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>

3 files changed, 5 insertions, 13 deletions

diff --git a/hw/pci-host/pnv_phb3.c b/hw/pci-host/pnv_phb3.c
index 94cb989136..82132c12ca 100644
--- a/hw/pci-host/pnv_phb3.c
+++ b/hw/pci-host/pnv_phb3.c
@@ -990,7 +990,6 @@ static void pnv_phb3_realize(DeviceState *dev, Error **errp)
     PnvPHB3 *phb = PNV_PHB3(dev);
     PCIHostState *pci = PCI_HOST_BRIDGE(dev);
     PnvMachineState *pnv = PNV_MACHINE(qdev_get_machine());
-    Error *local_err = NULL;
     int i;
 
     if (phb->phb_id >= PNV8_CHIP_PHB3_MAX) {
@@ -1003,8 +1002,7 @@ static void pnv_phb3_realize(DeviceState *dev, Error **errp)
                              &error_abort);
     object_property_set_int(OBJECT(&phb->lsis), "nr-irqs", PNV_PHB3_NUM_LSI,
                             &error_abort);
-    if (!qdev_realize(DEVICE(&phb->lsis), NULL, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!qdev_realize(DEVICE(&phb->lsis), NULL, errp)) {
         return;
     }
 
@@ -1021,16 +1019,14 @@ static void pnv_phb3_realize(DeviceState *dev, Error **errp)
                              &error_abort);
     object_property_set_int(OBJECT(&phb->msis), "nr-irqs", PHB3_MAX_MSI,
                             &error_abort);
-    if (!qdev_realize(DEVICE(&phb->msis), NULL, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!qdev_realize(DEVICE(&phb->msis), NULL, errp)) {
         return;
     }
 
     /* Power Bus Common Queue */
     object_property_set_link(OBJECT(&phb->pbcq), "phb", OBJECT(phb),
                              &error_abort);
-    if (!qdev_realize(DEVICE(&phb->pbcq), NULL, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!qdev_realize(DEVICE(&phb->pbcq), NULL, errp)) {
         return;
     }
 
diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
index a598c89eb0..75ad766fe0 100644
--- a/hw/pci-host/pnv_phb4.c
+++ b/hw/pci-host/pnv_phb4.c
@@ -1169,7 +1169,6 @@ static void pnv_phb4_realize(DeviceState *dev, Error **errp)
     PnvPHB4 *phb = PNV_PHB4(dev);
     PCIHostState *pci = PCI_HOST_BRIDGE(dev);
     XiveSource *xsrc = &phb->xsrc;
-    Error *local_err = NULL;
     int nr_irqs;
     char name[32];
 
@@ -1218,8 +1217,7 @@ static void pnv_phb4_realize(DeviceState *dev, Error **errp)
     }
     object_property_set_int(OBJECT(xsrc), "nr-irqs", nr_irqs, &error_fatal);
     object_property_set_link(OBJECT(xsrc), "xive", OBJECT(phb), &error_fatal);
-    if (!qdev_realize(DEVICE(xsrc), NULL, &local_err)) {
-        error_propagate(errp, local_err);
+    if (!qdev_realize(DEVICE(xsrc), NULL, errp)) {
         return;
     }
 
diff --git a/hw/pci-host/pnv_phb4_pec.c b/hw/pci-host/pnv_phb4_pec.c
index 088ab753aa..741ddc90ed 100644
--- a/hw/pci-host/pnv_phb4_pec.c
+++ b/hw/pci-host/pnv_phb4_pec.c
@@ -377,7 +377,6 @@ static void pnv_pec_instance_init(Object *obj)
 static void pnv_pec_realize(DeviceState *dev, Error **errp)
 {
     PnvPhb4PecState *pec = PNV_PHB4_PEC(dev);
-    Error *local_err = NULL;
     char name[64];
     int i;
 
@@ -390,8 +389,7 @@ static void pnv_pec_realize(DeviceState *dev, Error **errp)
 
         object_property_set_int(stk_obj, "stack-no", i, &error_abort);
         object_property_set_link(stk_obj, "pec", OBJECT(pec), &error_abort);
-        if (!qdev_realize(DEVICE(stk_obj), NULL, &local_err)) {
-            error_propagate(errp, local_err);
+        if (!qdev_realize(DEVICE(stk_obj), NULL, errp)) {
             return;
         }
     }