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, 7 insertions, 15 deletions

diff --git a/hw/arm/stm32f205_soc.c b/hw/arm/stm32f205_soc.c
index 9acf401fbf..a4f3344db2 100644
--- a/hw/arm/stm32f205_soc.c
+++ b/hw/arm/stm32f205_soc.c
@@ -81,7 +81,6 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
     STM32F205State *s = STM32F205_SOC(dev_soc);
     DeviceState *dev, *armv7m;
     SysBusDevice *busdev;
-    Error *err = NULL;
     int i;
 
     MemoryRegion *system_memory = get_system_memory();
@@ -107,15 +106,13 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
     qdev_prop_set_bit(armv7m, "enable-bitband", true);
     object_property_set_link(OBJECT(&s->armv7m), "memory",
                              OBJECT(get_system_memory()), &error_abort);
-    if (!sysbus_realize(SYS_BUS_DEVICE(&s->armv7m), &err)) {
-        error_propagate(errp, err);
+    if (!sysbus_realize(SYS_BUS_DEVICE(&s->armv7m), errp)) {
         return;
     }
 
     /* System configuration controller */
     dev = DEVICE(&s->syscfg);
-    if (!sysbus_realize(SYS_BUS_DEVICE(&s->syscfg), &err)) {
-        error_propagate(errp, err);
+    if (!sysbus_realize(SYS_BUS_DEVICE(&s->syscfg), errp)) {
         return;
     }
     busdev = SYS_BUS_DEVICE(dev);
@@ -126,8 +123,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
     for (i = 0; i < STM_NUM_USARTS; i++) {
         dev = DEVICE(&(s->usart[i]));
         qdev_prop_set_chr(dev, "chardev", serial_hd(i));
-        if (!sysbus_realize(SYS_BUS_DEVICE(&s->usart[i]), &err)) {
-            error_propagate(errp, err);
+        if (!sysbus_realize(SYS_BUS_DEVICE(&s->usart[i]), errp)) {
             return;
         }
         busdev = SYS_BUS_DEVICE(dev);
@@ -139,8 +135,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
     for (i = 0; i < STM_NUM_TIMERS; i++) {
         dev = DEVICE(&(s->timer[i]));
         qdev_prop_set_uint64(dev, "clock-frequency", 1000000000);
-        if (!sysbus_realize(SYS_BUS_DEVICE(&s->timer[i]), &err)) {
-            error_propagate(errp, err);
+        if (!sysbus_realize(SYS_BUS_DEVICE(&s->timer[i]), errp)) {
             return;
         }
         busdev = SYS_BUS_DEVICE(dev);
@@ -151,8 +146,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
     /* ADC 1 to 3 */
     object_property_set_int(OBJECT(s->adc_irqs), "num-lines", STM_NUM_ADCS,
                             &error_abort);
-    if (!qdev_realize(DEVICE(s->adc_irqs), NULL, &err)) {
-        error_propagate(errp, err);
+    if (!qdev_realize(DEVICE(s->adc_irqs), NULL, errp)) {
         return;
     }
     qdev_connect_gpio_out(DEVICE(s->adc_irqs), 0,
@@ -160,8 +154,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
 
     for (i = 0; i < STM_NUM_ADCS; i++) {
         dev = DEVICE(&(s->adc[i]));
-        if (!sysbus_realize(SYS_BUS_DEVICE(&s->adc[i]), &err)) {
-            error_propagate(errp, err);
+        if (!sysbus_realize(SYS_BUS_DEVICE(&s->adc[i]), errp)) {
             return;
         }
         busdev = SYS_BUS_DEVICE(dev);
@@ -173,8 +166,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
     /* SPI 1 and 2 */
     for (i = 0; i < STM_NUM_SPIS; i++) {
         dev = DEVICE(&(s->spi[i]));
-        if (!sysbus_realize(SYS_BUS_DEVICE(&s->spi[i]), &err)) {
-            error_propagate(errp, err);
+        if (!sysbus_realize(SYS_BUS_DEVICE(&s->spi[i]), errp)) {
             return;
         }
         busdev = SYS_BUS_DEVICE(dev);