[14] RFR(S): 8234583: PrintAssemblyOptions isn't passed to hsdis library

[Schmidt, Lutz]

Hi Vladimir,

you are welcome. 

And you are right: the condition should read
    if ((options() != NULL) && (strlen(options()) == 0)) {
to be correct. I suggest we end this discussion and I just remove these checks.

All your other comments are valid. There is an open bug to address and improve the very basic options parsing: https://bugs.openjdk.java.net/browse/JDK-8223765 This task was split off from JDK-8213084.

I would like to cover the improvements you suggest when working on that bug. To make _print_raw work correctly, I suggest to just move 
    if (_optionsParsed) return;
a bit further down. The help text should be printed only once anyway.

Here is a new webrev iteration. It reflects what I suggest: https://cr.openjdk.java.net/~lucy/webrevs/8234583.01/ 

Thanks,
Lutz


On 25.11.19, 19:30, "Vladimir Ivanov" <vladimir.x.ivanov at oracle.com> wrote:

    Thanks for the clarifications, Lutz.
    
    So, I assume you have a typo in the patch then:
    
    +  if ((options() == NULL) || (strlen(options()) == 0)) {
    +    // We need to fill the options buffer for each newly created
    +    // decode_env instance. The hsdis_* library looks for options
    +    // in that buffer.
    +    collect_options(Disassembler::pd_cpu_opts());
    +    collect_options(PrintAssemblyOptions);
    +  }
    
    It performs collect_options() calls only if _option_buf is either NULL 
    or "\0".
    
    Also, what about the following updates of instance members?
    
       if (strstr(options(), "print-raw")) {
         _print_raw = (strstr(options(), "xml") ? 2 : 1);
       }
    
       if (strstr(options(), "help")) {
         _print_help = true;
       }
    
    BTW should _print_help (along with _helpPrinted) be better turned into 
    static member?
    
    Can we make _option_buf static as well? Or do we want to keep a 
    defensive copy to pass into hsdis.so?
    
    As an alternative approach to fix the bug, we could create a golden copy 
    during parsing instead and then just copy it to _option_buf as part of 
    decode_env initialization.
    
    Best regards,
    Vladimir Ivanov
    
    On 25.11.2019 19:59, Schmidt, Lutz wrote:
    > Hi Vladimir,
    > 
    > I'm happy to elaborate in more detail about the issue and the fix.
    > 
    > For each decode_env instance which is constructed, process_options() is called. It collects the disassembly options from various sources (Disassembler::pd_cpu_opts() and PrintAssemblyOptions), storing them in the private member "char _option_buf[512]".
    > 
    > Further processing derives static flag settings from these options. Being static, these flags need to be set only once, not every time a decode_env is constructed.
    > 
    > But that's just one part of the story. It was not taken into account that _option_buf is passed to and analyzed by hsdis-<platform>.so as well. That requires _option_buf to be filled every time a decode_env is constructed.
    > 
    > Moving
    >    if (_optionsParsed) return;
    > after the collect_options() calls heals this deficiency.
    > 
    > I added the guards you question as additional "safety net". After looking at the code again I must admit the guards are not necessary. _option_buf can never be NULL and every invocation of process_options() is directly preceded by a memset(_option_buf, 0, sizeof(_option_buf)). I can remove the guards if you like.
    > 
    > Please let me know if there are any more questions to be answered.
    > 
    > Thanks,
    > Lutz
    > 
    > 
    > On 25.11.19, 17:05, "Vladimir Ivanov" <vladimir.x.ivanov at oracle.com> wrote:
    > 
    >      Lutz,
    >      
    >      Can you elaborate, please, how the patch fixes the problem?
    >      
    >      Why did you decide to add the following guards?
    >      
    >      +  if ((options() == NULL) || (strlen(options()) == 0)) {
    >      
    >      Best regards,
    >      Vladimir Ivanov
    >      
    >      On 25.11.2019 17:06, Schmidt, Lutz wrote:
    >      > Dear all,
    >      >
    >      > may I please request reviews for this small change, fixing a regression in the disassembler. Parameters to the hsdis-<platform> library were not passed on.
    >      >
    >      > The change was verified to fix the issue by the reporter (Jean-Philippe Bempel, on CC:). jdk/submit tests pending...
    >      >
    >      > Bug:    https://bugs.openjdk.java.net/browse/JDK-8234583
    >      > Webrev: https://cr.openjdk.java.net/~lucy/webrevs/8234583.00/
    >      >
    >      > Thank you,
    >      > Lutz
    >      >
    >      
    >