lua: add flex array field to TString type

module/lua/lobject.h

@@ -404,19 +404,22 @@ typedef TValue *StkId;  /* index to stack elements */
 /*
 ** Header for string value; string bytes follow the end of this structure
 */
-typedef union TString {
-  L_Umaxalign dummy;  /* ensures maximum alignment for strings */
-  struct {
-    CommonHeader;
-    lu_byte extra;  /* reserved words for short strings; "has hash" for longs */
-    unsigned int hash;
-    size_t len;  /* number of characters in string */
-  } tsv;
+typedef struct TString {
+  union {
+    L_Umaxalign dummy;  /* ensures maximum alignment for strings */
+    struct {
+      CommonHeader;
+      lu_byte extra;  /* reserved words for short strings; "has hash" for longs */
+      unsigned int hash;
+      size_t len;  /* number of characters in string */
+    } tsv;
+  };
+  char contents[];
 } TString;
 
 
 /* get the actual string (array of bytes) from a TString */
-#define getstr(ts)	cast(const char *, (ts) + 1)
+#define getstr(ts)	((ts)->contents)
 
 /* get the actual string (array of bytes) from a Lua value */
 #define svalue(o)       getstr(rawtsvalue(o))

module/lua/lstate.h

@@ -185,7 +185,7 @@ struct lua_State {
 */
 union GCObject {
   GCheader gch;  /* common header */
-  union TString ts;
+  struct TString ts;
   union Udata u;
   union Closure cl;
   struct Table h;

module/lua/lstring.c

@@ -103,7 +103,7 @@ static TString *createstrobj (lua_State *L, const char *str, size_t l,
   ts->tsv.len = l;
   ts->tsv.hash = h;
   ts->tsv.extra = 0;
-  sbuf = (char *)(TString *)(ts + 1);
+  sbuf = ts->contents;
   memcpy(sbuf, str, l*sizeof(char));
   sbuf[l] = '\0';  /* ending 0 */
   return ts;

module/lua/lstring.h

@@ -12,7 +12,7 @@
 #include "lstate.h"
 
 
-#define sizestring(s)	(sizeof(union TString)+((s)->len+1)*sizeof(char))
+#define sizestring(s)	(sizeof(struct TString)+((s)->len+1)*sizeof(char))
 
 #define sizeudata(u)	(sizeof(union Udata)+(u)->len)