Is there any way to change the calling convention programmatically? I found some C++ code in this repo but wasn't able to successfully update it to 6.8.

static bool idaapi convert_to_usercall(void *ud)
    vdui_t &vu = *(vdui_t *)ud;
    if (!vu.cfunc)
        return false;
    if ( vu.cfunc->entry_ea == BADADDR )
        return false;
    tinfo_t type;
    qtype fields;       
    if (!vu.cfunc->get_func_type(type, fields))
        return false;
    func_type_info_t fti;
    int a = build_funcarg_info(idati, type.c_str(), fields.c_str(), &fti, 0);
    if (!convert_cc_to_special(fti))
        return false;
    build_func_type(&type, &fields, fti);
    if ( !apply_tinfo(idati, vu.cfunc->entry_ea, type.c_str(), fields.c_str(), 1) )
        return false;
    return true;

The code seems to use apis that are now deprecated or changed up. Does anybody know a way to fix up this code or some other approach.

Any help would be appreciated, whether it is C++ or Python.

2 Answers 2


SetType? An example in Python could be this:

SetType(func_ea, "int x(int arg1, char *arg2);")
  • Thanks for the response, but isn't there a way to set the calling convention explicitly? I want this task to be automated so I don't know know the function signature
    – ImCodezz
    Commented Jul 25, 2016 at 0:59
  • What I usually do is GetType, modify the returned prototype to set the __cdecl/__thiscall/__whatever calling conventiong and then issue a SetType call with the new string. Commented Jul 25, 2016 at 19:53

Ok, I found a solution in Python and it should work the same in C++. For anyone interested, here's the code. It changes the calling convention from __usercall to __fastcall:

old_func_type = idaapi.tinfo_t()

fi = idaapi.func_type_data_t()
if old_func_type.get_func_details(fi):
    if (fi.cc == idaapi.CM_CC_SPECIAL) or (fi.cc == idaapi.CM_CC_SPECIALE) or (fi.cc == idaapi.CM_CC_SPECIALP):
        fi.cc = idaapi.CM_CC_FASTCALL

        new_func_type = idaapi.tinfo_t()

        idaapi.apply_tinfo2(ea, new_func_type, idaapi.TINFO_DEFINITE)

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