vim-patch:8.2.0233: crash when using garbagecollect() in between rand()

Problem:    Crash when using garbagecollect() in between rand().
Solution:   Redesign the rand() and srand() implementation. (Yasuhiro
            Matsumoto, closes vim/vim#5587, closes vim/vim#5588)
https://github.com/vim/vim/commit/4f645c54efe33d7a11e314676e503118761f08a7

Omit test_srand_seed.
Unmacroify SHUFFLE_XOSHIRO128STARSTAR and SPLITMIX32 while we're at it (leave
ROTL alone as it's fairly innocent).

3 files changed, 142 insertions, 112 deletions

diff --git a/runtime/doc/vim_diff.txt b/runtime/doc/vim_diff.txt
index 7e61eac404..11849632c5 100644
--- a/runtime/doc/vim_diff.txt
+++ b/runtime/doc/vim_diff.txt
@@ -574,6 +574,7 @@ Test functions:
   test_scrollbar()
   test_setmouse()
   test_settime()
+  test_srand_seed()
 
 TUI:
 			  *t_xx* *termcap-options* *t_AB* *t_Sb* *t_vb* *t_SI*
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 39cbb4823a..b96ff50787 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -6979,73 +6979,129 @@ static void f_py3eval(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   script_host_eval("python3", argvars, rettv);
 }
 
+static void init_srand(uint32_t *const x)
+  FUNC_ATTR_NONNULL_ALL
+{
+#ifndef MSWIN
+  static int dev_urandom_state = NOTDONE;  // FAIL or OK once tried
+
+  if (dev_urandom_state != FAIL) {
+    const int fd = os_open("/dev/urandom", O_RDONLY, 0);
+    struct {
+      union {
+        uint32_t number;
+        char bytes[sizeof(uint32_t)];
+      } contents;
+    } buf;
+
+    // Attempt reading /dev/urandom.
+    if (fd == -1) {
+      dev_urandom_state = FAIL;
+    } else {
+      buf.contents.number = 0;
+      if (read(fd, buf.contents.bytes, sizeof(uint32_t)) != sizeof(uint32_t)) {
+        dev_urandom_state = FAIL;
+      } else {
+        dev_urandom_state = OK;
+        *x = buf.contents.number;
+      }
+      os_close(fd);
+    }
+  }
+  if (dev_urandom_state != OK) {
+    // Reading /dev/urandom doesn't work, fall back to time().
+#endif
+    *x = time(NULL);
+#ifndef MSWIN
+  }
+#endif
+}
+
+static inline uint32_t splitmix32(uint32_t *const x)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_ALWAYS_INLINE
+{
+  uint32_t z = (*x += 0x9e3779b9);
+  z = (z ^ (z >> 16)) * 0x85ebca6b;
+  z = (z ^ (z >> 13)) * 0xc2b2ae35;
+  return z ^ (z >> 16);
+}
+
+static inline uint32_t shuffle_xoshiro128starstar(uint32_t *const x, uint32_t *const y,
+                                                  uint32_t *const z, uint32_t *const w)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_ALWAYS_INLINE
+{
+#define ROTL(x, k) ((x << k) | (x >> (32 - k)))
+  const uint32_t result = ROTL(*y * 5, 7) * 9;
+  const uint32_t t = *y << 9;
+  *z ^= *x;
+  *w ^= *y;
+  *y ^= *z;
+  *x ^= *w;
+  *z ^= t;
+  *w = ROTL(*w, 11);
+#undef ROTL
+  return result;
+}
+
 /// "rand()" function
 static void f_rand(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
-  list_T *l = NULL;
+  uint32_t result;
 
   if (argvars[0].v_type == VAR_UNKNOWN) {
-    static list_T *globl = NULL;
+    static uint32_t gx, gy, gz, gw;
+    static bool initialized = false;
 
     // When no argument is given use the global seed list.
-    if (globl == NULL) {
+    if (!initialized) {
       // Initialize the global seed list.
-      f_srand(argvars, rettv, fptr);
-      l = rettv->vval.v_list;
-      if (tv_list_len(l) != 4) {
-        tv_clear(rettv);
-        goto theend;
-      }
-      globl = l;
-    } else {
-      l = globl;
+      uint32_t x;
+      init_srand(&x);
+
+      gx = splitmix32(&x);
+      gy = splitmix32(&x);
+      gz = splitmix32(&x);
+      gw = splitmix32(&x);
+      initialized = true;
     }
+
+    result = shuffle_xoshiro128starstar(&gx, &gy, &gz, &gw);
   } else if (argvars[0].v_type == VAR_LIST) {
-    l = argvars[0].vval.v_list;
+    list_T *const l = argvars[0].vval.v_list;
     if (tv_list_len(l) != 4) {
       goto theend;
     }
-  } else {
-    goto theend;
-  }
 
-  typval_T *const tvx = TV_LIST_ITEM_TV(tv_list_find(l, 0L));
-  typval_T *const tvy = TV_LIST_ITEM_TV(tv_list_find(l, 1L));
-  typval_T *const tvz = TV_LIST_ITEM_TV(tv_list_find(l, 2L));
-  typval_T *const tvw = TV_LIST_ITEM_TV(tv_list_find(l, 3L));
-  if (tvx->v_type != VAR_NUMBER) {
-    goto theend;
-  }
-  if (tvy->v_type != VAR_NUMBER) {
-    goto theend;
-  }
-  if (tvz->v_type != VAR_NUMBER) {
-    goto theend;
-  }
-  if (tvw->v_type != VAR_NUMBER) {
-    goto theend;
-  }
-  uint32_t x = tvx->vval.v_number;
-  uint32_t y = tvy->vval.v_number;
-  uint32_t z = tvz->vval.v_number;
-  uint32_t w = tvw->vval.v_number;
+    typval_T *const tvx = TV_LIST_ITEM_TV(tv_list_find(l, 0L));
+    typval_T *const tvy = TV_LIST_ITEM_TV(tv_list_find(l, 1L));
+    typval_T *const tvz = TV_LIST_ITEM_TV(tv_list_find(l, 2L));
+    typval_T *const tvw = TV_LIST_ITEM_TV(tv_list_find(l, 3L));
+    if (tvx->v_type != VAR_NUMBER) {
+      goto theend;
+    }
+    if (tvy->v_type != VAR_NUMBER) {
+      goto theend;
+    }
+    if (tvz->v_type != VAR_NUMBER) {
+      goto theend;
+    }
+    if (tvw->v_type != VAR_NUMBER) {
+      goto theend;
+    }
+    uint32_t x = tvx->vval.v_number;
+    uint32_t y = tvy->vval.v_number;
+    uint32_t z = tvz->vval.v_number;
+    uint32_t w = tvw->vval.v_number;
 
-  // SHUFFLE_XOSHIRO128STARSTAR
-#define ROTL(x, k) ((x << k) | (x >> (32 - k)))
-  const uint32_t result = ROTL(y * 5, 7) * 9;
-  const uint32_t t = y << 9;
-  z ^= x;
-  w ^= y;
-  y ^= z;
-  x ^= w;
-  z ^= t;
-  w = ROTL(w, 11);
-#undef ROTL
+    result = shuffle_xoshiro128starstar(&x, &y, &z, &w);
 
-  tvx->vval.v_number = (varnumber_T)x;
-  tvy->vval.v_number = (varnumber_T)y;
-  tvz->vval.v_number = (varnumber_T)z;
-  tvw->vval.v_number = (varnumber_T)w;
+    tvx->vval.v_number = (varnumber_T)x;
+    tvy->vval.v_number = (varnumber_T)y;
+    tvz->vval.v_number = (varnumber_T)z;
+    tvw->vval.v_number = (varnumber_T)w;
+  } else {
+    goto theend;
+  }
 
   rettv->v_type = VAR_NUMBER;
   rettv->vval.v_number = (varnumber_T)result;
@@ -7057,6 +7113,28 @@ theend:
   rettv->vval.v_number = -1;
 }
 
+/// "srand()" function
+static void f_srand(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  uint32_t x = 0;
+
+  tv_list_alloc_ret(rettv, 4);
+  if (argvars[0].v_type == VAR_UNKNOWN) {
+    init_srand(&x);
+  } else {
+    bool error = false;
+    x = tv_get_number_chk(&argvars[0], &error);
+    if (error) {
+      return;
+    }
+  }
+
+  tv_list_append_number(rettv->vval.v_list, (varnumber_T)splitmix32(&x));
+  tv_list_append_number(rettv->vval.v_list, (varnumber_T)splitmix32(&x));
+  tv_list_append_number(rettv->vval.v_list, (varnumber_T)splitmix32(&x));
+  tv_list_append_number(rettv->vval.v_list, (varnumber_T)splitmix32(&x));
+}
+
 /// "perleval()" function
 static void f_perleval(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
@@ -10528,63 +10606,6 @@ static void f_stdpath(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
-/// "srand()" function
-static void f_srand(typval_T *argvars, typval_T *rettv, FunPtr fptr)
-{
-  static int dev_urandom_state = -1;  // FAIL or OK once tried
-  uint32_t x = 0;
-
-  tv_list_alloc_ret(rettv, 4);
-  if (argvars[0].v_type == VAR_UNKNOWN) {
-    if (dev_urandom_state != FAIL) {
-      const int fd = os_open("/dev/urandom", O_RDONLY, 0);
-      struct {
-        union {
-          uint32_t number;
-          char bytes[sizeof(uint32_t)];
-        } cont;
-      } buf;
-
-      // Attempt reading /dev/urandom.
-      if (fd == -1) {
-        dev_urandom_state = FAIL;
-      } else {
-        buf.cont.number = 0;
-        if (read(fd, buf.cont.bytes, sizeof(uint32_t)) != sizeof(uint32_t)) {
-          dev_urandom_state = FAIL;
-        } else {
-          dev_urandom_state = OK;
-          x = buf.cont.number;
-        }
-        os_close(fd);
-      }
-    }
-    if (dev_urandom_state != OK) {
-      // Reading /dev/urandom doesn't work, fall back to time().
-      x = time(NULL);
-    }
-  } else {
-    bool error = false;
-    x = tv_get_number_chk(&argvars[0], &error);
-    if (error) {
-      return;
-    }
-  }
-
-  uint32_t z;
-#define SPLITMIX32 ( \
-    z = (x += 0x9e3779b9), \
-    z = (z ^ (z >> 16)) * 0x85ebca6b, \
-    z = (z ^ (z >> 13)) * 0xc2b2ae35, \
-    z ^ (z >> 16))
-
-  tv_list_append_number(rettv->vval.v_list, (varnumber_T)SPLITMIX32);
-  tv_list_append_number(rettv->vval.v_list, (varnumber_T)SPLITMIX32);
-  tv_list_append_number(rettv->vval.v_list, (varnumber_T)SPLITMIX32);
-  tv_list_append_number(rettv->vval.v_list, (varnumber_T)SPLITMIX32);
-#undef SPLITMIX32
-}
-
 /*
  * "str2float()" function
  */
diff --git a/src/nvim/testdir/test_random.vim b/src/nvim/testdir/test_random.vim
index f953b93d51..6d3f7dcfd9 100644
--- a/src/nvim/testdir/test_random.vim
+++ b/src/nvim/testdir/test_random.vim
@@ -12,7 +12,7 @@ func Test_Rand()
   " Nvim does not support test_settime
   " call test_settime(12341234)
   let s = srand()
-  if filereadable('/dev/urandom')
+  if !has('win32') && filereadable('/dev/urandom')
     " using /dev/urandom
     call assert_notequal(s, srand())
   " else
@@ -22,9 +22,11 @@ func Test_Rand()
   "   call assert_notequal(s, srand())
   endif
 
-  call srand()
-  let v = rand()
-  call assert_notequal(v, rand())
+  " Nvim does not support test_srand_seed
+  " call test_srand_seed(123456789)
+  " call assert_equal(4284103975, rand())
+  " call assert_equal(1001954530, rand())
+  " call test_srand_seed()
 
   if has('float')
     call assert_fails('echo srand(1.2)', 'E805:')
@@ -40,4 +42,10 @@ func Test_Rand()
   " call test_settime(0)
 endfunc
 
+func Test_issue_5587()
+  call rand()
+  call garbagecollect()
+  call rand()
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab