[foreign-jextract] Function pointer typedef name clashes with existing function name

[Maurizio Cimadamore]

Hi Filip,
thanks for the report - I've filed this:

https://bugs.openjdk.java.net/browse/JDK-8261511

I believe jextract adds constants to the constant holder
sources/classes on a name-based basis. So if you happen to have two
descriptors that are required for different things (e.g. a function and
an upcall which happen to have same name), there is a chance that one
constant will be re-used for the other.

The solution is, of course, to use a more robust keying scheme when
adding constants, rather than just using the name.

Maurizio

On Wed, 2021-02-10 at 15:05 +0100, Filip Krakowski wrote:
> Hi,
> 
> I think I found another bug regarding name clashes with typedefs for 
> function pointers.
> 
> The library I use declares a function pointer within a struct's
> field 
> named "read" [1]. I think you see where this is going...
> 
>     typedef struct ucs_config_parser {
>          int                      (*read) (const char *buf, void
> *dest,
>     const void *arg);
>          int                      (*write)(char *buf, size_t max,
>                                            const void *src, const
> void
>     *arg);
>          ucs_status_t             (*clone)(const void *src, void
> *dest,
>     const void *arg);
>          void                     (*release)(void *ptr, const void
> *arg);
>          void                     (*help)(char *buf, size_t max,
> const
>     void *arg);
>          const void               *arg;
>     } ucs_config_parser_t;
> 
> 
> Since "unistd.h" also declares a "read" function [2], jextract then 
> (correctly) generates a MethodHandle for it
> but uses the wrong FunctionDescriptor belonging to ucx's "read" in
> the 
> process.
> 
>     static final FunctionDescriptor read$FUNC_ =
>     FunctionDescriptor.of(C_INT,
>              C_POINTER,
>              C_POINTER,
>              C_POINTER
>     );
> 
>     static final MethodHandle read$MH_ =
> RuntimeHelper.downcallHandle(
>              LIBRARIES, "read",
>              "(ILjdk/incubator/foreign/MemoryAddress;J)J",
>              read$FUNC_, false
>     );
> 
> 
> As you can see the generated FunctionDescriptor and the descriptor 
> string ("(ILjdk/incubator/foreign/MemoryAddress;J)J")
> do not match. On startup, I immediately get the following Exception 
> originating from the downcallHandle call.
> 
>     Caused by: java.lang.IllegalArgumentException: Carrier size
>     mismatch: int != b64[abi/kind=POINTER]
> 
> My guess is that the FunctionDescriptor is generated correctly at
> first, 
> but gets overridden once the parser reaches the
> function pointer declared within the struct in [1].
> 
> 
> Best regards
> Filip
> 
> [1] 
> https://github.com/openucx/ucx/blob/16ad2cc56b6c63a0fdc39bac3dce03463d6d137f/src/ucs/config/parser.h#L40-L48
> [2] https://linux.die.net/man/2/read