Are std::string allowed within the compute region?

I have a C++ source code that uses String within the Class functions. I am having trouble with the Strings. I searched but could not find whether strings are allowed on GPU or not. For the illustration, I have created a small dummy program that re-generates the error. The program is given as follows.

#include <iostream>

class Dummy
      char* names;
      int row;
      int col;
      std::string mat_name;

      Dummy(int rows, int cols)
		   int i,j;
           row = rows;
           col = cols;
           names = new char[row*col];
           mat_name = "Sparse";
           #pragma acc enter data copyin(this)
           #pragma acc enter data create(names[0:row*col], mat_name)
           for(i=0; i<row; i++)
             for(j=0; j<col;j++)
                names[i*row + j] = 'A'+i+j;


        #pragma acc exit data delete(names[0:row*col], mat_name)
        #pragma acc exit data delete(this)
        delete [] names;
        names = nullptr;

      #pragma acc routine seq
      char get_mat_name()
          int res ="Sparse");
          if(res == 1)
            return 'd';
            return 'K';
      void Print()
         int i,j;
         for(i=0; i<row; i++)
             for(j=0; j<col;j++)
                std::cout << names[i*row + j];
              std::cout << std::endl;


int main()
    int row = 11;
    int col = 11;
    Dummy S1(row,col);

#pragma acc update device(S1.names[0:row*col], S1.mat_name)
#pragma acc parallel loop
   for(int i=0;i<row;i++)
		for(int j=0;j<col;j++)
            //Dummy operation to call a function that uses String
			S1.names[i*row+j] = S1.get_mat_name();

    std::cout << "Back from the device\n\n"<<std::endl;
#pragma acc update self(S1.names[0:row*col])
	std::cout<<"Exiting main()\n";


The error it generates is shown below.

     67, Generating update device(S1.mat_name,S1.names[:row*col])
         Generating NVIDIA GPU code
         71, #pragma acc loop gang /* blockIdx.x */
         72, #pragma acc loop seq
     67, Generating implicit copy(S1) [if not already present]
     71, Accelerator restriction: size of the GPU copy of S1.names is unknown
     72, Loop is parallelizable
     78, Generating update self(S1.names[:row*col])
Dummy::Dummy(int, int):
     20, Generating enter data copyin(this[:1])
         Generating enter data create(names[:col*row],mat_name)
     32, Generating exit data delete(mat_name,this[:1],names[:col*row])
NVC++-S-1061-Procedures called in a compute region must have acc routine information - std::basic_string<char, std::char_traits<char>, std::allocator<char>>::compare(const char *) const (main.cpp: 39)
     39, Accelerator restriction: call to 'std::basic_string<char, std::char_traits<char>, std::allocator<char>>::compare(const char *) const' with no acc routine information
NVC++/x86-64 Linux 23.1-0: compilation completed with severe errors

I am compiling the program using

nvc++ -acc -gpu=cc86,deepcopy -cpp -Mlarge_arrays -Minfo -o=main main.cpp

Any help will be appreciated.

I/O has very limited support on the device. And as such, strings aren’t supported either.

Hopefully in the future, unlikely anytime soon.


Thank you, Mat