diff --git a/compat/zlib/contrib/minizip/crypt.h b/compat/zlib/contrib/minizip/crypt.h
index f4b93b78dc3..8bde464b61b 100644
--- a/compat/zlib/contrib/minizip/crypt.h
+++ b/compat/zlib/contrib/minizip/crypt.h
@@ -50,7 +50,7 @@ static int update_keys(unsigned long* pkeys, const z_crc_t* pcrc_32_tab, int c)
     (*(pkeys+1)) += (*(pkeys+0)) & 0xff;
     (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1;
     {
-      register int keyshift = (int)((*(pkeys+1)) >> 24);
+      int keyshift = (int)((*(pkeys+1)) >> 24);
       (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift);
     }
     return c;
diff --git a/libtommath/bn_mp_div.c b/libtommath/bn_mp_div.c
index 71de55beaeb..bca227d6af5 100644
--- a/libtommath/bn_mp_div.c
+++ b/libtommath/bn_mp_div.c
@@ -31,7 +31,7 @@ mp_err mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
    }
 
    /* init our temps */
-   if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
+   if ((err = mp_init_multi(&ta, &tb, &tq, &q, (void *)NULL)) != MP_OKAY) {
       return err;
    }
 
@@ -64,7 +64,7 @@ mp_err mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
       d->sign = MP_IS_ZERO(d) ? MP_ZPOS : n;
    }
 LBL_ERR:
-   mp_clear_multi(&ta, &tb, &tq, &q, NULL);
+   mp_clear_multi(&ta, &tb, &tq, &q, (void *)NULL);
    return err;
 }
 
diff --git a/libtommath/bn_s_mp_balance_mul.c b/libtommath/bn_s_mp_balance_mul.c
index 7ece5d79427..557cc1d292d 100644
--- a/libtommath/bn_s_mp_balance_mul.c
+++ b/libtommath/bn_s_mp_balance_mul.c
@@ -19,7 +19,7 @@ mp_err s_mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c)
    if ((err = mp_init_size(&a0, bsize + 2)) != MP_OKAY) {
       return err;
    }
-   if ((err = mp_init_multi(&tmp, &r, NULL)) != MP_OKAY) {
+   if ((err = mp_init_multi(&tmp, &r, (void *)NULL)) != MP_OKAY) {
       mp_clear(&a0);
       return err;
    }
@@ -75,7 +75,7 @@ mp_err s_mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c)
 
    mp_exch(&r,c);
 LBL_ERR:
-   mp_clear_multi(&a0, &tmp, &r,NULL);
+   mp_clear_multi(&a0, &tmp, &r, (void *)NULL);
    return err;
 }
 #endif
diff --git a/libtommath/bn_s_mp_toom_mul.c b/libtommath/bn_s_mp_toom_mul.c
index 86901b074c3..c7db3a599d9 100644
--- a/libtommath/bn_s_mp_toom_mul.c
+++ b/libtommath/bn_s_mp_toom_mul.c
@@ -36,7 +36,7 @@ mp_err s_mp_toom_mul(const mp_int *a, const mp_int *b, mp_int *c)
    mp_err err;
 
    /* init temps */
-   if ((err = mp_init_multi(&S1, &S2, &T1, NULL)) != MP_OKAY) {
+   if ((err = mp_init_multi(&S1, &S2, &T1, (void *)NULL)) != MP_OKAY) {
       return err;
    }
 
@@ -208,7 +208,7 @@ mp_err s_mp_toom_mul(const mp_int *a, const mp_int *b, mp_int *c)
 LBL_ERRa1:
    mp_clear(&a0);
 LBL_ERRa0:
-   mp_clear_multi(&S1, &S2, &T1, NULL);
+   mp_clear_multi(&S1, &S2, &T1, (void *)NULL);
    return err;
 }
 
diff --git a/unix/dltest/pkgb.c b/unix/dltest/pkgb.c
index b221518b0a9..75d1eac1e1a 100644
--- a/unix/dltest/pkgb.c
+++ b/unix/dltest/pkgb.c
@@ -56,7 +56,7 @@ Pkgb_SubObjCmd(
 	    || (Tcl_GetIntFromObj(interp, objv[2], &second) != TCL_OK)) {
 	char buf[TCL_INTEGER_SPACE];
 	snprintf(buf, sizeof(buf), "%d", Tcl_GetErrorLine(interp));
-	Tcl_AppendResult(interp, " in line: ", buf, NULL);
+	Tcl_AppendResult(interp, " in line: ", buf, (void *)NULL);
 	return TCL_ERROR;
     }
     Tcl_SetObjResult(interp, Tcl_NewIntObj(first - second));
diff --git a/unix/dltest/pkgooa.c b/unix/dltest/pkgooa.c
index aed89fed655..6a78692c0de 100644
--- a/unix/dltest/pkgooa.c
+++ b/unix/dltest/pkgooa.c
@@ -108,18 +108,18 @@ Pkgooa_Init(
     }
     if (tclStubsPtr == NULL) {
 	Tcl_AppendResult(interp, "Tcl stubs are not initialized, "
-		"did you compile using -DUSE_TCL_STUBS? ", NULL);
+		"did you compile using -DUSE_TCL_STUBS? ", (void *)NULL);
 	return TCL_ERROR;
     }
     if (Tcl_OOInitStubs(interp) == NULL) {
 	return TCL_ERROR;
     }
     if (tclOOStubsPtr == NULL) {
-	Tcl_AppendResult(interp, "TclOO stubs are not initialized", NULL);
+	Tcl_AppendResult(interp, "TclOO stubs are not initialized", (void *)NULL);
 	return TCL_ERROR;
     }
     if (tclOOIntStubsPtr == NULL) {
-	Tcl_AppendResult(interp, "TclOO internal stubs are not initialized", NULL);
+	Tcl_AppendResult(interp, "TclOO internal stubs are not initialized", (void *)NULL);
 	return TCL_ERROR;
     }