[PATCH 12/13] flex-array: warn on flexible array in nested aggregate types

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

A structure or a union containing another aggregate type containing,
possibly recursively, a flexible array is quite error prone and make
not much sense. So, add an option -Wflexible-array-nested to warn
on such usage.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
 options.c                      | 2 ++
 options.h                      | 1 +
 sparse.1                       | 7 +++++++
 symbol.c                       | 4 ++++
 validation/flex-array-nested.c | 1 -
 5 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/options.c b/options.c
index a8129ac1e952..b46900b973a6 100644
--- a/options.c
+++ b/options.c
@@ -101,6 +101,7 @@ int Wdo_while = 0;
 int Wenum_mismatch = 1;
 int Wexternal_function_has_definition = 1;
 int Wflexible_array_array = 1;
+int Wflexible_array_nested = 0;
 int Wflexible_array_sizeof = 0;
 int Wimplicit_int = 1;
 int Winit_cstring = 0;
@@ -843,6 +844,7 @@ static const struct flag warnings[] = {
 	{ "enum-mismatch", &Wenum_mismatch },
 	{ "external-function-has-definition", &Wexternal_function_has_definition },
 	{ "flexible-array-array", &Wflexible_array_array },
+	{ "flexible-array-nested", &Wflexible_array_nested },
 	{ "flexible-array-sizeof", &Wflexible_array_sizeof },
 	{ "implicit-int", &Wimplicit_int },
 	{ "init-cstring", &Winit_cstring },
diff --git a/options.h b/options.h
index 7bcf925b6912..d23ed472eaac 100644
--- a/options.h
+++ b/options.h
@@ -100,6 +100,7 @@ extern int Wdo_while;
 extern int Wenum_mismatch;
 extern int Wexternal_function_has_definition;
 extern int Wflexible_array_array;
+extern int Wflexible_array_nested;
 extern int Wflexible_array_sizeof;
 extern int Wimplicit_int;
 extern int Winit_cstring;
diff --git a/sparse.1 b/sparse.1
index c1a74153c618..9b1a59c6b9d4 100644
--- a/sparse.1
+++ b/sparse.1
@@ -264,6 +264,13 @@ Sparse issues these warnings by default. To turn them off, use
 \fB-Wno-flexible-array-array\fR.
 .
 .TP
+.B -Wflexible-array-nested
+Warn about structures containing a flexible array being contained into
+another structure, union or array.
+
+Sparse does not issue these warnings by default.
+.
+.TP
 .B -Wflexible-array-sizeof
 Warn about using the sizeof operator on a structure containing a flexible array,
 possibly recursively.
diff --git a/symbol.c b/symbol.c
index 02b9066e966a..a9f646eb053f 100644
--- a/symbol.c
+++ b/symbol.c
@@ -197,6 +197,10 @@ static struct symbol * examine_struct_union_type(struct symbol *sym, int advance
 				info.max_align = member->ctype.alignment;
 		}
 
+		if (has_flexible_array(member))
+			info.has_flex_array = 1;
+		if (has_flexible_array(member) && Wflexible_array_nested)
+			warning(sym->pos, "nested flexible arrays");
 		fn(member, &info);
 	} END_FOR_EACH_PTR(member);
 
diff --git a/validation/flex-array-nested.c b/validation/flex-array-nested.c
index 3503c329d7c3..63767683c56a 100644
--- a/validation/flex-array-nested.c
+++ b/validation/flex-array-nested.c
@@ -21,7 +21,6 @@ static int foo(struct s *s, union u *u)
 /*
  * check-name: flex-array-nested
  * check-command: sparse -Wflexible-array-nested $file
- * check-known-to-fail
  *
  * check-error-start
 flex-array-nested.c:6:8: warning: nested flexible arrays
-- 
2.28.0