf $(TMPOUT)" EXIT; \ + if ($(1)) >/dev/null 2>&1; \ + then echo "$(2)"; \ + else echo "$(3)"; \ + fi) + +# cc-option +# Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586) +cc-option = $(call try-run, \ + $(CC) -Werror $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2)) + # # Version information will be constructed in this order: # DTC_VERSION release version as MAJOR.MINOR.PATCH @@ -18,9 +38,12 @@ CONFIG_LOCALVERSION = ASSUME_MASK ?= 0 CPPFLAGS = -I libfdt -I . -DFDT_ASSUME_MASK=$(ASSUME_MASK) +# Warnings where we need to check they are supported +OPT_WARNINGS = $(call cc-option,-Wsuggest-attribute=format) +# Regular warnings WARNINGS = -Wall -Wpointer-arith -Wcast-qual -Wnested-externs -Wsign-compare \ -Wstrict-prototypes -Wmissing-prototypes -Wredundant-decls -Wshadow \ - -Wsuggest-attribute=format -Wwrite-strings + -Wwrite-strings $(OPT_WARNINGS) CFLAGS = -g -Os $(SHAREDLIB_CFLAGS) -Werror $(WARNINGS) $(EXTRA_CFLAGS) BISON = bison -- 2.46.0
