qemu/target
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
..
alpha accel/tcg: Relax va restrictions on 64-bit guests 2020-05-15 15:25:16 +01:00
arm error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
cris x86 and machine queue for 5.0 soft freeze 2020-03-19 14:22:46 +00:00
hppa softfloat: Name compare relation enum 2020-05-19 08:41:45 -07:00
i386 error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
lm32 x86 and machine queue for 5.0 soft freeze 2020-03-19 14:22:46 +00:00
m68k target/m68k: consolidate physical translation offset into get_physical_address() 2020-07-06 21:39:57 +02:00
microblaze target/microblaze: monitor: Increase the number of registers reported 2020-05-14 16:01:02 +02:00
mips hw/mips: Implement the kvm_type() hook in MachineClass 2020-06-27 19:35:39 +02:00
moxie cpu: Use DeviceClass reset instead of a special CPUClass reset 2020-03-17 19:48:10 -04:00
nios2 x86 and machine queue for 5.0 soft freeze 2020-03-19 14:22:46 +00:00
openrisc softfloat: Name compare relation enum 2020-05-19 08:41:45 -07:00
ppc error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
riscv target/riscv: configure and turn on vector extension from command line 2020-07-02 09:19:34 -07:00
rx target/rx/translate: Add missing fall through comment 2020-04-07 18:45:54 -07:00
s390x error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
sh4 gdbstub: Introduce gdb_get_float32() to get 32-bit float registers 2020-04-15 11:38:23 +01:00
sparc error: Eliminate error_propagate() with Coccinelle, part 1 2020-07-10 15:18:08 +02:00
tilegx cpu: Use DeviceClass reset instead of a special CPUClass reset 2020-03-17 19:48:10 -04:00
tricore target/tricore: Implement gdbstub 2020-06-01 16:55:13 +02:00
unicore32 target/unicore32: Prefer qemu_semihosting_log_out() over curses 2020-06-09 19:58:53 +02:00
xtensa target/xtensa fixes for 5.1: 2020-06-25 21:20:45 +01:00