[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH] qcow2: Use a GString in report_unsupported_feature()
From: |
Alex Bennée |
Subject: |
Re: [PATCH] qcow2: Use a GString in report_unsupported_feature() |
Date: |
Tue, 14 Jan 2020 21:35:15 +0000 |
User-agent: |
mu4e 1.3.6; emacs 28.0.50 |
Philippe Mathieu-Daudé <address@hidden> writes:
> On 1/14/20 7:08 PM, Alex Bennée wrote:
>> Alberto Garcia <address@hidden> writes:
>>
>>> This is a bit more efficient than having to allocate and free memory
>>> for each item.
>>>
>>> The default size (60) is enough for all the existing incompatible
>>> features.
>>>
>>> Suggested-by: Philippe Mathieu-Daudé <address@hidden>
>>> Signed-off-by: Alberto Garcia <address@hidden>
>>> ---
>>> block/qcow2.c | 24 ++++++++++++------------
>>> 1 file changed, 12 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/block/qcow2.c b/block/qcow2.c
>>> index cef9d72b3a..ecf6827420 100644
>>> --- a/block/qcow2.c
>>> +++ b/block/qcow2.c
>>> @@ -453,16 +453,15 @@ static void
>>> cleanup_unknown_header_ext(BlockDriverState *bs)
>>> static void report_unsupported_feature(Error **errp, Qcow2Feature *table,
>>> uint64_t mask)
>>> {
>>> - char *features = g_strdup("");
>>> - char *old;
>>> + GString *features = g_string_sized_new(60);
>> g_autoptr(GString) features = g_string_sized_new(60);
>> will save you the clean-up later.
>
> Does this work with g_string_free() too?
It does:
static inline void g_autoptr_cleanup_gstring_free (GString *string)
{
if (string)
g_string_free (string, TRUE);
}
If you want to keep the allocated string but drop the GString you are
still best doing that yourself.
>
>>> while (table && table->name[0] != '\0') {
>>> if (table->type == QCOW2_FEAT_TYPE_INCOMPATIBLE) {
>>> if (mask & (1ULL << table->bit)) {
>>> - old = features;
>>> - features = g_strdup_printf("%s%s%.46s", old, *old ? ", " :
>>> "",
>>> - table->name);
>>> - g_free(old);
>>> + if (features->len > 0) {
>>> + g_string_append(features, ", ");
>>> + }
>>> + g_string_append_printf(features, "%.46s",
>>> table->name);
>> We have a number of cases of this sort of idiom in the code base. I
>> wonder if it calls for a utility function:
>> qemu_append_with_sep(features, ", ", "%.46s", table->name)
>
> Good idea for https://wiki.qemu.org/Contribute/BiteSizedTasks
>
>> Anyway not mandatory for this patch so with the autoptr fix:
>> Reviewed-by: Alex Bennée <address@hidden>
>>
>>> mask &= ~(1ULL << table->bit);
>>> }
>>> }
>>> @@ -470,14 +469,15 @@ static void report_unsupported_feature(Error **errp,
>>> Qcow2Feature *table,
>>> }
>>> if (mask) {
>>> - old = features;
>>> - features = g_strdup_printf("%s%sUnknown incompatible feature: %"
>>> PRIx64,
>>> - old, *old ? ", " : "", mask);
>>> - g_free(old);
>>> + if (features->len > 0) {
>>> + g_string_append(features, ", ");
>>> + }
>>> + g_string_append_printf(features,
>>> + "Unknown incompatible feature: %" PRIx64,
>>> mask);
>>> }
>>> - error_setg(errp, "Unsupported qcow2 feature(s): %s",
>>> features);
>>> - g_free(features);
>>> + error_setg(errp, "Unsupported qcow2 feature(s): %s", features->str);
>>> + g_string_free(features, TRUE);
>>> }
>>> /*
>>
--
Alex Bennée