[PATCH v2] let function definition inherit prototype attributes

[Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>]

It's common to declare a function with the attribute
'pure' or 'noreturn' and to omit the attribute in the
function definition. It mak somehow sense since the
information conveyed by these attributes are destined
to the function users not the function itself.

So, when checking declaration/definition, let the
current symbol inherit any function attributes present
in previous declarations.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---

The patch is also available for review & testing at:
	git://github.com/lucvoo/sparse-dev.git fun-attr-inherit

Changes since v1:
* the old name was 'allow omitted function attribute in definition'
* change the approach: instead of filtering out these attributes at
  check-time, let's inherit them at declaration-time.


 symbol.c                                                 | 9 +++++++++
 ...ion-attribute-omitted.c => function-redecl-funattr.c} | 3 +--
 validation/function-redecl2.c                            | 3 ---
 3 files changed, 10 insertions(+), 5 deletions(-)
 rename validation/{function-attribute-omitted.c => function-redecl-funattr.c} (75%)

diff --git a/symbol.c b/symbol.c
index 90149e5ae..bafa7c432 100644
--- a/symbol.c
+++ b/symbol.c
@@ -588,6 +588,14 @@ struct symbol *befoul(struct symbol *type)
 	return NULL;
 }
 
+static void inherit_declaration(struct symbol *sym, struct symbol *prev)
+{
+	unsigned long mods = prev->ctype.modifiers;
+
+	// inherit function attributes
+	sym->ctype.modifiers |= mods & MOD_FUN_ATTR;
+}
+
 void check_declaration(struct symbol *sym)
 {
 	int warned = 0;
@@ -598,6 +606,7 @@ void check_declaration(struct symbol *sym)
 			continue;
 		if (sym->scope == next->scope) {
 			sym->same_symbol = next;
+			inherit_declaration(sym, next);
 			return;
 		}
 		/* Extern in block level matches a TOPLEVEL non-static symbol */
diff --git a/validation/function-attribute-omitted.c b/validation/function-redecl-funattr.c
similarity index 75%
rename from validation/function-attribute-omitted.c
rename to validation/function-redecl-funattr.c
index 43b301d8f..b1e2fb195 100644
--- a/validation/function-attribute-omitted.c
+++ b/validation/function-redecl-funattr.c
@@ -9,6 +9,5 @@ void __noreturn	n(void);
 void		n(void) { while (1) ; }
 
 /*
- * check-name: function-attribute-omitted
- * check-known-to-fail
+ * check-name: function-redecl-funattr
  */
diff --git a/validation/function-redecl2.c b/validation/function-redecl2.c
index 3435aa00c..ef396137a 100644
--- a/validation/function-redecl2.c
+++ b/validation/function-redecl2.c
@@ -25,7 +25,4 @@ void func2(int a)
 
 /*
  * check-name: function-redecl2
- *
- * check-known-to-fail
- *
  */
-- 
2.24.0