Describe the Issue

When i pass a struct to c function @cstruct annotated interface it's values are garbage

Using the latest version of GraalVM can resolve many issues.

• I tried with the latest version of GraalVM.

GraalVM Version

java version "24" 2025-03-18
Java(TM) SE Runtime Environment Oracle GraalVM 24+36.1 (build 24+36-jvmci-b01)
Java HotSpot(TM) 64-Bit Server VM Oracle GraalVM 24+36.1 (build 24+36-jvmci-b01, mixed mode, sharing)

Operating System and Version

Linux fedora 6.14.3-300.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Apr 20 16:08:39 UTC 2025 x86_64 GNU/Linux

Troubleshooting Confirmation

• I tried the suggestions in the troubleshooting guide.

Run Command

native-image -cp . -H:CLibraryPath=$(pwd) -H:IncludeResources=add.h --native-compiler-options="-I$(pwd)" -Ob -jar Main.jar

Expected Behavior

5
Age: 5

Actual Behavior

5
Age: -678812048

Steps to Reproduce

1.create a c function which takes a struct as param
2. pass the struct obj from java
3. print the properties in c and java

Additional Context

java code:

import org.graalvm.nativeimage.c.CContext;
import org.graalvm.nativeimage.c.struct.CField;
import org.graalvm.nativeimage.c.struct.CStruct;
import org.graalvm.word.PointerBase;

@CStruct("User")
@CContext(Main.Directives.class)
public interface User extends PointerBase {

    @CField("age")
    int age();

    @CField("age")
    void age(int age);

}

 User u = StackValue.get(User.class);

u.age(5);
System.out.println(u.age());

print_user(u);

C code:

void print_user(User u) {
    printf("Age: %d", u.age);
}

Run-Time Log Output and Error Messages

No response