Unable to redefine low-level library function

I am using the template from Redefining low-level library functions to enable direct use of high-level library functions in the C library (can get you code embedder to work)

namespace std{
struct __FILE
{ int handle;};

FILE __stdout;
FILE __stdin;
FILE __stderr;

int fgetc(FILE *f){
int c;
c = uart_read();
if(c =='\r'){
uart_write(c);
c = '\n';
}
uart_write(c);
return c;
}

int fputc(int c, FILE *stream){
return uart_write(c);
}

int ferror(FILE *stream){
return 1;
}


long int ftell(FILE *stream){
return 1;

}
int fclose(FILE *f){
return 1;
}
int fseek(FILE *f, long nPos, int nMode){
return 0;
}

int fflush(FILE *f){
return 1;
}

}

With the following header,

#ifndef __UART_H

#define __UART_H

#include "stm32f4xx.h"

#include <stdio.h>

// a whole load of function declarations

#endif

The compiler throws the following error,

error: redefinition of __FILE

struct __FILE

I using:

uVision V5.41.0.0

ArmClang V6.22

Target board - ST's NUF411RE

I have seen that this question has been posed before but the answer given in those cases was just to point to the Arm 5 to 6 compiler mitigation document

I cant find the solution to this in there.