From 85a3c1699c9587a9e952b4ab75b1c6c310ebebea Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 9 Jul 2025 14:40:36 -0300
Subject: New method to unload DLLs

External strings created by DLLs may need the DLL code to be
deallocated. This implies that a DLL can only be unloaded after all
its strings were deallocated, which happen only after the run of all
finalizers. To ensure that order, we create a 'library string' to
represent each DLL and keep it locked. When this string is deallocated
(after the deallocation of any string created by the DLL) it closes its
corresponding DLL.
---
 testes/attrib.lua   |  8 +++++++-
 testes/libs/lib22.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

(limited to 'testes')

diff --git a/testes/attrib.lua b/testes/attrib.lua
index d8b6e0f3..8a3462ea 100644
--- a/testes/attrib.lua
+++ b/testes/attrib.lua
@@ -300,6 +300,12 @@ else
   assert(_ENV.x == "lib2-v2" and _ENV.y == DC"lib2-v2")
   assert(lib2.id("x") == true)   -- a different "id" implementation
 
+  for _, len in ipairs{0, 10, 39, 40, 41, 1000} do
+    local str = string.rep("a", len)
+    local str1 = lib2.newstr(str)
+    assert(str == str1)
+  end
+
   -- test C submodules
   local fs, ext = require"lib1.sub"
   assert(_ENV.x == "lib1.sub" and _ENV.y == DC"lib1")
@@ -447,7 +453,7 @@ do
 end
 
 
--- test of large float/integer indices 
+-- test of large float/integer indices
 
 -- compute maximum integer where all bits fit in a float
 local maxint = math.maxinteger
diff --git a/testes/libs/lib22.c b/testes/libs/lib22.c
index 8e656502..b377cce5 100644
--- a/testes/libs/lib22.c
+++ b/testes/libs/lib22.c
@@ -1,3 +1,7 @@
+/* implementation for lib2-v2 */
+
+#include <string.h>
+
 #include "lua.h"
 #include "lauxlib.h"
 
@@ -8,8 +12,54 @@ static int id (lua_State *L) {
 }
 
 
+struct STR {
+  void *ud;
+  lua_Alloc allocf;
+};
+
+
+static void *t_freestr (void *ud, void *ptr, size_t osize, size_t nsize) {
+  struct STR *blk = (struct STR*)ptr - 1;
+  blk->allocf(blk->ud, blk, sizeof(struct STR) + osize, 0);
+  return NULL;
+}
+
+
+static int newstr (lua_State *L) {
+  size_t len;
+  const char *str = luaL_checklstring(L, 1, &len);
+  void *ud;
+  lua_Alloc allocf = lua_getallocf(L, &ud);
+  struct STR *blk = (struct STR*)allocf(ud, NULL, 0,
+                                        len + 1 + sizeof(struct STR));
+  if (blk == NULL) {  /* allocation error? */
+    lua_pushliteral(L, "not enough memory");
+    lua_error(L);  /* raise a memory error */
+  }
+  blk->ud = ud;  blk->allocf = allocf;
+  memcpy(blk + 1, str, len + 1);
+  lua_pushexternalstring(L, (char *)(blk + 1), len, t_freestr, L);
+  return 1;
+}
+
+
+/*
+** Create an external string and keep it in the registry, so that it
+** will test that the library code is still available (to deallocate
+** this string) when closing the state.
+*/
+static void initstr (lua_State *L) {
+  lua_pushcfunction(L, newstr);
+  lua_pushstring(L,
+     "012345678901234567890123456789012345678901234567890123456789");
+  lua_call(L, 1, 1);  /* call newstr("0123...") */
+  luaL_ref(L, LUA_REGISTRYINDEX);  /* keep string in the registry */
+}
+
+
 static const struct luaL_Reg funcs[] = {
   {"id", id},
+  {"newstr", newstr},
   {NULL, NULL}
 };
 
@@ -18,6 +68,7 @@ LUAMOD_API int luaopen_lib2 (lua_State *L) {
   lua_settop(L, 2);
   lua_setglobal(L, "y");  /* y gets 2nd parameter */
   lua_setglobal(L, "x");  /* x gets 1st parameter */
+  initstr(L);
   luaL_newlib(L, funcs);
   return 1;
 }
-- 
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