diff --git a/src/fmelt.c b/src/fmelt.c
index f5184dd8f7..f54ba17fb0 100644
--- a/src/fmelt.c
+++ b/src/fmelt.c
@@ -441,7 +441,7 @@ SEXP getvaluecols(SEXP DT, SEXP dtnames, Rboolean valfactor, Rboolean verbose, s
           for (k=0; k<thislen; k++)
             REAL(target)[counter + k] = REAL(thiscol)[INTEGER(thisidx)[k]-1];
         } else {
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(thiscol), data->nrow*size);
+          memcpy((char *)REAL(target)+j*data->nrow*size, (char *)REAL(thiscol), data->nrow*size);
         }
         break;
         case INTSXP :
@@ -449,7 +449,7 @@ SEXP getvaluecols(SEXP DT, SEXP dtnames, Rboolean valfactor, Rboolean verbose, s
           for (k=0; k<thislen; k++)
             INTEGER(target)[counter + k] = INTEGER(thiscol)[INTEGER(thisidx)[k]-1];
         } else {
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(thiscol), data->nrow*size);
+          memcpy((char *)INTEGER(target)+j*data->nrow*size, (char *)INTEGER(thiscol), data->nrow*size);
         }
         break;
         case LGLSXP :
@@ -457,7 +457,7 @@ SEXP getvaluecols(SEXP DT, SEXP dtnames, Rboolean valfactor, Rboolean verbose, s
           for (k=0; k<thislen; k++)
             LOGICAL(target)[counter + k] = LOGICAL(thiscol)[INTEGER(thisidx)[k]-1];
         } else {
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(thiscol), data->nrow*size);
+          memcpy((char *)LOGICAL(target)+j*data->nrow*size, (char *)LOGICAL(thiscol), data->nrow*size);
         }
         break;
         default : error("Unknown column type '%s' for column '%s'.", type2char(TYPEOF(thiscol)), CHAR(STRING_ELT(dtnames, INTEGER(thisvaluecols)[i]-1)));
@@ -573,7 +573,7 @@ SEXP getidcols(SEXP DT, SEXP dtnames, Rboolean verbose, struct processData *data
         }
       } else {
         for (j=0; j<data->lmax; j++)
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(thiscol), data->nrow*size);
+          memcpy((char *)REAL(target)+j*data->nrow*size, (char *)REAL(thiscol), data->nrow*size);
       }
       break;
     case INTSXP :
@@ -587,7 +587,7 @@ SEXP getidcols(SEXP DT, SEXP dtnames, Rboolean verbose, struct processData *data
         }
       } else {
         for (j=0; j<data->lmax; j++)
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(thiscol), data->nrow*size);
+          memcpy((char *)INTEGER(target)+j*data->nrow*size, (char *)INTEGER(thiscol), data->nrow*size);
       }
       break;
     case LGLSXP :
@@ -601,7 +601,7 @@ SEXP getidcols(SEXP DT, SEXP dtnames, Rboolean verbose, struct processData *data
         }
       } else {
         for (j=0; j<data->lmax; j++)
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(thiscol), data->nrow*size);
+          memcpy((char *)LOGICAL(target)+j*data->nrow*size, (char *)LOGICAL(thiscol), data->nrow*size);
       }
       break;
     case STRSXP :
@@ -614,11 +614,12 @@ SEXP getidcols(SEXP DT, SEXP dtnames, Rboolean verbose, struct processData *data
           counter += thislen;
         }
       } else {
-        // SET_STRING_ELT for j=0 and memcpy for j>0, WHY?
-        // From assign.c's memcrecycle - only one SET_STRING_ELT per RHS item is needed to set generations (overhead)
-        for (k=0; k<data->nrow; k++) SET_STRING_ELT(target, k, STRING_ELT(thiscol, k));
-        for (j=1; j<data->lmax; j++)
-          memcpy((char *)DATAPTR(target)+j*data->nrow*size, (char *)DATAPTR(target), data->nrow*size);
+        const SEXP *s = STRING_PTR(thiscol);  // to reduce overhead of STRING_ELT() inside loop below. Read-only hence const.
+        for (j=0; j<data->lmax; j++) {
+          for (k=0; k<data->nrow; k++) {
+            SET_STRING_ELT(target, j*data->nrow + k, s[k]);
+          }
+        }
       }
       break;
     case VECSXP :
diff --git a/src/gsumm.c b/src/gsumm.c
index a5fa1946ef..419d0459e2 100644
--- a/src/gsumm.c
+++ b/src/gsumm.c
@@ -791,7 +791,7 @@ SEXP gmedian(SEXP x, SEXP narm) {
     isint64 = (isString(klass) && STRING_ELT(klass, 0) == char_integer64);
     ans = PROTECT(allocVector(REALSXP, ngrp));
     sub = PROTECT(allocVector(REALSXP, maxgrpn)); // allocate once upfront
-    ptr = DATAPTR(sub);
+    ptr = REAL(sub);
     if (!LOGICAL(narm)[0]) {
       for (i=0; i<ngrp; i++) {
         isna = FALSE;
@@ -876,7 +876,7 @@ SEXP gmedian(SEXP x, SEXP narm) {
   case LGLSXP: case INTSXP:
     ans = PROTECT(allocVector(REALSXP, ngrp));
     sub = PROTECT(allocVector(INTSXP, maxgrpn)); // allocate once upfront
-    ptr = DATAPTR(sub);
+    ptr = INTEGER(sub);
     if (!LOGICAL(narm)[0]) {
       for (i=0; i<ngrp; i++) {
         isna = FALSE;
diff --git a/src/rbindlist.c b/src/rbindlist.c
index 55475240a3..bec3fdd4e5 100644
--- a/src/rbindlist.c
+++ b/src/rbindlist.c
@@ -692,6 +692,10 @@ SEXP rbindlist(SEXP l, SEXP sexp_usenames, SEXP sexp_fill, SEXP idcol) {
         // TO DO: options(datatable.pedantic=TRUE) to issue this warning :
         // warning("Column %d of item %d is type '%s', inconsistent with column %d of item %d's type ('%s')",j+1,i+1,type2char(TYPEOF(thiscol)),j+1,first+1,type2char(TYPEOF(target)));
       }
+      if (TYPEOF(target)!=STRSXP && TYPEOF(thiscol)!=TYPEOF(target)) {
+        error("Internal error in rbindlist.c: type of 'thiscol' [%s] should have already been coerced to 'target' [%s]. please report to data.table issue tracker.",
+              type2char(TYPEOF(thiscol)), type2char(TYPEOF(target)));
+      }
       switch(TYPEOF(target)) {
       case STRSXP :
         isRowOrdered[resi] = FALSE;
@@ -723,22 +727,21 @@ SEXP rbindlist(SEXP l, SEXP sexp_usenames, SEXP sexp_fill, SEXP idcol) {
         }
         break;
       case VECSXP :
-        if (TYPEOF(thiscol) != VECSXP) error("Internal logical error in rbindlist.c (not VECSXP), please report to data.table issue tracker.");
         for (r=0; r<thislen; r++)
           SET_VECTOR_ELT(target, ansloc+r, VECTOR_ELT(thiscol,r));
         break;
       case CPLXSXP : // #1659 fix
-        if (TYPEOF(thiscol) != TYPEOF(target)) error("Internal logical error in rbindlist.c, type of 'thiscol' should have already been coerced to 'target'. please report to data.table issue tracker.");
         for (r=0; r<thislen; r++)
           COMPLEX(target)[ansloc+r] = COMPLEX(thiscol)[r];
         break;
       case REALSXP:
+        memcpy(REAL(target)+ansloc, REAL(thiscol), thislen*SIZEOF(thiscol));
+        break;
       case INTSXP:
+        memcpy(INTEGER(target)+ansloc, INTEGER(thiscol), thislen*SIZEOF(thiscol));
+        break;
       case LGLSXP:
-        if (TYPEOF(thiscol) != TYPEOF(target)) error("Internal logical error in rbindlist.c, type of 'thiscol' should have already been coerced to 'target'. please report to data.table issue tracker.");
-        memcpy((char *)DATAPTR(target) + ansloc * SIZEOF(thiscol),
-             (char *)DATAPTR(thiscol),
-             thislen * SIZEOF(thiscol));
+        memcpy(LOGICAL(target)+ansloc, LOGICAL(thiscol), thislen*SIZEOF(thiscol));
         break;
       default :
         error("Unsupported column type '%s'", type2char(TYPEOF(target)));
diff --git a/src/uniqlist.c b/src/uniqlist.c
index 20c9af506e..9c0d2318b1 100644
--- a/src/uniqlist.c
+++ b/src/uniqlist.c
@@ -55,7 +55,8 @@ SEXP uniqlist(SEXP l, SEXP order)
     int *o = INTEGER(order);  // only used when via_order is true
     switch(TYPEOF(v)) {
     case INTSXP : case LGLSXP : {
-      int *vd=INTEGER(v), prev, elem;
+      const int *vd=INTEGER(v);
+      int prev, elem;
       if (via_order) {
         // ad hoc by (order passed in)
         COMPARE1_VIA_ORDER COMPARE2
@@ -65,7 +66,8 @@ SEXP uniqlist(SEXP l, SEXP order)
       }
     } break;
     case STRSXP : {
-      SEXP *vd=(SEXP *)DATAPTR(v), prev, elem;   // TODO: tried to replace DATAPTR here but (SEXP *)&STRING_ELT(v,0) results in lvalue required as unary ‘&’ operand
+      const SEXP *vd=STRING_PTR(v);
+      SEXP prev, elem;
       if (via_order) {
         COMPARE1_VIA_ORDER && ENC2UTF8(elem)!=ENC2UTF8(prev) COMPARE2   // but most of the time they are equal, so ENC2UTF8 doesn't need to be called
       } else {
@@ -73,7 +75,8 @@ SEXP uniqlist(SEXP l, SEXP order)
       }
     } break;
     case REALSXP : {
-      uint64_t *vd=(uint64_t *)REAL(v), prev, elem;
+      const uint64_t *vd=(const uint64_t *)REAL(v);
+      uint64_t prev, elem;
       // grouping by integer64 makes sense (ids). grouping by float supported but a good use-case for that is harder to imagine
       if (getNumericRounding_C()==0 /*default*/ || inherits(v, "integer64")) {
         if (via_order) {