Re: [PATCH] Print die_hash2 for --odr --devel-dump-dies

[Tom de Vries <tdevries@suse.de>]

On 2/18/21 4:03 PM, Mark Wielaard wrote:
> Hi Tom,
> 
> On Mon, 2021-02-15 at 21:34 +0100, Tom de Vries wrote:
>> For --odr, there's an additional hash value, die->u.p1.die_hash2.
>>
>> Print this with --devel-dump-dies, such that we have:
>> ...
>> $ dwz --devel-dump-dies --odr odr-struct
>>   114 O f56004ac(cd46c7ab) f56004ac aaa structure_type
>>   ...
>>   1ba O f56004ac(cd46c7ab) f56004ac aaa structure_type
>> ...
>>
>> Used to debug PR27400.
>>
>> Any comments?
> 
> Obviously this is useful.
> But I always forget how to use these --devel flags.
> 
> They are only in the dwz-for-test binary, which isn't build by default,

Hi Mark,

they're only defined when building with -DDEVEL.  Which is enabled in
dwz-for-test (which is enabled by default in the testsuite), but also in
my usual build command.

> and seems to have some subtle other differences, like undefining
> __GNUC__?
> 

That's just a ploy to get both the -D__GNUC__ and -U__GNUC__ paths
exercised.  It's not really specific to -DDEVEL.

> Is there more documentation on the --devel flags/binary

Nope.

> or is this just
> meant for people directly hacking on dwz in the git repo?

Yep.

The idea was to move all hacky stuff (like f.i -DDEBUG_DUMP_DIES) to
command line switches under -DDEVEL, such that you have two versions:
- the official one, -UDEVEL, without anything slowing dwz down, or
  exposing unstable interfaces to users, and
- the development one, -DDEVEL, with the perks of extra traces
  and switches to influence behaviour, but possible slower and
  experimental.

HTH,
- Tom