RFR [XS]: 8235489: handle return values of sscanf calls in hotspot

[Kim Barrett]

> On Dec 9, 2019, at 3:30 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
>> On Dec 9, 2019, at 6:22 AM, Baesken, Matthias <matthias.baesken at sap.com> wrote:
>> 
>> Hi Kim,  new webrev :
>> 
>> http://cr.openjdk.java.net/~mbaesken/webrevs/8235489.2/
>> 
>> 
>> regarding the initialization of "name"  - this is indeed for   lines  without  a name entry -  those lines exist  in /proc/self/maps .
>> I adjusted the initialization following your recommendation ( handle  matches == 6).
>> 
>> I also changed the unadorned "%s to one with an int-stringsize-parameter .
> 
> ------------------------------------------------------------------------------
> src/hotspot/os/linux/os_linux.cpp
> 2084       char name[4097]; // was PATH_MAX + 1
> 
> Please stay with the original, using PATH_MAX + 1.  I'm assuming this
> change was so in the string parsing argument you could use "%4096s" to
> limit the amount of data read into name.  That can still be done with
> the size of name being based on PATH_MAX by using a variable field
> width for the string conversion, e.g. "%*s" with an argument of
> PATH_MAX for the ("*") field width, before the name argument.
> 
> ------------------------------------------------------------------------------

Never mind.  I forgot that the scanf family interprets “%*” as “assignment-suppression”.

I think a better approach is to use a “%n” specifier to capture the number of characters
consumed thus far, in an int variable.  Something like (untested)

  int name_index;
  const char* name;
  matches = sscanf(line, “… %n”, …, &name_index);
  if (matches != 6) continue;
  name = &line[name_index];