# Test if the input language was specified externally.
# Otherwise test if the compiler unterstands the "-std=c99" flag, and use it if so.
ifeq ($(filter -std=%,$(CFLAGS)),)
  ifeq ($(shell $(CC) -std=c99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
    CFLAGS += -std=gnu99
  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

    ifneq ($(shell $(CXX) -fno-delete-null-pointer-checks -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
      CXXUWFLAGS += -fno-delete-null-pointer-checks
    else
      ifneq ($(shell LANG=C $(CXX) -fno-delete-null-pointer-checks -E - 2>&1 1>/dev/null </dev/null | grep warning: | grep -- -fno-delete-null-pointer-checks),)
        CXXUWFLAGS += -fno-delete-null-pointer-checks
      endif
    endif
  endif
endif

# Use colored compiler output if the compiler supports this and if this is not
# disabled by the user
ifeq ($(CC_NOCOLOR),0)
  ifeq ($(shell $(CC) -fdiagnostics-color -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
    CFLAGS += -fdiagnostics-color
  endif
endif

# Fast-out on old style function definitions.
# They cause unreadable error compiler errors on missing semicolons.
# Worse yet they hide errors by accepting wildcard argument types.
ifeq ($(shell $(CC) -Wstrict-prototypes -Werror=strict-prototypes -Wold-style-definition -Werror=old-style-definition -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
  # duplicated parameters don't hurt
  CFLAGS += -Wstrict-prototypes -Wold-style-definition
  CXXUWFLAGS += -Wstrict-prototypes -Wold-style-definition
  ifeq ($(WERROR),1)
    CFLAGS += -Werror=strict-prototypes -Werror=old-style-definition
  endif
endif

# Unwanted flags for c++
CXXUWFLAGS += -std=%

ifeq ($(LTO),1)
  $(warning Building with Link-Time-Optimizations is currently an experimental feature. Expect broken binaries.)
  LTOFLAGS = -flto
  LINKFLAGS += ${LTOFLAGS}
endif

# Forbid common symbols to prevent accidental aliasing.
CFLAGS += -fno-common

# Enable all default warnings
CFLAGS += -Wall

ifeq (,$(filter -DDEVELHELP,$(CFLAGS)))
  ifneq (1,$(FORCE_ASSERTS))
    CFLAGS += -DNDEBUG
  endif
endif

# Default ARFLAGS for platforms which do not specify it.
# Note: make by default provides ARFLAGS=rv which we want to override
ifeq ($(origin ARFLAGS),default)
  ARFLAGS = rcs
endif

# 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.
TMPOUT := $(shell mktemp -d)
try-run = $(shell set -e;        \
  TMP=$(TMPOUT)/tmp;             \
  TMPO=$(TMPOUT)/tmp.o;          \
  mkdir -p $(TMPOUT);            \
  trap "rm -rf $(TMPOUT)" EXIT;  \
  if ($(1)) >/dev/null 2>&1;     \
  then echo "$(2)";              \
  else echo "$(3)";              \
  fi)

# __cc-option
# Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586)
__cc-option = $(call try-run,\
  $(1) -Werror $(2) $(3) -c -x c /dev/null -o "$$TMP",$(3),$(4))

# cc-option
# Usage: CFLAGS += $(call cc-option,-mthumb)
cc-option = $(call __cc-option, $(CC),$(CFLAGS),$(1),$(2))

# ld-option
# Usage: LDFLAGS += $(call ld-option, -X, -Y)
ld-option = $(call try-run, $(LD) $(LDFLAGS) $(1) -v,$(1),$(2),$(3))

LDARG += $(call ld-option,--no-warn-rwx-segment)

LDARGPREFIX = -Wl,
LDARG := $(strip $(LDARG))
ifneq (,$(LDARG))
  LINKFLAGS += $(addprefix $(LDARGPREFIX), $(LDARG))
endif