Re: Lua VM Exception Handling
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- Subject: Re: Lua VM Exception Handling
- From: Mark Hamburg <mhamburg@...>
- Date: 2006年7月01日 11:08:05 -0700
You can also provide an explicit free operation to handle the
non-exceptional case.
Here's a rough outline of how one might handle this...
Foo** fooHdl = lua_newuserdata( L, sizeof( Foo* ) );
/* Push a proxy to hold the foo object. */
pushFooMetatable( L );
/* Push the metatable containing the GC metamethod. */
lua_setmetatable( L, -2 );
/* Set the metatable. */
*fooHdl = FooLib_alloc();
/* Allocate the foo. */
/* Process the data, allocate return results in Lua, etc. */
/* Success. Clean up fast. */
Foo* foo = *fooHdl;
*fooHdl = NULL;
FooLib_free( foo );
The GC metamethod for Foo userdatas will check first for NULL before calling
FooLib_free.
Mark
on 7/1/06 8:20 AM, Matt Campbell at mattc@freedombox.cc wrote:
> Hello Andrew:
>
> The correct solution is to wrap the library-allocated data in a
> userdatum whose __gc metamethod frees the data. This way, the data is
> under the control of the Lua garbage collector. Then you no longer have
> to explicitly free it at the end of your C function; just make sure the
> userdatum stays on the Lua stack. And you'll know that the data will
> always eventually be freed when it's no longer needed, even if a Lua
> error occurred. For more information, see the chapter on managing
> resources in the book _Programming in Lua_, the first edition of which
> is available at no charge online.