[stalld v2 2/6] Makefile: Improve compiler flag detection for -fcf-protection

[Wander Lairson Costa <wander@redhat.com>]

The previous method of detecting support for -fcf-protection relied on
a minimum GCC version check, which was not always accurate and could
fail on different architectures or compiler toolchains.

This commit replaces the version check with a more robust method that
directly tests if the compiler supports the -fcf-protection flag. This
ensures better portability and avoids compilation errors on systems
where the flag is not available.

This change mirrors the recently added detection logic for the
-mno-omit-leaf-frame-pointer flag.

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Cc: Derek Barbosa <debarbos@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Chunsheng Luo <luochunsheng@ustc.edu>
---
 Makefile | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/Makefile b/Makefile
index d605e60..23e786d 100644
--- a/Makefile
+++ b/Makefile
@@ -20,17 +20,14 @@ IS_MINVER := $(intcmp $(GCC_VER), $(MIN_GCC_VER), false, true, true)
 $(info IS_MINVER=$(IS_MINVER))
 
 USE_BPF := 1
-FCF_PROTECTION := -fcf-protection
 MTUNE	:= -mtune=generic
 M64	:= -m64
 
 ifeq ($(ARCH),aarch64)
-FCF_PROTECTION := "-fcf-protection=none"
 M64	:=
 endif
 ifeq ($(ARCH),i686)
 USE_BPF := 0
-FCF_PROTECTION := "-fcf-protection=branch"
 endif
 ifeq ($(ARCH),s390x)
 MTUNE := -mtune=z13
@@ -43,23 +40,23 @@ ifeq ($(ARCH),powerpc)
 USE_BPF := 0
 MTUNE := -mtune=powerpc
 endif
-ifeq ($(strip $(IS_MINVER)), false)
-FCF_PROTECTION := 
-endif
-
-
-$(info USE_BPF=$(USE_BPF))
-$(info FCF_PROTECTION=$(FCF_PROTECTION))
-$(info MTUNE=$(MTUNE))
 
 DEBUG	?=	0
 
 INSTALL	=	install
 CC	:=	gcc
+
+# Test if compiler supports -fcf-protection
+FCF_PROTECTION := $(shell echo 'int main(void){return 0;}' | \
+		$(CC) -x c -fcf-protection - \
+		-o /dev/null 2>/dev/null && \
+		echo '-fcf-protection')
+
 FOPTS	:=	-flto=auto -ffat-lto-objects -fexceptions -fstack-protector-strong \
 		-fasynchronous-unwind-tables -fstack-clash-protection -fno-omit-frame-pointer \
 		$(strip $(FCF_PROTECTION)) -fpie
 
+
 # Test if compiler supports -mno-omit-leaf-frame-pointer
 OMIT_LEAF_FP := $(shell echo 'int main(void){return 0;}' | \
 		$(CC) -x c -mno-omit-leaf-frame-pointer - \
@@ -74,6 +71,10 @@ DEFS	:=	-DUSE_BPF=$(USE_BPF) -D_FORTIFY_SOURCE=3 -D_GLIBCXX_ASSERTIONS -DDEBUG_S
 
 CFLAGS	:=      -DVERSION=\"$(VERSION)\" $(FOPTS) $(MOPTS) $(WOPTS) $(DEFS)
 
+$(info USE_BPF=$(USE_BPF))
+$(info FCF_PROTECTION=$(FCF_PROTECTION))
+$(info MTUNE=$(MTUNE))
+
 ifeq ($(DEBUG),0)
 CFLAGS	+=	-g -O2
 else
-- 
2.51.1