slotinfo in struct dtv_slotinfo_list should be flexible array [BZ #25097]

GCC 10 will warn about subscribing inner length zero arrays.  Use a GCC
extension in csu/libc-tls.c to allocate space for the static_slotinfo
variable.  Adjust nptl_db so that the type description machinery does
not attempt to determine the size of the flexible array member slotinfo.

Change-Id: I51be146a7857186a4ede0bb40b332509487bdde8

4 files changed, 14 insertions, 1 deletions

diff --git a/nptl_db/db-symbols.h b/nptl_db/db-symbols.h
index 8b078b013e..7c53d803bf 100644
--- a/nptl_db/db-symbols.h
+++ b/nptl_db/db-symbols.h
@@ -25,6 +25,7 @@
   DB_LOOKUP_NAME (SYM_SIZEOF_##type, _thread_db_sizeof_##type)
 #define DB_STRUCT_FIELD(type, field) \
   DB_LOOKUP_NAME (SYM_##type##_FIELD_##field, _thread_db_##type##_##field)
+#define DB_STRUCT_FLEXIBLE_ARRAY(type, field) DB_STRUCT_FIELD (type, field)
 #define DB_SYMBOL(name) \
   DB_LOOKUP_NAME (SYM_##name, name)
 #define DB_FUNCTION(name) \
@@ -36,6 +37,8 @@
 # include "structs.def"
 
 # undef DB_STRUCT
+# undef DB_STRUCT_FIELD
+# undef DB_STRUCT_FLEXIBLE_ARRAY
 # undef DB_FUNCTION
 # undef DB_SYMBOL
 # undef DB_VARIABLE
diff --git a/nptl_db/db_info.c b/nptl_db/db_info.c
index af7f754b32..40efe1a29b 100644
--- a/nptl_db/db_info.c
+++ b/nptl_db/db_info.c
@@ -56,6 +56,9 @@ extern bool __nptl_initial_report_events;
   DB_DEFINE_DESC (name, \
 		  8 * sizeof (obj)[0], sizeof (obj) / sizeof (obj)[0], \
 		  offset);
+/* Flexible arrays do not have a length that can be determined.  */
+#define FLEXIBLE_ARRAY_DESC(name, offset, obj) \
+  DB_DEFINE_DESC (name, 8 * sizeof (obj)[0], 0, offset);
 
 #if TLS_TCB_AT_TP
 # define dtvp header.dtv
@@ -77,6 +80,9 @@ DESC (_thread_db_pthread_dtvp,
 #define DB_STRUCT_ARRAY_FIELD(type, field) \
   ARRAY_DESC (_thread_db_##type##_##field, \
 	      offsetof (type, field), ((type *) 0)->field)
+#define DB_STRUCT_FLEXIBLE_ARRAY(type, field) \
+  FLEXIBLE_ARRAY_DESC (_thread_db_##type##_##field, \
+		       offsetof (type, field), ((type *) 0)->field)
 #define DB_VARIABLE(name) DESC (_thread_db_##name, 0, name)
 #define DB_ARRAY_VARIABLE(name) ARRAY_DESC (_thread_db_##name, 0, name)
 #define DB_SYMBOL(name)	/* Nothing.  */
diff --git a/nptl_db/structs.def b/nptl_db/structs.def
index f834d1d74c..a3aa71aade 100644
--- a/nptl_db/structs.def
+++ b/nptl_db/structs.def
@@ -110,7 +110,7 @@ DB_RTLD_GLOBAL_FIELD (dl_tls_dtv_slotinfo_list)
 DB_STRUCT (dtv_slotinfo_list)
 DB_STRUCT_FIELD (dtv_slotinfo_list, len)
 DB_STRUCT_FIELD (dtv_slotinfo_list, next)
-DB_STRUCT_ARRAY_FIELD (dtv_slotinfo_list, slotinfo)
+DB_STRUCT_FLEXIBLE_ARRAY (dtv_slotinfo_list, slotinfo)
 
 DB_STRUCT (dtv_slotinfo)
 DB_STRUCT_FIELD (dtv_slotinfo, gen)
diff --git a/nptl_db/thread_dbP.h b/nptl_db/thread_dbP.h
index 1dbb543d83..cf6a2b0221 100644
--- a/nptl_db/thread_dbP.h
+++ b/nptl_db/thread_dbP.h
@@ -37,12 +37,14 @@ enum
   {
 # define DB_STRUCT(type)		SYM_SIZEOF_##type,
 # define DB_STRUCT_FIELD(type, field)	SYM_##type##_FIELD_##field,
+# define DB_STRUCT_FLEXIBLE_ARRAY(type, field) DB_STRUCT_FIELD (type, field)
 # define DB_SYMBOL(name)		SYM_##name,
 # define DB_FUNCTION(name)		SYM_##name,
 # define DB_VARIABLE(name)		SYM_##name, SYM_DESC_##name,
 # include "structs.def"
 # undef DB_STRUCT
 # undef DB_STRUCT_FIELD
+# undef DB_STRUCT_FLEXIBLE_ARRAY
 # undef DB_SYMBOL
 # undef DB_FUNCTION
 # undef DB_VARIABLE
@@ -90,6 +92,7 @@ struct td_thragent
   uint32_t ta_sizeof_##type;
 # define DB_STRUCT_FIELD(type, field) \
   db_desc_t ta_field_##type##_##field;
+# define DB_STRUCT_FLEXIBLE_ARRAY(type, field) DB_STRUCT_FIELD (type, field)
 # define DB_SYMBOL(name) \
   psaddr_t ta_addr_##name;
 # define DB_FUNCTION(name) \
@@ -100,6 +103,7 @@ struct td_thragent
 # include "structs.def"
 # undef DB_STRUCT
 # undef DB_STRUCT_FIELD
+# undef DB_STRUCT_FLEXIBLE_ARRAY
 # undef DB_FUNCTION
 # undef DB_SYMBOL
 # undef DB_VARIABLE