[tamird:b4/bpf-ringbuf-callback 10/11] ringbuf.c:412:9: error: ISO C90 forbids mixed declarations and code

[kernel test robot <lkp@intel.com>]

tree:   https://github.com/tamird/linux b4/bpf-ringbuf-callback
head:   60bd75d7c79a01786dd5da0b5264a58fc5a3c3be
commit: 669fde8241bd5bb91c22df6640b243ca1da272b9 [10/11] libbpf: ringbuf: Add a caller-owned iterator
config: arm-randconfig-004 (https://download.01.org/0day-ci/archive/20260615/202606150201.QBTLSmit-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 13.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260615/202606150201.QBTLSmit-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202606150201.QBTLSmit-lkp@intel.com/

All errors (new ones prefixed by >>):

   ringbuf.c: In function 'ringbuf_process_ring':
>> ringbuf.c:412:9: error: ISO C90 forbids mixed declarations and code [-Werror=declaration-after-statement]
     412 |         struct ring_buffer_iter it
         |         ^~~~~~
   cc1: all warnings being treated as errors
   make[6]: *** [tools/build/Makefile.build:95: tools/bpf/resolve_btfids/libbpf/staticobjs/ringbuf.o] Error 1 shuffle=1351407704
   make[6]: Target '__build' not remade because of errors.
   make[5]: *** [Makefile:152: tools/bpf/resolve_btfids/libbpf/staticobjs/libbpf-in.o] Error 2 shuffle=1351407704
   make[5]: Target 'tools/bpf/resolve_btfids/libbpf/libbpf.a' not remade because of errors.
   make[4]: *** [Makefile:62: tools/bpf/resolve_btfids//libbpf/libbpf.a] Error 2 shuffle=1351407704
   make[4]: Target 'all' not remade because of errors.
   make[3]: *** [Makefile:77: bpf/resolve_btfids] Error 2 shuffle=1351407704
   make[2]: *** [Makefile:1557: tools/bpf/resolve_btfids] Error 2 shuffle=1351407704
   make[2]: Target 'prepare' not remade because of errors.
   make[1]: *** [Makefile:248: __sub-make] Error 2 shuffle=1351407704
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2 shuffle=1351407704
   make: Target 'prepare' not remade because of errors.

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