Error in JNI method code

Question

can anybody tell me the errors in this code.
JNIEXPORT jstring JNICALL Java_TestParams_replicate
(JNIEnv * env, jobject obj, jstring s)
const char s2, s2_copy, *s3;
jboolean copy;
jstring s4;
copy = JNI_TRUE;
s2 = (*env)->GetStringUTFChars (env, s, & copy);
s2_copy = (*env)->GetStringUTFChars (env, s, & copy);
printf ("Inside C: replicate String = %s\n", s2);
s3 = strcat (s2, s2_copy);
s4 = (*env)->NewStringUTF (env, s2);
printf ("Inside C: replicate return value = %s\n", s3);
return s4;
when i am trying to compile the above code i am getting the warning like this
test_params.c: In function ?Java_TestParams_replicate?:
test_params.c:34: warning: passing argument 1 of ?strcat? discards qualifiers from pointer target type
thanks
str

Answer 1

Well, first of all you should not cat or copy into memory specified as "const".
Second - NEVER copy or cat data to memory (pointed by s2 in your case) if you have no info about buffer length. 99% your code will cause illegal memory access error.