[Spice-devel] [PATCH] log: add not fatal spice_return function

[David Jaša]

On Pá, 2015-11-20 at 16:26 +0100, Francois Gouget wrote:
> On Thu, 19 Nov 2015, Frediano Ziglio wrote:
> [...]
> > > What do you mean by "100% compatible with the current code"? (why is
> > > g_return_if-fail() not "100% compatible with the current code" ?)
> > 
> > well... implementation is quite different. I didn't get all differences but
> > - spice_logv use some environment SPICE_* specific (I doubt Glib does!);
> > - Glib output on standard error or output based on level;
> > - surely something I forgot!
> 
> Does it matter?
> The client uses the g_return_xxx() functions already. Would it be a 
> problem if the server did too instead of going its separate way?
> 

Without accompanying modification, yes. Users are taught that
spice-server logging is controlled by SPICE_DEBUG_LEVEL environment
variable. Glib debugging is controlled differently so if you just start
mixing spice_* and g_* logging functions, users will start silently
losing some debugging information...

So from users' perspective, switch to glib logging style should either
be atomic & properly announced, or gradual with something that would
turn on glib logging according to SPICE_DEBUG_LEVEL setting.

Note that client logging is not relevant here as spice-gtk follows glib
style since its inception, unlike spice-server.

David

> 
> > Didn't investigate so deep to be able to tell all list but surely just 
> > with these I'm not comfortable to do a sed and release tomorrow...
> 
> Let me summarize. Currently we have:
> 
> 1. Plain old and trustworthy assert().
>    Used by server/dispatcher.c.
> 
> 2. g_return_if_fail() which does not log the way spice functions do.
>    Used by server/reds_stream.c and most of the client code.
> 
> 3. spice_assert() which crashes the application.
>    Used by most of the server code but not by the client.
> 
> 4. spice_return_if_fail() which claims to return but instead crashes the 
>    application, exactly like spice_assert().
>    Also used in most of the server code but not by the client.
> 
> 5. And you propose adding spice_return_if_fail_warning() to fix this mess.
> 
> I really don't see how adding more functions is going to make this less 
> confusing and error prone! Particularly if there is not a concerted 
> and swift effort to clean up the old code.
> 
> Not fixing spice_return_if_fail() does not make any sense either (yes, a 
> functions that crashes the application under the guise of returning to 
> the caller is *totally* buggy).
> 
> The code calling spice_return_if_fail() was written under the assumption 
> that it would return. So just switch the default 
> SPICE_ABORT_LEVEL_DEFAULT to SPICE_LOG_LEVEL_ERROR.
> 
> But it would also really help if the different Spice pieces like the 
> server and client could agree on whether to use glib functions or not.
> 
> 
> Note that spice_error() needs to be fixed too. That name implies the 
> function logs an error just like spice_warning() logs a warning, not 
> that it crashes the application. spice_error() should be renamed to 
> spice_fatal(). For consistency it might make sense to rename 
> SPICE_LOG_LEVEL_ERROR to SPICE_LOG_LEVEL_FATAL.
> 
> 
> 
> Then there's memory handling where we see the same issues yet again:
> 
> 1. malloc() & co.
>    Used in server/red_replay_qxl.c and some lz encoders.
> 
> 2. spice_malloc() & co.
>    Used by most of the server code but not by the client.
> 
> 3. g_malloc() & co.
>    Use by most of spice-gtk and but only a test file on the server!
> 
> 
> This duplication of basic functionality needs to stop. It's confusing 
> and can only lead to bugs. Nobody wants to track for each pointer 
> whether it should be freed with free(), g_free() or the nonexistent 
> spice_free()!
> 
>  
> > Calling spice_* functions instead of spice_* functions looks like 100% compatible :)
> 
> I'm not very impressed by this argument. Do you mean that, just because 
> they both start with 'spice_', spice_assert() and spice_strndup() are 
> interchangeable?
> 
>