tinfo_calc_udt_aligns.py

#
# tinfo_calc_udt_aligns.py : Generate a struct type given a list of members with offsets
#

# First, create a simple uint32 tinfo.
uint32 = idaapi.tinfo_t()
uint32.create_simple_type(idaapi.BTF_UINT32)

# The udt_type_data_t struct holds information about struct types.
udt_data = idaapi.udt_type_data_t()

# This is the list of elements/members of the struct.
elems = [
    (0, "a", uint32),
    (4*8, "b", uint32),
    (12*8, "c", uint32)
]
        
for (offset, name, ty) in elems:
    udt_memb = udt_data.push_back()
    udt_memb.offset = offset
    udt_memb.type = ty
    udt_memb.size = udt_memb.type.get_size() << 3
    udt_memb.name = name
#endfor

# Set the size of the struct.
udt_data.total_size = 20

# Create the tinfo_t object.
tinfo = idaapi.tinfo_t()

# Turn it into a UDT using udt_data.
tinfo.create_udt(udt_data, idaapi.BTF_STRUCT)

# Ask IDA to use the provided offsets to generate the struct.
# If this returns True, then it means it succeeded.
tinfo.calc_udt_aligns()

str(tinfo)

# Output (formatted):
#
# struct __attribute__((aligned(4))) {
#   unsigned __int32 a;
#   unsigned __int32 b;
#   _BYTE gap8[4];
#   unsigned __int32 c;
#   _BYTE gap10[4];
# }