8252051: Make mlvmJvmtiUtils strncpy uses GCC 10.x friendly

Reviewed-by: phh

test/hotspot/jtreg/vmTestbase/vm/mlvm/share/mlvmJvmtiUtils.c

@@ -45,11 +45,6 @@ void copyFromJString(JNIEnv * pEnv, jstring src, char ** dst) {
     NSK_CPP_STUB3(ReleaseStringUTFChars, pEnv, src, pStr);
 }
 
-#if !defined(__clang_major__) && defined(__GNUC__) && (__GNUC__ >= 8)
-_Pragma("GCC diagnostic push")
-_Pragma("GCC diagnostic ignored \"-Wstringop-truncation\"")
-#endif
-
 struct MethodName * getMethodName(jvmtiEnv * pJvmtiEnv, jmethodID method) {
     char * szName;
     char * szSignature;
@@ -71,18 +66,16 @@ struct MethodName * getMethodName(jvmtiEnv * pJvmtiEnv, jmethodID method) {
     }
 
     mn = malloc(sizeof(MethodNameStruct));
-    strncpy(mn->methodName, szName, sizeof(mn->methodName));
-    strncpy(mn->classSig, szSignature, sizeof(mn->classSig));
+    strncpy(mn->methodName, szName, sizeof(mn->methodName) - 1);
+    mn->methodName[sizeof(mn->methodName) - 1] = '\0';
+    strncpy(mn->classSig, szSignature, sizeof(mn->classSig) - 1);
+    mn->classSig[sizeof(mn->classSig) - 1] = '\0';
 
     NSK_JVMTI_VERIFY(NSK_CPP_STUB2(Deallocate, pJvmtiEnv, (void *) szName));
     NSK_JVMTI_VERIFY(NSK_CPP_STUB2(Deallocate, pJvmtiEnv, (void *) szSignature));
     return mn;
 }
 
-#if !defined(__clang_major__) && defined(__GNUC__) && (__GNUC__ >= 8)
-_Pragma("GCC diagnostic pop")
-#endif
-
 char * locationToString(jvmtiEnv * pJvmtiEnv, jmethodID method, jlocation location) {
     struct MethodName * pMN;
     // gcc 7.3 claims that snprintf below can output between 6 and 531 bytes. Setting buffer size to 600.