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[PATCH for 6.0 v2] hw/intc/i8259: Refactor pic_read_irq() to avoid unini


From: Philippe Mathieu-Daudé
Subject: [PATCH for 6.0 v2] hw/intc/i8259: Refactor pic_read_irq() to avoid uninitialized variable
Date: Thu, 18 Mar 2021 17:09:49 +0100

Some compiler versions are smart enough to detect a potentially
uninitialized variable, but are not smart enough to detect that this
cannot happen due to the code flow:

../hw/intc/i8259.c: In function ‘pic_read_irq’:
../hw/intc/i8259.c:203:13: error: ‘irq2’ may be used uninitialized in this 
function [-Werror=maybe-uninitialized]
   203 |         irq = irq2 + 8;
       |         ~~~~^~~~~~~~~~

Restrict irq2 variable use to the inner statement.

Fixes: 78ef2b6989f ("i8259: Reorder intack in pic_read_irq")
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
Supersedes: <20210318154738.27094-1-borntraeger@de.ibm.com>
---
 hw/intc/i8259.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/hw/intc/i8259.c b/hw/intc/i8259.c
index 344fd04db14..52c039c6c03 100644
--- a/hw/intc/i8259.c
+++ b/hw/intc/i8259.c
@@ -176,10 +176,12 @@ static void pic_intack(PICCommonState *s, int irq)
 int pic_read_irq(DeviceState *d)
 {
     PICCommonState *s = PIC_COMMON(d);
-    int irq, irq2, intno;
+    int irq, intno;
 
     irq = pic_get_irq(s);
     if (irq >= 0) {
+        int irq2;
+
         if (irq == 2) {
             irq2 = pic_get_irq(slave_pic);
             if (irq2 >= 0) {
@@ -189,8 +191,11 @@ int pic_read_irq(DeviceState *d)
                 irq2 = 7;
             }
             intno = slave_pic->irq_base + irq2;
+            pic_intack(s, irq);
+            irq = irq2 + 8;
         } else {
             intno = s->irq_base + irq;
+            pic_intack(s, irq);
         }
         pic_intack(s, irq);
     } else {
@@ -199,10 +204,6 @@ int pic_read_irq(DeviceState *d)
         intno = s->irq_base + irq;
     }
 
-    if (irq == 2) {
-        irq = irq2 + 8;
-    }
-
 #ifdef DEBUG_IRQ_LATENCY
     printf("IRQ%d latency=%0.3fus\n",
            irq,
-- 
2.26.2




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