Re: FYI: Linker & Verifier fixes

[Bryce McKinlay <mckinlay at redhat dot com>]

Hi Robert,

I believe there is still a bug here with the String being passed to 
ffi_prep_closure:

+          // Initializes the cif and the closure. If that worked the 
closure is
+          // stored as a function pointer in the atable.
+          if ( ffi_prep_cif(cif, FFI_DEFAULT_ABI, 1,
+                            &ffi_type_void, arg_types) == FFI_OK
+               && (ffi_prep_closure
+                   (closure, cif,
+                   _Jv_ThrowNoClassDefFoundErrorTrampoline,
+                   (void *) _Jv_NewStringUtf8Const(sym.class_name))
+                   == FFI_OK))

The String returned by _Jv_NewStringUtf8Const(sym.class_name) is 
allocated by the GC, but there is no pointer to this string that is 
visible to the GC, so it is at risk of being prematurely collected. (The 
closure data itself will not be visible to the GC as it will not scan 
malloc()'ed memory).

A simple solution would be to add the Strings as keys in a HashMap each 
time a closure is created.

Bryce


Robert Schuster wrote:
> Hi,
> I apply the following patch with this ChangeLog. I tested it on
> i686-pc-linux-gnu and there where no regressions.
>
> However since this introduces a memory leak I will file a PR about this.
>
> 2006-02-01  Robert Schuster  <robertschuster@fsfe.org>
>
> 	* link.cc:
> 	(_Jv_Linker::find_field_helper): Added checks.
> 	(_Jv_Linker::find_field): Use exception swallowing class resolution
> 	and added early return.
> 	(_Jv_ThrowNoClassDefFoundErrorTrampoline): New function.
> 	(_Jv_Linker::link_symbol_table):  Use exception swallowing class
> 	resolution, added ffi_closure installation routine, use
> 	_Jv_ThrowNoClassDefFoundError for missing static method.
> 	(_Jv_Linker::ensure_class_linked): Added string check which does
> 	not trigger class resolution.
> 	* java/lang/natClassLoader.cc:
> 	(_Jv_FindClassNoException): New method.
> 	* java/lang/Class.h:
> 	(_Jv_FindClassNoException): New method declaration.
> 	* include/jvm.h:
> 	(_Jv_FindClassNoException): New method declaration.
> 	(_Jv_FindClassFromSignatureNoException): New method declaration.
> 	* prims.cc:
> 	(_Jv_FindClassFromSignatureNoException): New method.
>         * gcj/javaprims.h:
>         (_Jv_equalsUtf8Classname): New method declaration.
>         (_Jv_isPrimitiveOrDerived): Dito.
>         * prims.cc:
> 	(_Jv_equalsUtf8Classnames): New method.
>         (_Jv_isPrimitiveOrDerived): New method.
>         * verify.cc:
>         (ref_intersection::equals): Use new classname comparison method.
>         (type::compatible): Use new classname comparison method. Added
>         check whether LHS' type is java.lang.Object .
>         (type::resolve): Added new optional debug message and simplified
>         if-expression.
>         (type::to_array): Added codepath that generates an array type
>         without resolving the element type.
>
> cya
> Robert