bugfix: jit.prngstate() did not allow integer arg which broke backward compatibility.

Author: xiaocang

README.md

@@ -153,11 +153,20 @@ When the `state` argument is non-nil, it is expected to be an array of up to 8
 unsigned Lua numbers, each with value less than 2\*\*32-1. This will set the
 current PRNG state and return the state that was overridden.
 
+**Note:** For backward compatibility, `state` argument can also be an unsigned
+Lua number less than 2\*\*32-1.
+
+**Note:** When the `state` argument is an array and less than 8 numbers, or the
+`state` is a number, the remaining positions are filled with zeros.
+
 Usage:
 
 ```lua
 local state = jit.prngstate()
 local oldstate = jit.prngstate{ a, b, c, ... }
+
+jit.prngstate(32) -- {32, 0, 0, 0, 0, 0, 0, 0}
+jit.prngstate{432, 23, 50} -- {432, 23, 50, 0, 0, 0, 0, 0}
 ```
 
 **Note:** This API has no effect if LuaJIT is compiled with

src/lib_jit.c

@@ -164,28 +164,38 @@ LJLIB_CF(jit_prngstate)
 
   /* We need to set new state using the input array. */
   if (L->base < L->top && !tvisnil(L->base)) {
-    GCtab *t = lj_lib_checktab(L, 1);
     PRNGState prng;
-    int i = 1, len = lj_tab_len(t);
+    if (tvisnumber(L->base)) {
+      TValue *o = L->base;
 
-    /* The input array must have at most 8 elements. */
-    if (len > 8)
-      lj_err_arg(L, 1, LJ_ERR_PRNGSTATE);
+      if (!tvisint(o) && ((double)(uint32_t)numV(o) != numV(o)))
+        lj_err_arg(L, 1, LJ_ERR_PRNGSTATE);
 
-    for (i = 1; i <= len; i++) {
-      cTValue *v = lj_tab_getint(t, i);
+      prng.u[0] = numberVint(o);
+      for (i = 1; i < 4; i++)
+        prng.u[i] = 0;
+    } else {
+      GCtab *t = lj_lib_checktab(L, 1);
+      int i = 1, len = lj_tab_len(t);
 
-      if (!tvisint(v) && (!tvisnum(v) || (double)(uint32_t)numV(v) != numV(v)))
+      /* The input array must have at most 8 elements. */
+      if (len > 8)
         lj_err_arg(L, 1, LJ_ERR_PRNGSTATE);
 
-      if (i & 1)
-	prng.u[(i-1)/2] = numberVint(v);
-      else
-	prng.u[(i-1)/2] = prng.u[(i-1)/2] | ((uint64_t)numberVint(v) << 32);
-    }
+      for (i = 1; i <= len; i++) {
+        cTValue *v = lj_tab_getint(t, i);
+
+        if (!tvisint(v) && (!tvisnum(v) || (double)(uint32_t)numV(v) != numV(v)))
+          lj_err_arg(L, 1, LJ_ERR_PRNGSTATE);
 
-    for (i /= 2; i < 4; i++)
-      prng.u[i] = 0;
+        if (i & 1)
+          prng.u[(i-1)/2] = numberVint(v);
+        else
+          prng.u[(i-1)/2] = prng.u[(i-1)/2] | ((uint64_t)numberVint(v) << 32);
+      }
+      for (i /= 2; i < 4; i++)
+        prng.u[i] = 0;
+    }
 
     /* Re-initialize the JIT prng. */
     J->prng = prng;

src/lj_errmsg.h

@@ -108,7 +108,8 @@ ERRDEF(NOJIT,	"no JIT compiler for this architecture (yet)")
 ERRDEF(NOJIT,	"JIT compiler permanently disabled by build option")
 #endif
 ERRDEF(JITOPT,	"unknown or malformed optimization flag " LUA_QS)
-ERRDEF(PRNGSTATE,	"PRNG state must be an array with up to 8 integers")
+ERRDEF(PRNGSTATE,     "PRNG state must be an array with up to 8 integers "
+                  "or an integer")
 
 /* Lexer/parser errors. */
 ERRDEF(XMODE,	"attempt to load chunk with wrong mode")

t/prngstate.t

@@ -32,7 +32,7 @@ print_array(jit.prngstate({423,432,432,423,56,867,35,5347,452}))
 423 432 432 423 56 867 35 5347
 --- jv
 --- err
-bad argument #1 to 'prngstate' (PRNG state must be an array with up to 8 integers)
+bad argument #1 to 'prngstate' (PRNG state must be an array with up to 8 integers or an integer)
 --- exit: 1
 
 
@@ -50,3 +50,27 @@ ok
 --- jv
 --- err eval
 qr/trace too short at jit\.prngstate/
+
+
+
+=== TEST 3: PRNG state can be an integer
+--- lua
+function print_array(a)
+  local out = a[1]
+  for i=2,#a do
+    out = out.." "..tostring(a[i])
+  end
+  print(out)
+end
+
+jit.prngstate(0)
+print_array(jit.prngstate(30))
+print_array(jit.prngstate(32))
+print_array(jit.prngstate(4294967296)) -- 2 ** 32
+--- out
+0 0 0 0 0 0 0 0
+30 0 0 0 0 0 0 0
+--- jv
+--- err
+bad argument #1 to 'prngstate' (PRNG state must be an array with up to 8 integers or an integer)
+--- exit: 1