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>

6 files changed, 7 insertions, 20 deletions

diff --git a/backends/cryptodev-vhost-user.c b/backends/cryptodev-vhost-user.c
index 8b8cbc4223..dbe5a8aae6 100644
--- a/backends/cryptodev-vhost-user.c
+++ b/backends/cryptodev-vhost-user.c
@@ -209,8 +209,7 @@ static void cryptodev_vhost_user_init(
         backend->conf.peers.ccs[i] = cc;
 
         if (i == 0) {
-            if (!qemu_chr_fe_init(&s->chr, chr, &local_err)) {
-                error_propagate(errp, local_err);
+            if (!qemu_chr_fe_init(&s->chr, chr, errp)) {
                 return;
             }
         }
diff --git a/backends/cryptodev.c b/backends/cryptodev.c
index 4de378532b..ada4ebe78b 100644
--- a/backends/cryptodev.c
+++ b/backends/cryptodev.c
@@ -154,11 +154,9 @@ cryptodev_backend_set_queues(Object *obj, Visitor *v, const char *name,
                              void *opaque, Error **errp)
 {
     CryptoDevBackend *backend = CRYPTODEV_BACKEND(obj);
-    Error *local_err = NULL;
     uint32_t value;
 
-    if (!visit_type_uint32(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_uint32(v, name, &value, errp)) {
         return;
     }
     if (!value) {
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index a44f5a61ac..5b819020b4 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -110,7 +110,6 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(o);
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
-    Error *local_err = NULL;
     uint64_t val;
 
     if (host_memory_backend_mr_inited(backend)) {
@@ -119,8 +118,7 @@ static void file_memory_backend_set_align(Object *o, Visitor *v,
         return;
     }
 
-    if (!visit_type_size(v, name, &val, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_size(v, name, &val, errp)) {
         return;
     }
     fb->align = val;
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 1e74a2b92f..4c040a7541 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -77,7 +77,6 @@ memfd_backend_set_hugetlbsize(Object *obj, Visitor *v, const char *name,
                               void *opaque, Error **errp)
 {
     HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
-    Error *local_err = NULL;
     uint64_t value;
 
     if (host_memory_backend_mr_inited(MEMORY_BACKEND(obj))) {
@@ -85,8 +84,7 @@ memfd_backend_set_hugetlbsize(Object *obj, Visitor *v, const char *name,
         return;
     }
 
-    if (!visit_type_size(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_size(v, name, &value, errp)) {
         return;
     }
     if (!value) {
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 5cc264b0db..c614f1bdc1 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -54,7 +54,6 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
                              void *opaque, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
-    Error *local_err = NULL;
     uint64_t value;
 
     if (host_memory_backend_mr_inited(backend)) {
@@ -63,8 +62,7 @@ host_memory_backend_set_size(Object *obj, Visitor *v, const char *name,
         return;
     }
 
-    if (!visit_type_size(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_size(v, name, &value, errp)) {
         return;
     }
     if (!value) {
@@ -252,11 +250,9 @@ static void host_memory_backend_set_prealloc_threads(Object *obj, Visitor *v,
     const char *name, void *opaque, Error **errp)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
-    Error *local_err = NULL;
     uint32_t value;
 
-    if (!visit_type_uint32(v, name, &value, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_uint32(v, name, &value, errp)) {
         return;
     }
     if (value <= 0) {
diff --git a/backends/tpm/tpm_util.c b/backends/tpm/tpm_util.c
index 971f3af047..b58d298c1a 100644
--- a/backends/tpm/tpm_util.c
+++ b/backends/tpm/tpm_util.c
@@ -48,7 +48,6 @@ static void set_tpm(Object *obj, Visitor *v, const char *name, void *opaque,
                     Error **errp)
 {
     DeviceState *dev = DEVICE(obj);
-    Error *local_err = NULL;
     Property *prop = opaque;
     TPMBackend *s, **be = qdev_get_prop_ptr(dev, prop);
     char *str;
@@ -58,8 +57,7 @@ static void set_tpm(Object *obj, Visitor *v, const char *name, void *opaque,
         return;
     }
 
-    if (!visit_type_str(v, name, &str, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!visit_type_str(v, name, &str, errp)) {
         return;
     }