Merge branch 'bugfix/dont_use_flexible_arr_in_union' into 'master'

fix(bluedroid): removed the code relying on compiler-specific extension for FAM in union

Closes BT-4126

See merge request espressif/esp-idf!42236

Author: Jiang Jiang Jian

components/bt/host/bluedroid/stack/include/stack/sdp_api.h

@@ -96,8 +96,8 @@ typedef struct {
         UINT8       u8;                         /* 8-bit integer            */
         UINT16      u16;                        /* 16-bit integer           */
         UINT32      u32;                        /* 32-bit integer           */
+        UINT8       array[4];                   /* Variable length field    */
         struct t_sdp_disc_attr *p_sub_attr;     /* Addr of first sub-attr (list)*/
-        UINT8       array[];                    /* Variable length field    */
     } v;
 
 } tSDP_DISC_ATVAL;

components/bt/host/bluedroid/stack/sdp/sdp_utils.c

@@ -785,6 +785,14 @@ BOOLEAN sdpu_compare_uuid_with_attr (tBT_UUID *p_btuuid, tSDP_DISC_ATTR *p_attr)
     } else if (p_btuuid->len == LEN_UUID_32) {
         return (BOOLEAN)(p_btuuid->uu.uuid32 == p_attr->attr_value.v.u32);
     }
+    /* coverity[overrun-buffer-arg] */
+    /*
+       Event overrun-buffer-arg: Overrun of static array "&p_attr->attr_value.v.array" of size 4 bytes by passing it to a function which indexes it with argument "16U" at byte position 15
+       FALSE-POSITIVE error from Coverity test tool. Please do NOT remove following comment.
+       False-positive: SDP uses scratch buffer to hold the attribute value.
+       The actual size of tSDP_DISC_ATVAL does not matter.
+       If the array size in tSDP_DISC_ATVAL is increase, we would increase the system RAM usage unnecessarily
+    */
     else if (p_btuuid->len == LEN_UUID_128) {
         return (BOOLEAN)(!memcmp(p_btuuid->uu.uuid128, (void *) p_attr->attr_value.v.array, LEN_UUID_128));
     }