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, 3 insertions, 8 deletions

diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
index f3ba30e93e..c2af226174 100644
--- a/target/s390x/cpu_models.c
+++ b/target/s390x/cpu_models.c
@@ -510,8 +510,7 @@ static void cpu_model_from_info(S390CPUModel *model, const CpuModelInfo *info,
 
     if (qdict) {
         visitor = qobject_input_visitor_new(info->props);
-        if (!visit_start_struct(visitor, NULL, NULL, 0, &err)) {
-            error_propagate(errp, err);
+        if (!visit_start_struct(visitor, NULL, NULL, 0, errp)) {
             visit_free(visitor);
             object_unref(obj);
             return;
@@ -999,7 +998,6 @@ static void get_feature(Object *obj, Visitor *v, const char *name,
 static void set_feature(Object *obj, Visitor *v, const char *name,
                         void *opaque, Error **errp)
 {
-    Error *err = NULL;
     S390Feat feat = (S390Feat) opaque;
     DeviceState *dev = DEVICE(obj);
     S390CPU *cpu = S390_CPU(obj);
@@ -1015,8 +1013,7 @@ static void set_feature(Object *obj, Visitor *v, const char *name,
         return;
     }
 
-    if (!visit_type_bool(v, name, &value, &err)) {
-        error_propagate(errp, err);
+    if (!visit_type_bool(v, name, &value, errp)) {
         return;
     }
     if (value) {
@@ -1056,7 +1053,6 @@ static void get_feature_group(Object *obj, Visitor *v, const char *name,
 static void set_feature_group(Object *obj, Visitor *v, const char *name,
                               void *opaque, Error **errp)
 {
-    Error *err = NULL;
     S390FeatGroup group = (S390FeatGroup) opaque;
     const S390FeatGroupDef *def = s390_feat_group_def(group);
     DeviceState *dev = DEVICE(obj);
@@ -1073,8 +1069,7 @@ static void set_feature_group(Object *obj, Visitor *v, const char *name,
         return;
     }
 
-    if (!visit_type_bool(v, name, &value, &err)) {
-        error_propagate(errp, err);
+    if (!visit_type_bool(v, name, &value, errp)) {
         return;
     }
     if (value) {