RFR: 8214776: Avoid GCC 8.X strncpy() errors in JFR code

[Simon Tooke]

On 2018-12-11 8:47 a.m., Severin Gehwolf wrote:
> Hi Simon,
>
> On Mon, 2018-12-10 at 10:25 -0500, Simon Tooke wrote:
>> This small patch fixes some simple warnings in JFR code, found by GCC 8.1
>> Essentially, any code sequence of the pattern
>>
>>     int l = strlen(somestring)
>>     char* buffer = malloc(l + 1)
>>     strncpy(buffer, somestring, l)
>>     buffer[l] = 0
>>
>> is replaced by
>>
>>     int len = strlen(somestring)
>>     char* buffer = malloc(len + 1)
>>     strncpy(buffer, somestring, len + 1)
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8214776
>> Webrev:
>> http://cr.openjdk.java.net/~sgehwolf/webrevs/stooke/JDK-8214776/02/webrev/
> Shouldn't these:
>
> @@ -332,7 +331,7 @@
>      if (NULL == emergency_dump_path) {
>        return NULL;
>      }
> -    strncpy(emergency_dump_path, buffer, emergency_filename_length);
> +    strncpy(emergency_dump_path, buffer, emergency_filename_length + 1);
>      emergency_dump_path[emergency_filename_length] = '\0';
>    }
>    return emergency_dump_path;
> @@ -407,7 +406,7 @@
>    if (_path == NULL) {
>      return false;
>    }
> -  strncpy(_path, path, path_len);
> +  strncpy(_path, path, path_len + 1);
>    _path[path_len] = '\0';
>
> Be this instead?
>
> @@ -332,8 +331,7 @@
>      if (NULL == emergency_dump_path) {
>        return NULL;
>      }
> -    strncpy(emergency_dump_path, buffer, emergency_filename_length);
> -    emergency_dump_path[emergency_filename_length] = '\0';
> +    strncpy(emergency_dump_path, buffer, emergency_filename_length + 1);
>    }
>    return emergency_dump_path;
>  }
> @@ -407,8 +405,7 @@
>    if (_path == NULL) {
>      return false;
>    }
> -  strncpy(_path, path, path_len);
> -  _path[path_len] = '\0';
> +  strncpy(_path, path, path_len + 1);
Yes, you're absolutely right - the null terminator is now set in the
line before.
I can produce a new webrev.

>
> Thanks,
> Severin
>
Thank you,
-Simon