From: Peter van Dijk <peter.van.dijk@powerdns.com>
Date: Thu, 11 Mar 2021 13:31:14 +0000 (+0100)
Subject: lua: don't destroy keys during table iteration
X-Git-Tag: dnsdist-1.6.0-rc1~17^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a6fb00c9df403ecc94d385d1637b9dcfb4807e9a;p=thirdparty%2Fpdns.git

lua: don't destroy keys during table iteration

via https://github.com/ahupowerdns/luawrapper/pull/38
---

diff --git a/ext/luawrapper/include/LuaContext.hpp b/ext/luawrapper/include/LuaContext.hpp
index fa2ff91bf2..49aed17bbf 100644
--- a/ext/luawrapper/include/LuaContext.hpp
+++ b/ext/luawrapper/include/LuaContext.hpp
@@ -2681,11 +2681,21 @@ struct LuaContext::Reader<std::string>
     static auto read(lua_State* state, int index)
         -> boost::optional<std::string>
     {
+        std::string result;
+
+        // lua_tolstring might convert the variable that would confuse lua_next, so we
+        //   make a copy of the variable.
+        lua_pushvalue(state, index);
+
         size_t len;
-        const auto val = lua_tolstring(state, index, &len);
-        if (val == 0)
-            return boost::none;
-        return std::string(val, len);
+        const auto val = lua_tolstring(state, -1, &len);
+
+        if (val != 0)
+          result.assign(val, len);
+
+        lua_pop(state, 1);
+
+        return val != 0 ? boost::optional<std::string>{ std::move(result) } : boost::none;
     }
 };