Re: [Xen-devel] [PATCH 01/12] libxc/save: Shrink code volume where possible

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Andrew Cooper writes ("[PATCH 01/12] libxc/save: Shrink code volume where 
possible"):
> A property of how the error handling (0 on success, nonzero otherwise)
> allows these calls to be chained together with the ternary operatior.

I'm quite surprised to find a suggestion like this coming from you in
particular.  I think if we are going to adopt this thing in general,
it ought to be in a CODING_STYLE somewhere.

I'm distinctly unsure about the merits of the pattern.  It does make
the code much shorter and less repetitive.  OTOH ?: is a
not-very-frequently used GNU extension and my representative sample of
programmers had to think about what this idiom meant and it wasn't
universally liked.  On the third hand, if this idiom becomes dominant
you only have to think about it once.

Maybe it would be better to have
    #define MUST(call) ({ rc = (call); if (rc) goto error; })
and write
    MUST( write_one_vcpu_basic(ctx, i) );

Or just to permit
   rc = write_one_vcpu_basic(ctx, i);    if (rc) goto error;
(ie on a single line).

Ian.

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