evaluate: externally_visible functions don't need a declaration

sparse warns for non-static functions that don't have a separate
declaration. The kernel contains several such functions that are marked
as __attribute__((externally_visible)) to mark that they are called from
assembly code. Assembly code doesn't need a header with a declaration to
call a function. Therefore, suppress the warning for functions with
__attribute__((externally_visible)).

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>

4 files changed, 19 insertions, 4 deletions

diff --git a/evaluate.c b/evaluate.c
index cedd1330..7c63d788 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -3387,7 +3387,7 @@ void check_duplicates(struct symbol *sym)
 	}
 	if (!declared) {
 		unsigned long mod = sym->ctype.modifiers;
-		if (mod & (MOD_STATIC | MOD_REGISTER))
+		if (mod & (MOD_STATIC | MOD_REGISTER | MOD_EXT_VISIBLE))
 			return;
 		if (!(mod & MOD_TOPLEVEL))
 			return;
diff --git a/gcc-attr-list.h b/gcc-attr-list.h
index 8da31435..c7800175 100644
--- a/gcc-attr-list.h
+++ b/gcc-attr-list.h
@@ -42,7 +42,6 @@ GCC_ATTR(either)
 GCC_ATTR(error)
 GCC_ATTR(exception)
 GCC_ATTR(exception_handler)
-GCC_ATTR(externally_visible)
 GCC_ATTR(far)
 GCC_ATTR(fast_interrupt)
 GCC_ATTR(fastcall)
diff --git a/parse.c b/parse.c
index 79543432..f291e247 100644
--- a/parse.c
+++ b/parse.c
@@ -82,6 +82,7 @@ typedef struct token *attr_t(struct token *, struct symbol *,
 
 static attr_t
 	attribute_packed, attribute_aligned, attribute_modifier,
+	attribute_ext_visible,
 	attribute_bitwise,
 	attribute_address_space, attribute_context,
 	attribute_designated_init,
@@ -373,6 +374,10 @@ static struct symbol_op attr_mod_op = {
 	.attribute = attribute_modifier,
 };
 
+static struct symbol_op ext_visible_op = {
+	.attribute = attribute_ext_visible,
+};
+
 static struct symbol_op attr_bitwise_op = {
 	.attribute = attribute_bitwise,
 };
@@ -562,6 +567,8 @@ static struct init_keyword {
 	{"const",	NS_KEYWORD,	MOD_PURE,	.op = &attr_mod_op },
 	{"__const",	NS_KEYWORD,	MOD_PURE,	.op = &attr_mod_op },
 	{"__const__",	NS_KEYWORD,	MOD_PURE,	.op = &attr_mod_op },
+	{"externally_visible",	NS_KEYWORD,	.op = &ext_visible_op },
+	{"__externally_visible__",	NS_KEYWORD,	.op = &ext_visible_op },
 
 	{ "mode",	NS_KEYWORD,	.op = &mode_op },
 	{ "__mode__",	NS_KEYWORD,	.op = &mode_op },
@@ -1106,6 +1113,12 @@ static struct token *attribute_modifier(struct token *token, struct symbol *attr
 	return token;
 }
 
+static struct token *attribute_ext_visible(struct token *token, struct symbol *attr, struct decl_state *ctx)
+{
+	ctx->is_ext_visible = 1;
+	return token;
+}
+
 static struct token *attribute_bitwise(struct token *token, struct symbol *attr, struct decl_state *ctx)
 {
 	if (Wbitwise)
@@ -1343,7 +1356,8 @@ static unsigned long storage_modifiers(struct decl_state *ctx)
 		[SRegister] = MOD_REGISTER
 	};
 	return mod[ctx->storage_class] | (ctx->is_inline ? MOD_INLINE : 0)
-		| (ctx->is_tls ? MOD_TLS : 0);
+		| (ctx->is_tls ? MOD_TLS : 0)
+		| (ctx->is_ext_visible ? MOD_EXT_VISIBLE : 0);
 }
 
 static void set_storage_class(struct position *pos, struct decl_state *ctx, int class)
diff --git a/symbol.h b/symbol.h
index 51e1c867..ac43b314 100644
--- a/symbol.h
+++ b/symbol.h
@@ -110,6 +110,7 @@ struct decl_state {
 	struct ident **ident;
 	struct symbol_op *mode;
 	unsigned char prefer_abstract, is_inline, storage_class, is_tls;
+	unsigned char is_ext_visible;
 };
 
 struct symbol_op {
@@ -237,6 +238,7 @@ struct symbol {
 #define MOD_NOCAST		0x04000000
 #define MOD_NODEREF		0x08000000
 #define MOD_NORETURN		0x10000000
+#define MOD_EXT_VISIBLE		0x20000000
 
 
 #define MOD_ACCESS	(MOD_ASSIGNED | MOD_ADDRESSABLE)
@@ -246,7 +248,7 @@ struct symbol {
 #define MOD_LONG_ALL	(MOD_LONG | MOD_LONGLONG | MOD_LONGLONGLONG)
 #define MOD_SPECIFIER	(MOD_CHAR | MOD_SHORT | MOD_LONG_ALL | MOD_SIGNEDNESS)
 #define MOD_SIZE	(MOD_CHAR | MOD_SHORT | MOD_LONG_ALL)
-#define MOD_IGNORE	(MOD_STORAGE | MOD_ACCESS | MOD_USERTYPE | MOD_EXPLICITLY_SIGNED)
+#define MOD_IGNORE	(MOD_STORAGE | MOD_ACCESS | MOD_USERTYPE | MOD_EXPLICITLY_SIGNED | MOD_EXT_VISIBLE)
 #define	MOD_QUALIFIER	(MOD_CONST | MOD_VOLATILE | MOD_RESTRICT | MOD_ATOMIC)
 #define MOD_PTRINHERIT	(MOD_QUALIFIER | MOD_NODEREF | MOD_NORETURN | MOD_NOCAST)
 /* modifiers preserved by typeof() operator */