On Tue, Oct 14, 2025 at 08:31:46 +0200, Michal Privoznik via Devel wrote:
> From: Michal Privoznik <[email protected]>
>
> One of the problems of using val_to_str() is that it may return a
> const string from given table ('vs'), OR return an allocated one.
> Since the caller has no idea which case it is, it resides to safe
> option and don't free returned string. But that might lead to a
> memleak. This behaviour is fixed with wireshark-4.6.0 and support
> for it will be introduced soon. But first, make vir_val_to_str()
> behave like fixed val_to_str() from newer wireshark: just always
> allocate the string.
>
> Now, if val_to_str() needs to allocate new memory it obtains
> allocator by calling wmem_packet_scope() which is what we may do
> too.
>
> Hand in hand with that, we need to free the memory using the
> correct allocator, hence wmem_free(). But let's put it into a
> wrapper vir_wmem_free() because just like val_to_str(), it'll
> need additional argument when adapting to new wireshark.
>
> Oh, and freeing the memory right after col_add_fstr() is safe as
> it uses vsnprintf() under the hood to format passed args.
>
> One last thing, the wmem.h file used to live under epan/wmem/ but
> then in v3.5.0~240 [1] was moved to wsutil/wmem/.
>
> 1:
> https://gitlab.com/wireshark/wireshark/-/commit/7f9c1f5f92c131354fc8b2b88d473706786064c0
> Signed-off-by: Michal Privoznik <[email protected]>
> ---
> meson.build | 20 ++++++++++++++++
> tools/wireshark/src/meson.build | 1 +
> tools/wireshark/src/packet-libvirt.c | 35 ++++++++++++++++++++++------
> 3 files changed, 49 insertions(+), 7 deletions(-)
[...]
> @@ -140,13 +145,19 @@ static const value_string status_strings[] = {
> { -1, NULL }
> };
>
> -static const char *
> +static char *
> G_GNUC_PRINTF(3, 0)
> vir_val_to_str(const uint32_t val,
> const value_string *vs,
> const char *fmt)
> {
> - return val_to_str(val, vs, fmt);
> + return val_to_str_wmem(wmem_packet_scope(), val, vs, fmt);
I didn't try building this but grepping in the wireshark code base shows
only:
wsutil/value_string.h:rval_to_str_wmem(wmem_allocator_t* scope, const uint32_t
val, const range_string *rs, const char *fmt)
wsutil/value_string.h:bytesval_to_str_wmem(wmem_allocator_t* scope, const
uint8_t *val, const size_t val_len, const bytes_string *bs, const char *fmt)
