[PATCH 71/73] x86: Undefine conflicting bitness macros when parsing -m flags

[Bart Van Assche <bvanassche@acm.org>]

Emit #undef directives for conflicting x86 bitness macros in
handle_mbitness() in options.c at the command-line position of -m16,
-m32, -m64, or -mx32, while preserving explicit -D macro definitions
that appear later on the command line.

Prevent inconsistent word size errors and static assertion failures in
the Linux kernel when real-mode 16-bit code is compiled under an x86_64
kernel build that passes -D__x86_64__ before -m16 in CHECKFLAGS, and add
validation/arch/x86-bitness-undef.c and x86-bitness-override.c.

Fixes: efd9af566c05 ("arch: move target-specific predefines...")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 options.c                              | 58 +++++++++++++++++++++++---
 validation/arch/x86-bitness-override.c | 17 ++++++++
 validation/arch/x86-bitness-undef.c    | 16 +++++++
 3 files changed, 85 insertions(+), 6 deletions(-)
 create mode 100644 validation/arch/x86-bitness-override.c
 create mode 100644 validation/arch/x86-bitness-undef.c

diff --git a/options.c b/options.c
index 2de74afc5c35..2e6e2ce0c2ea 100644
--- a/options.c
+++ b/options.c
@@ -671,13 +671,59 @@ static char **handle_multiarch_dir(char *arg, char **next)
 	return next;
 }
 
+static int handle_mbitness(const char *arg, const char *opt, const struct flag *flag, int options)
+{
+	if (opt[0] != '\0' || (options & OPT_INVERSE))
+		return 0;
+	*flag->flag = flag->val;
+	if (arch_target->mach == MACH_I386 || arch_target->mach == MACH_X86_64) {
+		switch (flag->val) {
+		case ARCH_LP32:
+			add_pre_buffer("#undef __x86_64__\n"
+				       "#undef __x86_64\n"
+				       "#undef __amd64__\n"
+				       "#undef __amd64\n"
+				       "#ifndef __i386__\n"
+				       "#define __i386__ 1\n"
+				       "#endif\n"
+				       "#ifndef __i386\n"
+				       "#define __i386 1\n"
+				       "#endif\n"
+				       "#if !defined(__STRICT_ANSI__) && !defined(i386)\n"
+				       "#define i386 1\n"
+				       "#endif\n");
+			break;
+		case ARCH_LP64:
+		case ARCH_X32:
+		case ARCH_LLP64:
+			add_pre_buffer("#undef __i386__\n"
+				       "#undef __i386\n"
+				       "#undef i386\n"
+				       "#ifndef __x86_64__\n"
+				       "#define __x86_64__ 1\n"
+				       "#endif\n"
+				       "#ifndef __x86_64\n"
+				       "#define __x86_64 1\n"
+				       "#endif\n"
+				       "#ifndef __amd64__\n"
+				       "#define __amd64__ 1\n"
+				       "#endif\n"
+				       "#ifndef __amd64\n"
+				       "#define __amd64 1\n"
+				       "#endif\n");
+			break;
+		}
+	}
+	return 1;
+}
+
 static const struct flag mflags[] = {
-	{ "64", &arch_m64, NULL, OPT_VAL, ARCH_LP64 },
-	{ "32", &arch_m64, NULL, OPT_VAL, ARCH_LP32 },
-	{ "31", &arch_m64, NULL, OPT_VAL, ARCH_LP32 },
-	{ "16", &arch_m64, NULL, OPT_VAL, ARCH_LP32 },
-	{ "x32",&arch_m64, NULL, OPT_VAL, ARCH_X32 },
-	{ "size-llp64", &arch_m64, NULL, OPT_VAL, ARCH_LLP64 },
+	{ "64", &arch_m64, handle_mbitness, OPT_VAL, ARCH_LP64 },
+	{ "32", &arch_m64, handle_mbitness, OPT_VAL, ARCH_LP32 },
+	{ "31", &arch_m64, handle_mbitness, OPT_VAL, ARCH_LP32 },
+	{ "16", &arch_m64, handle_mbitness, OPT_VAL, ARCH_LP32 },
+	{ "x32",&arch_m64, handle_mbitness, OPT_VAL, ARCH_X32 },
+	{ "size-llp64", &arch_m64, handle_mbitness, OPT_VAL, ARCH_LLP64 },
 	{ "size-long", &arch_msize_long },
 	{ "arch=", NULL, handle_march },
 	{ "big-endian", &arch_big_endian, NULL },
diff --git a/validation/arch/x86-bitness-override.c b/validation/arch/x86-bitness-override.c
new file mode 100644
index 000000000000..ac51ecb244a8
--- /dev/null
+++ b/validation/arch/x86-bitness-override.c
@@ -0,0 +1,17 @@
+#ifdef __x86_64__
+defined_x86_64
+#endif
+#ifdef __i386__
+defined_i386
+#endif
+
+/*
+ * check-name: arch/x86-bitness-override
+ * check-command: sparse --arch=x86_64 -m16 -D__x86_64__ -E $file
+ *
+ * check-output-start
+
+defined_x86_64
+defined_i386
+ * check-output-end
+ */
diff --git a/validation/arch/x86-bitness-undef.c b/validation/arch/x86-bitness-undef.c
new file mode 100644
index 000000000000..ab2434c1173b
--- /dev/null
+++ b/validation/arch/x86-bitness-undef.c
@@ -0,0 +1,16 @@
+#ifdef __x86_64__
+defined_x86_64
+#endif
+#ifdef __i386__
+defined_i386
+#endif
+
+/*
+ * check-name: arch/x86-bitness-undef
+ * check-command: sparse --arch=x86_64 -D__x86_64__ -m16 -E $file
+ *
+ * check-output-start
+
+defined_i386
+ * check-output-end
+ */