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, 24 deletions

diff --git a/qom/object.c b/qom/object.c
index 07618816a7..08b2cad445 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -800,15 +800,13 @@ bool object_set_propv(Object *obj,
                      va_list vargs)
 {
     const char *propname;
-    Error *local_err = NULL;
 
     propname = va_arg(vargs, char *);
     while (propname != NULL) {
         const char *value = va_arg(vargs, char *);
 
         g_assert(value != NULL);
-        if (!object_property_parse(obj, propname, value, &local_err)) {
-            error_propagate(errp, local_err);
+        if (!object_property_parse(obj, propname, value, errp)) {
             return false;
         }
         propname = va_arg(vargs, char *);
@@ -2115,10 +2113,8 @@ static void property_set_str(Object *obj, Visitor *v, const char *name,
 {
     StringProperty *prop = opaque;
     char *value;
-    Error *local_err = NULL;
 
-    if (!visit_type_str(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_str(v, name, &value, errp)) {
         return;
     }
 
@@ -2195,10 +2191,8 @@ static void property_set_bool(Object *obj, Visitor *v, const char *name,
 {
     BoolProperty *prop = opaque;
     bool value;
-    Error *local_err = NULL;
 
-    if (!visit_type_bool(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_bool(v, name, &value, errp)) {
         return;
     }
 
@@ -2267,10 +2261,8 @@ static void property_set_enum(Object *obj, Visitor *v, const char *name,
 {
     EnumProperty *prop = opaque;
     int value;
-    Error *err = NULL;
 
-    if (!visit_type_enum(v, name, &value, prop->lookup, &err)) {
-        error_propagate(errp, err);
+    if (!visit_type_enum(v, name, &value, prop->lookup, errp)) {
         return;
     }
     prop->set(obj, value, errp);
@@ -2419,10 +2411,8 @@ static void property_set_uint8_ptr(Object *obj, Visitor *v, const char *name,
 {
     uint8_t *field = opaque;
     uint8_t value;
-    Error *local_err = NULL;
 
-    if (!visit_type_uint8(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_uint8(v, name, &value, errp)) {
         return;
     }
 
@@ -2441,10 +2431,8 @@ static void property_set_uint16_ptr(Object *obj, Visitor *v, const char *name,
 {
     uint16_t *field = opaque;
     uint16_t value;
-    Error *local_err = NULL;
 
-    if (!visit_type_uint16(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_uint16(v, name, &value, errp)) {
         return;
     }
 
@@ -2463,10 +2451,8 @@ static void property_set_uint32_ptr(Object *obj, Visitor *v, const char *name,
 {
     uint32_t *field = opaque;
     uint32_t value;
-    Error *local_err = NULL;
 
-    if (!visit_type_uint32(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_uint32(v, name, &value, errp)) {
         return;
     }
 
@@ -2485,10 +2471,8 @@ static void property_set_uint64_ptr(Object *obj, Visitor *v, const char *name,
 {
     uint64_t *field = opaque;
     uint64_t value;
-    Error *local_err = NULL;
 
-    if (!visit_type_uint64(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_uint64(v, name, &value, errp)) {
         return;
     }