[Qemu-devel] [PATCH] hw/ide/ahci.c: Fix shift left into sign bit

[Peter Maydell <peter.maydell@linaro.org>]

Avoid undefined behaviour from shifting left into the sign bit:

hw/ide/ahci.c:551:36: runtime error: left shift of 255 by 24 places cannot be represented in type 'int'

(Unfortunately C's promotion rules mean that in the expression
"some_uint8_t_variable << 24" the LHS gets promoted to signed
int before shifting.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
clang's undefined sanitizer produces a lot of copies of this warning during
'make check'...

 hw/ide/ahci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index 796be15..21f76ed 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -548,7 +548,7 @@ static void ahci_init_d2h(AHCIDevice *ad)
         ad->init_d2h_sent = true;
         /* We're emulating receiving the first Reg H2D Fis from the device;
          * Update the SIG register, but otherwise proceed as normal. */
-        pr->sig = (ide_state->hcyl << 24) |
+        pr->sig = ((uint32_t)ide_state->hcyl << 24) |
             (ide_state->lcyl << 16) |
             (ide_state->sector << 8) |
             (ide_state->nsector & 0xFF);
-- 
1.9.1