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>

1 files changed, 8 insertions, 16 deletions

diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index 2e6dabbbaf..aa831d6653 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -175,27 +175,23 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
     }
     if (object_property_find(OBJECT(s->cpu), "init-svtor", NULL)) {
         if (!object_property_set_uint(OBJECT(s->cpu), "init-svtor",
-                                      s->init_svtor, &err)) {
-            error_propagate(errp, err);
+                                      s->init_svtor, errp)) {
             return;
         }
     }
     if (object_property_find(OBJECT(s->cpu), "start-powered-off", NULL)) {
         if (!object_property_set_bool(OBJECT(s->cpu), "start-powered-off",
-                                      s->start_powered_off, &err)) {
-            error_propagate(errp, err);
+                                      s->start_powered_off, errp)) {
             return;
         }
     }
     if (object_property_find(OBJECT(s->cpu), "vfp", NULL)) {
-        if (!object_property_set_bool(OBJECT(s->cpu), "vfp", s->vfp, &err)) {
-            error_propagate(errp, err);
+        if (!object_property_set_bool(OBJECT(s->cpu), "vfp", s->vfp, errp)) {
             return;
         }
     }
     if (object_property_find(OBJECT(s->cpu), "dsp", NULL)) {
-        if (!object_property_set_bool(OBJECT(s->cpu), "dsp", s->dsp, &err)) {
-            error_propagate(errp, err);
+        if (!object_property_set_bool(OBJECT(s->cpu), "dsp", s->dsp, errp)) {
             return;
         }
     }
@@ -207,14 +203,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
     s->cpu->env.nvic = &s->nvic;
     s->nvic.cpu = s->cpu;
 
-    if (!qdev_realize(DEVICE(s->cpu), NULL, &err)) {
-        error_propagate(errp, err);
+    if (!qdev_realize(DEVICE(s->cpu), NULL, errp)) {
         return;
     }
 
     /* Note that we must realize the NVIC after the CPU */
-    if (!sysbus_realize(SYS_BUS_DEVICE(&s->nvic), &err)) {
-        error_propagate(errp, err);
+    if (!sysbus_realize(SYS_BUS_DEVICE(&s->nvic), errp)) {
         return;
     }
 
@@ -240,14 +234,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
             SysBusDevice *sbd = SYS_BUS_DEVICE(&s->bitband[i]);
 
             if (!object_property_set_int(obj, "base",
-                                         bitband_input_addr[i], &err)) {
-                error_propagate(errp, err);
+                                         bitband_input_addr[i], errp)) {
                 return;
             }
             object_property_set_link(obj, "source-memory",
                                      OBJECT(s->board_memory), &error_abort);
-            if (!sysbus_realize(SYS_BUS_DEVICE(obj), &err)) {
-                error_propagate(errp, err);
+            if (!sysbus_realize(SYS_BUS_DEVICE(obj), errp)) {
                 return;
             }