diff --git a/tgt-vvp/draw_ufunc.c b/tgt-vvp/draw_ufunc.c
index db5ee7dcd..6860b8531 100644
--- a/tgt-vvp/draw_ufunc.c
+++ b/tgt-vvp/draw_ufunc.c
@@ -112,6 +112,15 @@ struct vector_info draw_ufunc_expr(ivl_expr_t exp, unsigned wid)
 
       res.base = allocate_vector(wid);
       res.wid  = wid;
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits for function result.\n",
+		    ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+	    return res;
+      }
+
+      assert(res.base != 0);
 
       unsigned load_wid = swid;
       if (load_wid > ivl_signal_width(retval))
diff --git a/tgt-vvp/draw_vpi.c b/tgt-vvp/draw_vpi.c
index 4a0ded932..43821385f 100644
--- a/tgt-vvp/draw_vpi.c
+++ b/tgt-vvp/draw_vpi.c
@@ -303,6 +303,13 @@ struct vector_info draw_vpi_func_call(ivl_expr_t fnet, unsigned wid)
 
       res.base = allocate_vector(wid);
       res.wid  = wid;
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits for system function result.\n",
+		    ivl_expr_file(fnet), ivl_expr_lineno(fnet), wid);
+	    vvp_errors += 1;
+      }
+
       sprintf(call_string, "    %%vpi_func %u %u \"%s\", %u, %u",
               ivl_file_table_index(ivl_expr_file(fnet)),
 	      ivl_expr_lineno(fnet), ivl_expr_name(fnet), res.base, res.wid);
diff --git a/tgt-vvp/eval_expr.c b/tgt-vvp/eval_expr.c
index 85300588d..63dabb04a 100644
--- a/tgt-vvp/eval_expr.c
+++ b/tgt-vvp/eval_expr.c
@@ -277,6 +277,14 @@ static struct vector_info draw_eq_immediate(ivl_expr_t exp, unsigned ewid,
 	   expressions. */
       if (lv.base < 8) {
 	    unsigned base = allocate_vector(ewid);
+	    if (base == 0) {
+		  fprintf(stderr, "%s:%u: vvp.tgt error: "
+			  "Unable to allocate %u thread bits "
+			  "for result of equality compare.\n",
+			  ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+		  vvp_errors += 1;
+	    }
+
 	    fprintf(vvp_out, "    %%mov %u, %u, 1;\n", base, lv.base);
 	    lv.base = base;
 	    lv.wid = ewid;
@@ -285,6 +293,14 @@ static struct vector_info draw_eq_immediate(ivl_expr_t exp, unsigned ewid,
 
       } else if (lv.wid < ewid) {
 	    unsigned base = allocate_vector(ewid);
+	    if (base == 0) {
+		  fprintf(stderr, "%s:%u: vvp.tgt error: "
+			  "Unable to allocate %u thread bits "
+			  "for result of equality compare.\n",
+			  ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+		  vvp_errors += 1;
+	    }
+
 	    if (lv.base >= 8)
 		  clr_vector(lv);
 	    fprintf(vvp_out, "    %%mov %u, %u, %u;\n", base,
@@ -309,6 +325,7 @@ static struct vector_info draw_binary_expr_eq_real(ivl_expr_t exp)
 
       res.base = allocate_vector(1);
       res.wid  = 1;
+      assert(res.base);
 
       lword = draw_eval_real(ivl_expr_oper1(exp));
       rword = draw_eval_real(ivl_expr_oper2(exp));
@@ -441,6 +458,14 @@ static struct vector_info draw_binary_expr_eq(ivl_expr_t exp,
 	   uses. This is because that bit may be clobbered by other
 	   expressions. */
       { unsigned base = allocate_vector(ewid);
+	if (base == 0) {
+	      fprintf(stderr, "%s:%u: vvp.tgt error: "
+		      "Unable to allocate %u thread bits "
+		      "for result of equality compare.\n",
+		      ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+	}
+
         fprintf(vvp_out, "    %%mov %u, %u, 1;\n", base, lv.base);
 	lv.base = base;
 	lv.wid = ewid;
@@ -467,6 +492,7 @@ static struct vector_info draw_binary_expr_land(ivl_expr_t exp, unsigned wid)
 	    clr_vector(lv);
 	    tmp.base = allocate_vector(1);
 	    tmp.wid = 1;
+	    assert(tmp.base);
 	    fprintf(vvp_out, "    %%or/r %u, %u, %u;\n", tmp.base,
 		    lv.base, lv.wid);
 	    lv = tmp;
@@ -478,6 +504,7 @@ static struct vector_info draw_binary_expr_land(ivl_expr_t exp, unsigned wid)
 	    clr_vector(rv);
 	    tmp.base = allocate_vector(1);
 	    tmp.wid = 1;
+	    assert(tmp.base);
 	    fprintf(vvp_out, "    %%or/r %u, %u, %u;\n", tmp.base,
 		    rv.base, rv.wid);
 	    rv = tmp;
@@ -514,6 +541,14 @@ static struct vector_info draw_binary_expr_land(ivl_expr_t exp, unsigned wid)
 
 	/* Write the result into a zero-padded result. */
       { unsigned base = allocate_vector(wid);
+	if (base == 0) {
+	      fprintf(stderr, "%s:%u: vvp.tgt error: "
+		      "Unable to allocate %u thread bits "
+		      "for result of padded logical AND.\n",
+		      ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	      vvp_errors += 1;
+	}
+
         fprintf(vvp_out, "    %%mov %u, %u, 1;\n", base, lv.base);
 	clr_vector(lv);
 	lv.base = base;
@@ -541,6 +576,7 @@ static struct vector_info draw_binary_expr_lor(ivl_expr_t exp, unsigned wid)
 	    clr_vector(lv);
 	    tmp.base = allocate_vector(1);
 	    tmp.wid = 1;
+	    assert(tmp.base);
 	    fprintf(vvp_out, "    %%or/r %u, %u, %u;\n", tmp.base,
 		    lv.base, lv.wid);
 	    lv = tmp;
@@ -555,6 +591,7 @@ static struct vector_info draw_binary_expr_lor(ivl_expr_t exp, unsigned wid)
 	    clr_vector(rv);
 	    tmp.base = allocate_vector(1);
 	    tmp.wid = 1;
+	    assert(tmp.base);
 	    fprintf(vvp_out, "    %%or/r %u, %u, %u;\n", tmp.base,
 		    rv.base, rv.wid);
 	    rv = tmp;
@@ -592,6 +629,14 @@ static struct vector_info draw_binary_expr_lor(ivl_expr_t exp, unsigned wid)
 
 	/* Write the result into a zero-padded result. */
       { unsigned base = allocate_vector(wid);
+	if (base == 0) {
+	      fprintf(stderr, "%s:%u: vvp.tgt error: "
+		      "Unable to allocate %u thread bits "
+		      "for result of padded logical OR.\n",
+		      ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	      vvp_errors += 1;
+	}
+
         fprintf(vvp_out, "    %%mov %u, %u, 1;\n", base, lv.base);
 	clr_vector(lv);
 	lv.base = base;
@@ -615,6 +660,8 @@ static struct vector_info draw_binary_expr_le_real(ivl_expr_t exp)
       res.base = allocate_vector(1);
       res.wid  = 1;
 
+      assert(res.base);
+
       clr_word(lword);
       clr_word(rword);
 
@@ -695,6 +742,14 @@ static struct vector_info draw_binary_expr_le_bool(ivl_expr_t exp,
 	   uses. This is because that bit may be clobbered by other
 	   expressions. */
       { unsigned base = allocate_vector(wid);
+	if (base == 0) {
+	      fprintf(stderr, "%s:%u: vvp.tgt error: "
+		      "Unable to allocate %u thread bits "
+		      "for result of padded inequality compare.\n",
+		      ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	      vvp_errors += 1;
+	}
+
         fprintf(vvp_out, "    %%mov %u, 5, 1;\n", base);
 	tmp.base = base;
 	tmp.wid = wid;
@@ -822,6 +877,14 @@ static struct vector_info draw_binary_expr_le(ivl_expr_t exp,
 	   uses. This is because that bit may be clobbered by other
 	   expressions. */
       { unsigned base = allocate_vector(wid);
+	if (base == 0) {
+	      fprintf(stderr, "%s:%u: vvp.tgt error: "
+		      "Unable to allocate %u thread bits "
+		      "for result of padded inequality compare.\n",
+		      ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	      vvp_errors += 1;
+	}
+
         fprintf(vvp_out, "    %%mov %u, 5, 1;\n", base);
 	lv.base = base;
 	lv.wid = wid;
@@ -858,6 +921,14 @@ static struct vector_info draw_binary_expr_logic(ivl_expr_t exp,
 		  struct vector_info tmp;
 		  tmp.base = allocate_vector(lv.wid);
 		  tmp.wid = lv.wid;
+		  if (tmp.base == 0) {
+			fprintf(stderr, "%s:%u: vvp.tgt error: "
+				"Unable to allocate %u thread bits "
+				"for result of binary logic.\n",
+				ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+			vvp_errors += 1;
+		  }
+
 		  fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 			  tmp.base, lv.base, tmp.wid);
 		  lv = tmp;
@@ -933,6 +1004,14 @@ static struct vector_info draw_binary_expr_lrs(ivl_expr_t exp, unsigned wid)
 		  struct vector_info tmp;
 		  tmp.base = allocate_vector(lv.wid);
 		  tmp.wid = lv.wid;
+		  if (tmp.base == 0) {
+			fprintf(stderr, "%s:%u: vvp.tgt error: "
+				"Unable to allocate %u thread bits "
+				"for result of left shift (<<).\n",
+				ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+			vvp_errors += 1;
+		  }
+
 		  fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 			  tmp.base, lv.base, lv.wid);
 		  lv = tmp;
@@ -960,6 +1039,14 @@ static struct vector_info draw_binary_expr_lrs(ivl_expr_t exp, unsigned wid)
 		  struct vector_info tmp;
 		  tmp.base = allocate_vector(lv.wid);
 		  tmp.wid = lv.wid;
+		  if (tmp.base == 0) {
+			fprintf(stderr, "%s:%u: vvp.tgt error: "
+				"Unable to allocate %u thread bits "
+				"for result of right shift (>>).\n",
+				ivl_expr_file(exp), ivl_expr_lineno(exp), lv.wid);
+			vvp_errors += 1;
+		  }
+
 		  fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 			  tmp.base, lv.base, lv.wid);
 		  lv = tmp;
@@ -992,6 +1079,14 @@ static struct vector_info draw_binary_expr_lrs(ivl_expr_t exp, unsigned wid)
 		  struct vector_info tmp;
 		  tmp.base = allocate_vector(lv.wid);
 		  tmp.wid = lv.wid;
+		  if (tmp.base == 0) {
+			fprintf(stderr, "%s:%u: vvp.tgt error: "
+				"Unable to allocate %u thread bits "
+				"for result of right shift (>>>).\n",
+				ivl_expr_file(exp), ivl_expr_lineno(exp), lv.wid);
+			vvp_errors += 1;
+		  }
+
 		  fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 			  tmp.base, lv.base, lv.wid);
 		  lv = tmp;
@@ -1030,6 +1125,13 @@ static struct vector_info draw_load_add_immediate(ivl_expr_t le,
       imm = get_number_immediate(re);
       lv.base = allocate_vector(wid);
       lv.wid = wid;
+      if (lv.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "for result of addition.\n",
+		    ivl_expr_file(le), ivl_expr_lineno(le), wid);
+	    vvp_errors += 1;
+      }
 
 	/* Load the signal value with a %load that adds the index
 	   register to the value being loaded. */
@@ -1093,6 +1195,14 @@ static struct vector_info draw_sub_immediate(ivl_expr_t le,
 	  case 0:
 	  case 1:
 	    tmp = allocate_vector(wid);
+	    if (tmp == 0) {
+		  fprintf(stderr, "%s:%u: vvp.tgt error: "
+			  "Unable to allocate %u thread bits "
+			  "for result of subtraction.\n",
+			  ivl_expr_file(le), ivl_expr_lineno(le), wid);
+		  vvp_errors += 1;
+	    }
+
 	    fprintf(vvp_out, "    %%mov %u, %u, %u;\n", tmp, lv.base, wid);
 	    lv.base = tmp;
 	    fprintf(vvp_out, "    %%subi %u, %lu, %u;\n", lv.base, imm, wid);
@@ -1205,6 +1315,14 @@ static struct vector_info draw_binary_expr_arith(ivl_expr_t exp, unsigned wid)
 
 	    tmp.base = allocate_vector(wid);
 	    tmp.wid = wid;
+	    if (tmp.base == 0) {
+		  fprintf(stderr, "%s:%u: vvp.tgt error: "
+			  "Unable to allocate %u thread bits "
+			  "for result of arithmetic expression.\n",
+			  ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+		  vvp_errors += 1;
+	    }
+
 	    fprintf(vvp_out, "    %%mov %u, %u, %u;\n", tmp.base,
 		    lv.base, wid);
 	    lv = tmp;
@@ -1343,6 +1461,14 @@ static struct vector_info draw_concat_expr(ivl_expr_t exp, unsigned wid,
 	/* Allocate a vector to hold the result. */
       res.base = allocate_vector(wid);
       res.wid = wid;
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "for result of concatenation.\n",
+		    ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+      }
+
 
 	/* Get the repeat count. This must be a constant that has been
 	   evaluated at compile time. The operands will be repeated to
@@ -1464,6 +1590,13 @@ static struct vector_info draw_number_expr(ivl_expr_t exp, unsigned wid)
 	   vector. Allocate the vector and use %mov instructions to
 	   load the constant bit values. */
       res.base = allocate_vector(wid);
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "for number value.\n",
+		    ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+      }
 
       if ((!number_is_unknown(exp)) && number_is_immediate(exp, 16)) {
 	    int val = get_number_immediate(exp);
@@ -1546,6 +1679,13 @@ static struct vector_info draw_pad_expr(ivl_expr_t exp, unsigned wid)
 
       res.base = allocate_vector(wid);
       res.wid = wid;
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "to pad expression.\n",
+		    ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+      }
 
       fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 	      res.base, subv.base, subv.wid);
@@ -1580,6 +1720,7 @@ static struct vector_info draw_realnum_expr(ivl_expr_t exp, unsigned wid)
 
       res.base = allocate_vector(wid);
       res.wid = wid;
+      assert(res.base);
 
       addr = res.base;
       run = 1;
@@ -1666,6 +1807,13 @@ static struct vector_info draw_string_expr(ivl_expr_t exp, unsigned wid)
 	   vector. Allocate the vector and use %mov instructions to
 	   load the constant bit values. */
       res.base = allocate_vector(wid);
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "for string value.\n",
+		    ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+      }
 
 	/* Since this is a string, we know that all the bits are
 	   defined and each character represents exactly 8 bits. Use
@@ -1819,6 +1967,14 @@ static struct vector_info draw_signal_expr(ivl_expr_t exp, unsigned wid,
 
       res.base = allocate_vector(wid);
       res.wid  = wid;
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "to load variable/wire.\n",
+		    ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+	    vvp_errors += 1;
+      }
+
       save_expression_lookaside(res.base, exp, wid);
 
       draw_signal_dest(exp, res, -1, 0L);
@@ -1846,6 +2002,13 @@ static struct vector_info draw_select_array(ivl_expr_t sube,
 
       res.base = allocate_vector(wid);
       res.wid = wid;
+      if (res.base == 0) {
+	    fprintf(stderr, "%s:%u: vvp.tgt error: "
+		    "Unable to allocate %u thread bits "
+		    "to hold selected value.\n",
+		    ivl_expr_file(sube), ivl_expr_lineno(sube), wid);
+	    vvp_errors += 1;
+      }
 
       for (idx = 0 ;  idx < wid ;  idx += 1) {
 	    fprintf(vvp_out, "  %%load/avx.p %u, v%p, 0;\n", res.base+idx, sig);
@@ -1891,6 +2054,7 @@ static struct vector_info draw_select_signal(ivl_expr_t sube,
 
 	    res.base = allocate_vector(wid);
 	    res.wid = wid;
+	    assert(res.base);
 	    fprintf(vvp_out, "   %%load/v %u, v%p_%u, %u; Only need %u of %u bits\n",
 		    res.base, sig, use_word, bit_wid, bit_wid, ivl_expr_width(sube));
  
@@ -1907,6 +2071,7 @@ static struct vector_info draw_select_signal(ivl_expr_t sube,
 	/* Alas, do it the hard way. */
       res.base = allocate_vector(wid);
       res.wid = wid;
+      assert(res.base);
 
       for (idx = 0 ;  idx < res.wid ;  idx += 1) {
 	    if (idx >= bit_wid) {
@@ -1981,6 +2146,7 @@ static struct vector_info draw_select_expr(ivl_expr_t exp, unsigned wid,
       if (subv.base < 4) {
 	    res.base = allocate_vector(subv.wid);
 	    res.wid = subv.wid;
+	    assert(res.base);
 	    fprintf(vvp_out, "    %%mov %u, %u, %u;\n", res.base,
 		    subv.base, res.wid);
 	    subv = res;
@@ -2051,6 +2217,7 @@ static struct vector_info draw_ternary_expr(ivl_expr_t exp, unsigned wid)
 	    struct vector_info tmp;
 	    tmp.base = allocate_vector(wid);
 	    tmp.wid = wid;
+	    assert(tmp.base);
 	    fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 		    tmp.base, tru.base, wid);
 	    tru = tmp;
@@ -2108,6 +2275,7 @@ static struct vector_info draw_sfunc_expr(ivl_expr_t exp, unsigned wid)
 		   || ivl_expr_value(exp) == IVL_VT_BOOL);
 	    res.base = allocate_vector(wid);
 	    res.wid  = wid;
+	    assert(res.base);
 	    fprintf(vvp_out, "    %%vpi_func %u %u \"%s\", %u, %u;\n",
 		    ivl_file_table_index(ivl_expr_file(exp)),
 		    ivl_expr_lineno(exp), ivl_expr_name(exp),
@@ -2221,6 +2389,14 @@ static struct vector_info draw_unary_expr(ivl_expr_t exp, unsigned wid)
 		  struct vector_info tmp;
 		  tmp.base = allocate_vector(wid);
 		  tmp.wid = wid;
+		  if (tmp.base == 0) {
+			fprintf(stderr, "%s:%u: vvp.tgt error: "
+				"Unable to allocate %u thread bits "
+				"to pad unary expression result.\n",
+				ivl_expr_file(exp), ivl_expr_lineno(exp), wid);
+			vvp_errors += 1;
+		  }
+
 		  fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 			  tmp.base, res.base, res.wid);
 		  fprintf(vvp_out, "    %%mov %u, 0, %u;\n",
@@ -2246,6 +2422,7 @@ static struct vector_info draw_unary_expr(ivl_expr_t exp, unsigned wid)
 		  if (res.base < 4) {
 			tmp.base = allocate_vector(res.wid);
 			tmp.wid = res.wid;
+			assert(res.base);
 			fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 				tmp.base, res.base, res.wid);
 			res = tmp;
@@ -2269,6 +2446,7 @@ static struct vector_info draw_unary_expr(ivl_expr_t exp, unsigned wid)
 		  struct vector_info tmp;
 		  tmp.base = allocate_vector(wid);
 		  tmp.wid = wid;
+		  assert(res.base);
 		  fprintf(vvp_out, "    %%mov %u, %u, %u;\n",
 			  tmp.base, res.base, res.wid);
 		  fprintf(vvp_out, "    %%mov %u, 0, %u;\n",
diff --git a/tgt-vvp/vector.c b/tgt-vvp/vector.c
index 2c1d5012d..77f08ec96 100644
--- a/tgt-vvp/vector.c
+++ b/tgt-vvp/vector.c
@@ -91,6 +91,9 @@ static unsigned allocate_vector_no_lookaside(unsigned wid, int skip_lookaside)
       unsigned idx = 0;
 
       while (idx < wid) {
+	    if (base+idx >= MAX_VEC)
+		  return 0;
+
 	    assert((base + idx) < MAX_VEC);
 	    if ((allocation_map[base+idx].alloc > 0)
 		|| (skip_lookaside && peek_exp(base+idx))) {
@@ -121,6 +124,9 @@ static unsigned allocate_vector_no_lookaside(unsigned wid, int skip_lookaside)
  * again without worrying about trashing lookaside results. This
  * should lead to preferentially allocating new bits instead of
  * constantly overwriting intermediate results.
+ *
+ * If there is no space for a vector of the given width, then give up
+ * and return 0.
  */
 unsigned allocate_vector(unsigned wid)
 {
diff --git a/tgt-vvp/vvp.c b/tgt-vvp/vvp.c
index 37aab78f6..e1cb632f3 100644
--- a/tgt-vvp/vvp.c
+++ b/tgt-vvp/vvp.c
@@ -27,6 +27,7 @@
 # include  <sys/stat.h>
 
 FILE*vvp_out = 0;
+int vvp_errors = 0;
 
 inline static void draw_execute_header(ivl_design_t des)
 {
@@ -79,6 +80,8 @@ int target_design(ivl_design_t des)
 	    return -1;
       }
 
+      vvp_errors = 0;
+
       draw_execute_header(des);
 
       { int pre = ivl_design_time_precision(des);
@@ -113,6 +116,6 @@ int target_design(ivl_design_t des)
 
       fclose(vvp_out);
 
-      return rc;
+      return rc + vvp_errors;
 }
 
diff --git a/tgt-vvp/vvp_priv.h b/tgt-vvp/vvp_priv.h
index f96099961..53c31618e 100644
--- a/tgt-vvp/vvp_priv.h
+++ b/tgt-vvp/vvp_priv.h
@@ -29,6 +29,11 @@
  */
 extern FILE* vvp_out;
 
+/*
+ * Keep a count of errors that would render the output unusable.
+ */
+extern int vvp_errors;
+
 struct vector_info {
       unsigned base;
       unsigned wid;
diff --git a/tgt-vvp/vvp_process.c b/tgt-vvp/vvp_process.c
index 8fa8830dc..572dc48ab 100644
--- a/tgt-vvp/vvp_process.c
+++ b/tgt-vvp/vvp_process.c
@@ -374,6 +374,14 @@ static int show_stmt_assign_vector(ivl_statement_t net)
 	    vec.base = allocate_vector(wid);
 	    vec.wid = wid;
 
+	    if (vec.base == 0) {
+		  fprintf(stderr, "%s:%u: vvp.tgt error: "
+			  "Unable to allocate %u thread bits for "
+			  "r-value expression.\n", ivl_expr_file(rval),
+			  ivl_expr_lineno(rval), wid);
+		  vvp_errors += 1;
+	    }
+
 	    fprintf(vvp_out, "    %%cvt/vr %u, %d, %u;\n",
 		    vec.base, word, vec.wid);
 
@@ -604,6 +612,7 @@ static int show_stmt_block_named(ivl_statement_t net, ivl_scope_t scope)
 
 static int show_stmt_case(ivl_statement_t net, ivl_scope_t sscope)
 {
+      int rc = 0;
       ivl_expr_t exp = ivl_stmt_cond_expr(net);
       struct vector_info cond = draw_eval_expr(exp, 0);
       unsigned count = ivl_stmt_case_count(net);
@@ -688,7 +697,7 @@ static int show_stmt_case(ivl_statement_t net, ivl_scope_t sscope)
 	/* Emit code for the default case. */
       if (default_case < count) {
 	    ivl_statement_t cst = ivl_stmt_case_stmt(net, default_case);
-	    show_statement(cst, sscope);
+	    rc += show_statement(cst, sscope);
       }
 
 	/* Jump to the out of the case. */
@@ -703,7 +712,7 @@ static int show_stmt_case(ivl_statement_t net, ivl_scope_t sscope)
 
 	    fprintf(vvp_out, "T_%d.%d ;\n", thread_count, local_base+idx);
 	    clear_expression_lookaside();
-	    show_statement(cst, sscope);
+	    rc += show_statement(cst, sscope);
 
 	    fprintf(vvp_out, "    %%jmp T_%d.%d;\n", thread_count,
 		    local_base+count);
@@ -715,11 +724,12 @@ static int show_stmt_case(ivl_statement_t net, ivl_scope_t sscope)
       fprintf(vvp_out, "T_%d.%d ;\n",  thread_count, local_base+count);
       clear_expression_lookaside();
 
-      return 0;
+      return rc;
 }
 
 static int show_stmt_case_r(ivl_statement_t net, ivl_scope_t sscope)
 {
+      int rc = 0;
       ivl_expr_t exp = ivl_stmt_cond_expr(net);
       int cond = draw_eval_real(exp);
       unsigned count = ivl_stmt_case_count(net);
@@ -762,7 +772,7 @@ static int show_stmt_case_r(ivl_statement_t net, ivl_scope_t sscope)
 	   fall through to this statement. */
       if (default_case < count) {
 	    ivl_statement_t cst = ivl_stmt_case_stmt(net, default_case);
-	    show_statement(cst, sscope);
+	    rc += show_statement(cst, sscope);
       }
 
 	/* Jump to the out of the case. */
@@ -777,7 +787,7 @@ static int show_stmt_case_r(ivl_statement_t net, ivl_scope_t sscope)
 
 	    fprintf(vvp_out, "T_%d.%d ;\n", thread_count, local_base+idx);
 	    clear_expression_lookaside();
-	    show_statement(cst, sscope);
+	    rc += show_statement(cst, sscope);
 
 	    fprintf(vvp_out, "    %%jmp T_%d.%d;\n", thread_count,
 		    local_base+count);
@@ -1344,6 +1354,7 @@ static struct vector_info reduction_or(struct vector_info cvec)
 	    clr_vector(cvec);
 	    result.base = allocate_vector(1);
 	    result.wid = 1;
+	    assert(result.base);
 	    fprintf(vvp_out, "    %%or/r %u, %u, %u;\n", result.base,
 		    cvec.base, cvec.wid);
 	    break;