[Qemu-devel] [Bug 1321464] [NEW] qemu/block/qcow2.c:1942: possible performance problem ?

[dcb]

Public bug reported:

I just ran static analyser cppcheck over today (20140520) qemu source
code.

It said many things, including

[qemu/block/qcow2.c:1942] -> [qemu/block/qcow2.c:1943]: (performance) Buffer 
'pad_buf' is being writ
ten before its old content has been used.

Source code is

            memset(pad_buf, 0, s->cluster_size);
            memcpy(pad_buf, buf, nb_sectors * BDRV_SECTOR_SIZE);

Worth tuning ?

Similar problem here

[qemu/block/qcow.c:815] -> [qemu/block/qcow.c:816]: (performance) Buffer 
'pad_buf' is being written 
before its old content has been used.

and

[qemu/hw/i386/acpi-build.c:1265] -> [qemu/hw/i386/acpi-build.c:1267]: 
(performance) Buffer 'dsdt' is
 being written before its old content has been used.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1321464

Title:
  qemu/block/qcow2.c:1942: possible performance problem ?

Status in QEMU:
  New

Bug description:
  I just ran static analyser cppcheck over today (20140520) qemu source
  code.

  It said many things, including

  [qemu/block/qcow2.c:1942] -> [qemu/block/qcow2.c:1943]: (performance) Buffer 
'pad_buf' is being writ
  ten before its old content has been used.

  Source code is

              memset(pad_buf, 0, s->cluster_size);
              memcpy(pad_buf, buf, nb_sectors * BDRV_SECTOR_SIZE);

  Worth tuning ?

  Similar problem here

  [qemu/block/qcow.c:815] -> [qemu/block/qcow.c:816]: (performance) Buffer 
'pad_buf' is being written 
  before its old content has been used.

  and

  [qemu/hw/i386/acpi-build.c:1265] -> [qemu/hw/i386/acpi-build.c:1267]: 
(performance) Buffer 'dsdt' is
   being written before its old content has been used.

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