qemu/backends
Markus Armbruster 668f62ec62 error: Eliminate error_propagate() with Coccinelle, part 1
When all we do with an Error we receive into a local variable is
propagating to somewhere else, we can just as well receive it there
right away.  Convert

    if (!foo(..., &err)) {
        ...
        error_propagate(errp, err);
        ...
        return ...
    }

to

    if (!foo(..., errp)) {
        ...
        ...
        return ...
    }

where nothing else needs @err.  Coccinelle script:

    @rule1 forall@
    identifier fun, err, errp, lbl;
    expression list args, args2;
    binary operator op;
    constant c1, c2;
    symbol false;
    @@
         if (
    (
    -        fun(args, &err, args2)
    +        fun(args, errp, args2)
    |
    -        !fun(args, &err, args2)
    +        !fun(args, errp, args2)
    |
    -        fun(args, &err, args2) op c1
    +        fun(args, errp, args2) op c1
    )
            )
         {
             ... when != err
                 when != lbl:
                 when strict
    -        error_propagate(errp, err);
             ... when != err
    (
             return;
    |
             return c2;
    |
             return false;
    )
         }

    @rule2 forall@
    identifier fun, err, errp, lbl;
    expression list args, args2;
    expression var;
    binary operator op;
    constant c1, c2;
    symbol false;
    @@
    -    var = fun(args, &err, args2);
    +    var = fun(args, errp, args2);
         ... when != err
         if (
    (
             var
    |
             !var
    |
             var op c1
    )
            )
         {
             ... when != err
                 when != lbl:
                 when strict
    -        error_propagate(errp, err);
             ... when != err
    (
             return;
    |
             return c2;
    |
             return false;
    |
             return var;
    )
         }

    @depends on rule1 || rule2@
    identifier err;
    @@
    -    Error *err = NULL;
         ... when != err

Not exactly elegant, I'm afraid.

The "when != lbl:" is necessary to avoid transforming

         if (fun(args, &err)) {
             goto out
         }
         ...
     out:
         error_propagate(errp, err);

even though other paths to label out still need the error_propagate().
For an actual example, see sclp_realize().

Without the "when strict", Coccinelle transforms vfio_msix_setup(),
incorrectly.  I don't know what exactly "when strict" does, only that
it helps here.

The match of return is narrower than what I want, but I can't figure
out how to express "return where the operand doesn't use @err".  For
an example where it's too narrow, see vfio_intx_enable().

Silently fails to convert hw/arm/armsse.c, because Coccinelle gets
confused by ARMSSE being used both as typedef and function-like macro
there.  Converted manually.

Line breaks tidied up manually.  One nested declaration of @local_err
deleted manually.  Preexisting unwanted blank line dropped in
hw/riscv/sifive_e.c.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200707160613.848843-35-armbru@redhat.com>
2020-07-10 15:18:08 +02:00
..
tpm error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
cryptodev-builtin.c cryptodev: Fix cryptodev_builtin_cleanup() error API violation 2020-04-29 08:01:52 +02:00
cryptodev-vhost-user.c error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
cryptodev-vhost.c cryptodev: add vhost support 2018-03-01 18:26:17 +02:00
cryptodev.c error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
dbus-vmstate.c qom: Drop parameter @errp of object_property_add() & friends 2020-05-15 07:07:58 +02:00
hostmem-file.c error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
hostmem-memfd.c error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
hostmem-ram.c machine: alias -mem-path and -mem-prealloc into memory-foo backend 2020-02-19 16:49:53 +00:00
hostmem.c error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
Kconfig tpm: Move backend code under the 'backends/' directory 2020-06-19 07:25:55 -04:00
Makefile.objs backends: Add TPM files into their own directory 2020-06-19 07:24:42 -04:00
rng-builtin.c virtio-rng: change default backend to rng-builtin 2019-09-04 06:32:51 -04:00
rng-egd.c qom: Drop parameter @errp of object_property_add() & friends 2020-05-15 07:07:58 +02:00
rng-random.c qom: Drop parameter @errp of object_property_add() & friends 2020-05-15 07:07:58 +02:00
rng.c qom: Put name parameter before value / visitor parameter 2020-07-10 15:18:08 +02:00
trace-events Add dbus-vmstate object 2020-01-06 18:41:32 +04:00
vhost-user.c qom: Drop parameter @errp of object_property_add() & friends 2020-05-15 07:07:58 +02:00