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# Test if the input language was specified externally.
# Otherwise test if the compiler unterstands the "-std=gnu99" flag, and use it if so.
# Otherwise test if the compiler unterstands the "-std=c99" flag, and use it if so.
ifeq ($(filter -std=%,$(CFLAGS)),)
ifeq ($(shell $(CC) -std=gnu99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
CFLAGS += -std=gnu99
else
ifeq ($(shell $(CC) -std=c99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
CFLAGS += -std=c99
endif
endif
endif
# Add `-fno-delete-null-pointer-checks` flag iff the compiler supports it.
# GCC removes moves tests whether `x == NULL`, if previously `x` or even `x->y` was accessed.
# 0x0 might be a sane memory location for embedded systems, so the test must not be removed.
# Right now clang does not use the *delete-null-pointer* optimization, and does not understand the parameter.
# Related issues: #628, #664.
ifeq ($(shell $(CC) -fno-delete-null-pointer-checks -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
ifeq ($(shell LANG=C $(CC) -fno-delete-null-pointer-checks -E - 2>&1 1>/dev/null </dev/null | grep warning: | grep -- -fno-delete-null-pointer-checks),)
CFLAGS += -fno-delete-null-pointer-checks
endif
endif