RFR (S): 8004747: Remove last_entry from VM_STRUCT macros

[David Holmes]

Hi Mikael,

This looks okay to me - I like the simplification. However as I don't 
perform mental macro substitution particularly well (okay, not at all 
;-)) I was wondering if there was a simple validation test where we 
could compare the pre-processed output before and after?

Thanks,
David

On 11/12/2012 7:01 AM, Mikael Vidstedt wrote:
>
> Please review the following change:
>
> Webrev: http://cr.openjdk.java.net/~mikael/8004747/webrev.00/
>
> Background:
>
> This patch does 3 things (depending on how you count it):
>
> 1. Move the call to generating the last entry for the VM structures
> database
>
> The vmStructs functionality is a macro based way of creating a database
> of information about VM internal structures, types and constants.
>
> The database for structures is defined in runtime/vmStructs.cpp in an
> array called localHotSpotVMStructs. The content of the array is
> generated with calls to a few different macros (VM_STRUCTS,
> VM_STRUCTS_PARALLELGC, VM_STRUCTS_CMS, VM_STRUCTS_G1, VM_STRUCTS_CPU and
> VM_STRUCTS_OS_CPU respectively). Common for all these macros is the fact
> that the last argument passed in is another macro
> (GENERATE_VM_STRUCT_LAST_ENTRY) which is a generator for the end
> marker/last entry in the database; a special entry which can be easily
> located by an external consumer of the information.
>
> Even though the end marker generator macro
> (GENERATE_VM_STRUCT_LAST_ENTRY) is passed to all the VM_STRUCT* macros,
> the actual end marker must be generated once and only once. The way this
> is currently handled is that only the last VM_STRUCT macro, which
> happens to be VM_STRUCTS_OS_CPU, actually makes use of its last argument
> and adds it to the end of the array.
>
> Not only is this fairly complex to understand, it's also more fragile
> than it needs to be.
>
> This change removes the last argument for all the VM_STRUCT macros and
> instead explicitly inserts the end marker at the end of the
> localHotSpotVMStructs array.
>
> The same VM_STRUCTS macros are being used in VMStructs::init to do type
> checking. Instead of passing the end marker generator into the macros
> the last parameter is instead CHECK_SENTINEL, which is defined to expand
> to nothing, which means it can be safely removed.
>
> 2. Move the end marker generating for the VM types, VM int constants and
> VM long constants databases
>
> Repeat the exact above story, but replace anything called Structs/STRUCT
> with Types/TYPES, IntConstants/INT_CONSTANTS and
> LongConstants/LONG_CONSTANTS respectively.
>
> 3. Minor prettification
>
> In addition to the above the change also removes some superfluous
> backslashes from a few of the VM_STRUCT* macro calls.
>
> Thanks,
> Mikael
>