Change non-manageable JVM option in runtime

vmoption.c

#include <jvmti.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

JNIEXPORT jint JNICALL
Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
    if (options != NULL) {
        int* addr = (int*)strtol(options, NULL, 0);
        printf("vmoption [%p] = %d\n", addr, *addr); fflush(stdout);

        const char* eq = strchr(options, '=');
        if (eq != NULL) {
            int val = atoi(eq + 1);
            *addr = val;
            printf("vmoption [%p] := %d\n", addr, val); fflush(stdout);
        }
    }

    return 0;
}