compilation issues with sc_dt::sc_biguint data types (systemc)

Question

I'm facing an compilation issues with sc_dt::sc_biguint data types. I tried to reproduce the issue with a simple example below

#include<iostream>
#include<systemc.h>
using namespace std;

template<typename DATA_TYPE>
class base {
    public:
    void fun(DATA_TYPE ind){
    }

    void fun(std::string name){
    }
};

int sc_main(int argc, char* argv[]){
    base<uint64_t> b1;
    b1.fun(0);
    b1.fun("a");

    base<sc_dt::sc_biguint<128>> b2;
    b2.fun(0);
    b2.fun("a");
    return 0;
}

Here the call to overloaded function fun() is compiling fine for b1 which is using uint64_t as template. Also if I use uin8_t, uint16_t it compiles fine. But as soon as I use systemc data types (e.g. sc_biguint data type), I get the compilation errors like following

../test.cpp: In function ‘int sc_main(int, char**)’:
../test.cpp:21:13: error: call of overloaded ‘fun(int)’ is ambiguous
     b2.fun(0);
             ^
../test.cpp:8:10: note: candidate: void base<DATA_TYPE>::fun(DATA_TYPE) [with DATA_TYPE = sc_dt::sc_biguint<128>]
     void fun(DATA_TYPE ind){
          ^~~
../test.cpp:11:10: note: candidate: void base<DATA_TYPE>::fun(std::__cxx11::string) [with DATA_TYPE = sc_dt::sc_biguint<128>; std::__cxx11::string = std::__cxx11::basic_string<char>]
     void fun(std::string name){
          ^~~
../test.cpp:22:15: error: call of overloaded ‘fun(const char [2])’ is ambiguous
     b2.fun("a");
               ^
../test.cpp:8:10: note: candidate: void base<DATA_TYPE>::fun(DATA_TYPE) [with DATA_TYPE = sc_dt::sc_biguint<128>]
     void fun(DATA_TYPE ind){
          ^~~
../test.cpp:11:10: note: candidate: void base<DATA_TYPE>::fun(std::__cxx11::string) [with DATA_TYPE = sc_dt::sc_biguint<128>; std::__cxx11::string = std::__cxx11::basic_string<char>]
     void fun(std::string name){

sc_dt::sc_biguint<128> has the implicit conversion constructor sc_biguint( const sc_bv_base& v ) and sc_bv_base has the implicit conversion constructor sc_bv_base( const char* a );. You are unlucky. Perhaps, you need to specialize template<size_t N> class base<sc_dt::sc_biguint<N>>. — 3CEZVQ
– 3CEZVQ, Commented Jan 3 at 19:23

Red.Wave · Accepted Answer · 2025-01-03 19:25:30Z

The error message confirms an obvious problem in your program. For [DATA_TYPE = sc_dt::sc_biguint] the call to base::fun with raw character array input is ambiguous. Because apparently both std::string and sc_biguint have constructors accepting raw character arrays. Fixing that one is relatively simple: put in comstructed instances of either class:

using namespace std::literals;
b2.fun("a"s); /* UDL `s` is a shorthand for `std::string`*/
//shorten the typename first:
using bign128 = sc_dt::sc_biguint<128>;
b2.fun(bign128{"a"});

On the other hand, sc_biguint doesn't have any constructor that accepts an int as its input. And the sc_unsigned::sc_unsigned(int) is explicit. Its explicit instantiation must work:

b2.fun(sc_dt::sc_unsigned{0});

But this may not be what you expected from numeric comstant input. It looks to be preallocating some interal array to input size. A rational choice would be to default construct the big number; so it will automatically initialize to 0:

b2.fun(bign128{});

Always read the documentation and check the header file contents, before using any library. You may still be missing a lot of important stuff.

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