Missing function prototypes and wrong return types in `memory-hierarchy-riscv.c`

[phillipstanleymarbell]

Missing function prototypes and wrong return types in memory-hierarchy-riscv.c

memory-hierarchy-riscv.c:204:3: warning: implicit declaration of function ‘write_2’; did you mean ‘mwrite’? [-Wimplicit-function-declaration]
   write_2(S, data, &S->MEM[paddr - S->MEMBASE]);
   ^~~~~~~
   mwrite
memory-hierarchy-riscv.c: In function ‘riscVwritelong’:
memory-hierarchy-riscv.c:272:3: warning: implicit declaration of function ‘write_4’; did you mean ‘mwrite’? [-Wimplicit-function-declaration]
   write_4(S, data, &(S->MEM[paddr - S->MEMBASE]));
   ^~~~~~~
   mwrite
memory-hierarchy-riscv.c: In function ‘riscVreadbyte’:
memory-hierarchy-riscv.c:307:17: warning: ‘return’ with no value, in function returning non-void
                 return;
                 ^~~~~~
memory-hierarchy-riscv.c:290:1: note: declared here
 riscVreadbyte(Engine *E, State *S, ulong vaddr)
 ^~~~~~~~~~~~~
memory-hierarchy-riscv.c: In function ‘riscVreadword’:
memory-hierarchy-riscv.c:357:17: warning: ‘return’ with no value, in function returning non-void
                 return;
                 ^~~~~~
memory-hierarchy-riscv.c:340:1: note: declared here
 riscVreadword(Engine *E, State *S, ulong vaddr)
 ^~~~~~~~~~~~~
memory-hierarchy-riscv.c:377:3: warning: implicit declaration of function ‘read_2’; did you mean ‘mread’? [-Wimplicit-function-declaration]
   read_2(S, &S->MEM[paddr - S->MEMBASE], &data);
   ^~~~~~
   mread
memory-hierarchy-riscv.c: In function ‘riscVreadlong’:
memory-hierarchy-riscv.c:418:17: warning: ‘return’ with no value, in function returning non-void
                 return;
                 ^~~~~~
memory-hierarchy-riscv.c:401:1: note: declared here
 riscVreadlong(Engine *E, State *S, ulong vaddr)
 ^~~~~~~~~~~~~
memory-hierarchy-riscv.c:438:3: warning: implicit declaration of function ‘read_4’; did you mean ‘mread’? [-Wimplicit-function-declaration]
   read_4(S, &(S->MEM[paddr - S->MEMBASE]), &data);
   ^~~~~~
   mread