For calls with return values, we emit a IsReturn parameter for it into __MIDL_ProcFormatString. During the INITOUT phase, client_do_args will try to read at this address. But we do not generate a _RetVal member for the _PARAM_STRUCTS types used by proxies, this means client_do_args will read out of bound.
* * *
An example is `IDispatchEx_RemoteInvokeEx_Proxy`
asan complaint:
``` 015c:0160:err:asan:asan_report ASan: read of 4 bytes at 015A88DC, caller 6A9A0EFA (__asan_report_load4_noabort, /home/shui/programs/wine/dlls/asan_dynamic_thunk/thunk.c:1031,1) 015c:0160:err:asan:asan_report stacktrace: 015c:0160:err:asan:asan_report 6A9A0EFA (__asan_report_load4_noabort, /home/shui/programs/wine/dlls/asan_dynamic_thunk/thunk.c:1031,1) 015c:0160:err:asan:asan_report 6A9ACB2C (client_do_args, /home/shui/programs/wine/dlls/rpcrt4/ndr_stubless.c:511,17) 015c:0160:err:asan:asan_report 6A9C5913 (ndr_client_call, /home/shui/programs/wine/dlls/rpcrt4/ndr_stubless.c:794,9) 015c:0160:err:asan:asan_report 6A965438 (NdrpClientCall2, /home/shui/programs/wine/dlls/rpcrt4/ndr_stubless.c:929,22) 015c:0160:err:asan:asan_report 6A916C77 (NdrClientCall2) 015c:0160:err:asan:asan_report 68662856 (IDispatchEx_RemoteInvokeEx_Proxy, dlls/dispex/i386-windows/disp_ex_p.c:82,15) 015c:0160:err:asan:asan_report 68661D6E (IDispatchEx_InvokeEx_Proxy, /home/shui/programs/wine/dlls/dispex/usrmarshal.c:100,10) 015c:0160:err:asan:asan_report 00401187 (IDispatchEx_InvokeEx, include/dispex.h:319,12) 015c:0160:err:asan:asan_report 00408F36 (test_dispex, /home/shui/programs/wine/dlls/dispex/tests/marshal.c:391,10) 015c:0160:err:asan:asan_report 004061FF (func_marshal, /home/shui/programs/wine/dlls/dispex/tests/marshal.c:433,5) 015c:0160:err:asan:asan_report 00407B60 (run_test, /home/shui/programs/wine/include/wine/test.h:794,9) 015c:0160:err:asan:asan_report 00407426 (main, /home/shui/programs/wine/include/wine/test.h:912,1) 015c:0160:err:asan:asan_report 0040767C (mainCRTStartup, /home/shui/programs/wine/dlls/msvcrt/crt_main.c:60,11) 015c:0160:err:asan:asan_report 7901FA24 (BaseThreadInitThunk) 015c:0160:err:asan:asan_report 7A50E0F7 (call_thread_func_wrapper) 015c:0160:err:asan:asan_report 7A5B6ADD (call_thread_func, /home/shui/programs/wine/dlls/ntdll/signal_i386.c:505,5) 015c:0160:err:asan:asan_report info: 015c:0160:err:asan:asan_report partial granule: 4 015c:0160:err:asan:asan_report stack-buffer-overflow, addr is 4 bytes to the right of the end of stack 015c:0160:err:asan:asan_report stack: [015A8820, 015A8860) 015c:0160:err:asan:asan_report stack pc: 6866252C (IDispatchEx_RemoteInvokeEx_Proxy, dlls/dispex/i386-windows/disp_ex_p.c:54,1), descr: 2 32 4 10 _RetVal:55 48 44 11 __params:69 ```
the parameters info:
``` 0024:trace:rpc:ndr_client_call INITOUT 0024:trace:rpc:client_do_args param[0]: 015EB834 type 08 IsIn IsBasetype 0024:trace:rpc:client_do_args param[1]: 015EB838 type 08 IsIn IsBasetype 0024:trace:rpc:client_do_args param[2]: 015EB83C type 08 IsIn IsBasetype 0024:trace:rpc:client_do_args param[3]: 015EB840 type 16 MustSize MustFree IsIn IsSimpleRef 0024:trace:rpc:client_do_args param[4]: 015EB844 type b4 MustSize MustFree IsOut IsSimpleRef ServerAllocSize = 16 0024:trace:rpc:client_do_args param[5]: 015EB848 type 1a MustSize MustFree IsOut IsSimpleRef ServerAllocSize = 32 0024:trace:rpc:client_do_args param[6]: 015EB84C type 2f MustSize MustFree IsIn 0024:trace:rpc:client_do_args param[7]: 015EB850 type 08 IsIn IsBasetype 0024:trace:rpc:client_do_args param[8]: 015EB854 type 1b MustSize MustFree IsIn IsSimpleRef 0024:trace:rpc:client_do_args param[9]: 015EB858 type 21 MustSize MustFree IsIn IsOut IsSimpleRef 0024:trace:rpc:client_do_args param[10]: 015EB85C type 08 IsOut IsReturn IsBasetype ```
reading of `param[10]` at `015EB85C`, which is the non-existent `_RetVal`, triggers the asan report.