[foreign-jextract] jextract-generated MethodHandle is null

[Filip Krakowski]

Hi,

Got to the bottom of this. "ibv_post_send" is an inline function 
declared in the "verbs.h" header file 
(https://github.com/linux-rdma/rdma-core/blob/master/libibverbs/verbs.h#L3222-L3226). 
Many other functions are also declared inline within this header file. 
Inline functions will most likely never be supported, right?

Best regards
Filip

On 18.09.20 21:44, Filip Krakowski wrote:
> Hi,
>
> please ignore the last mail. Just tried looking up the symbol manually 
> using LibraryLookup which resulted in an Exception.
> For some strange reason the symbol "ibv_post_send" is indeed missing 
> within the shared library.
>
>    nm -D libibverbs.so | grep send
>
>    0000000000007f70 T ibv_cmd_post_send
>                      U nl_send_auto
>                      U nl_send_simple
>                      U sendto
>
>
> Best regards,
> Filip
>
> On 18.09.20 21:23, Filip Krakowski wrote:
>> Hi,
>>
>> I had some time to code again and found the following bug in 
>> jextract. Since jextract's source mode is not working at the moment 
>> (https://bugs.openjdk.java.net/browse/JDK-8252799) I switched to 
>> class file mode. The following code (only the important parts) was 
>> generated using source mode for better explanation.
>>
>>    static final FunctionDescriptor ibv_post_send$FUNC_ 
>> =FunctionDescriptor.of(C_INT,
>>         C_POINTER,
>>         C_POINTER,
>>         C_POINTER );
>>
>>    static final MethodHandle ibv_post_send$MH_ 
>> =RuntimeHelper.downcallHandle(
>>         LIBRARIES,"ibv_post_send",
>> "(Ljdk/incubator/foreign/MemoryAddress;Ljdk/incubator/foreign/MemoryAddress;Ljdk/incubator/foreign/MemoryAddress;)I", 
>>
>>         ibv_post_send$FUNC_,false );
>>
>>    public static java.lang.invoke.MethodHandle ibv_post_send$MH() 
>> {return ibv_post_send$MH_; }
>>
>>    public static MethodHandle ibv_post_send$MH() {
>>         return header_h$constants$0.ibv_post_send$MH();
>>    }
>>
>>    public static @C("int")int ibv_post_send (@C("struct 
>> ibv_qp*")Addressable qp, at C("struct ibv_send_wr*")Addressable 
>> wr, at C("struct ibv_send_wr**")Addressable bad_wr) {
>>         try {
>>             return 
>> (int)header_h$constants$0.ibv_post_send$MH().invokeExact(qp.address(), 
>> wr.address(), bad_wr.address());
>>         }catch (Throwable ex) {
>>             throw new AssertionError(ex);
>>         }
>>    }
>>
>> Calling the generated "ibv_post_send" 
>> (https://linux.die.net/man/3/ibv_post_send) method results in a 
>> NullPointerException since RuntimeHelper#downcallHandle returns null 
>> instead the correct MethodHandle.
>>
>>    /java.lang.AssertionError: java.lang.NullPointerException: Cannot
>>    invoke
>> "java.lang.invoke.MethodHandle.invokeExact(jdk.incubator.foreign.MemoryAddress, 
>>
>>    jdk.incubator.foreign.MemoryAddress,
>>    jdk.incubator.foreign.MemoryAddress)" because the return value of
>>    "org.linux.rdma.header_h$constants$0.ibv_post_send$MH()" is null/
>>
>> I also tried creating my own MethodHandle using 
>> RuntimeHelper#downcallHandle which also returned null. Interestingly, 
>> all previous calls to methods from the same shared library work 
>> without problems.
>>
>> Best regards,
>> Filip
>