On 10/14/25 14:23, Peter Krempa wrote:
On Tue, Oct 14, 2025 at 08:31:46 +0200, Michal Privoznik via Devel wrote:
From: Michal Privoznik <mprivozn@redhat.com>
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/7f9c1f5f92c131354fc8b2b88d47... Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- 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)
Mind you, val_to_str_wmem() is available only in pre-4.6.0 era. https://gitlab.com/wireshark/wireshark/-/commit/84799be215313e61b83a3eaf074f... wireshark.git $ git describe --contains 84799be215313e61b83a3eaf074f89d6ee349b8c v4.6.0rc0~120 In this commit val_to_str_wmem() was renamed to val_to_str(). The whole point of these patches up to this one is to prepare for this change. Michal