Implement va block arg without result:

  Process NULL res in va_block_arg_builtin for all targets.
  Process null desirable_dest for va_arg in gen.
  Add new test issue361.c.

c-tests/new/issue361.c

@@ -0,0 +1,17 @@
+#include <stdarg.h>
+struct car {
+  char a;
+  long d;
+};
+
+o (int n, ...) {
+  struct car c0, c;
+  va_list args;
+  va_arg (args, struct car);
+  int n0;
+  c = va_arg (args, struct car);
+  int n2 = (args);
+  return 0;
+}
+
+int main (void) { return 0; }

c2mir/c2mir.c

@@ -12809,14 +12809,20 @@ static op_t gen (c2m_ctx_t c2m_ctx, node_t r, MIR_label_t true_label, MIR_label_
           op2 = mem_to_address (c2m_ctx, op2, FALSE);
       }
       if (type->mode == TM_STRUCT || type->mode == TM_UNION) {
-        assert (desirable_dest != NULL && desirable_dest->mir_op.mode == MIR_OP_MEM);
-        res = mem_to_address (c2m_ctx, *desirable_dest, TRUE);
+        if (desirable_dest == NULL) {
+          res = get_new_temp (c2m_ctx, MIR_T_I64);
+          MIR_append_insn (ctx, curr_func,
+                           MIR_new_insn (ctx, MIR_MOV, res.mir_op, MIR_new_int_op (ctx, 0)));
+        } else {
+          assert (desirable_dest->mir_op.mode == MIR_OP_MEM);
+          res = mem_to_address (c2m_ctx, *desirable_dest, TRUE);
+        }
         MIR_append_insn (ctx, curr_func,
                          MIR_new_insn (ctx, MIR_VA_BLOCK_ARG, res.mir_op, op2.mir_op,
                                        MIR_new_int_op (ctx, type_size (c2m_ctx, type)),
                                        MIR_new_int_op (ctx, target_get_blk_type (c2m_ctx, type)
                                                               - MIR_T_BLK)));
-        res = *desirable_dest;
+        if (desirable_dest != NULL) res = *desirable_dest;
       } else {
         MIR_append_insn (ctx, curr_func,
                          MIR_new_insn (ctx, MIR_VA_ARG, op1.mir_op, op2.mir_op,

mir-aarch64.c

@@ -110,7 +110,7 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase MIR_UNUS
     a = *(void **) a;
     va->arg_area++;
   }
-  memcpy (res, a, s);
+  if (res != NULL) memcpy (res, a, s);
 #else
   void *a;
   long size = (s + 7) / 8 * 8;
@@ -119,7 +119,7 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase MIR_UNUS
     a = va->__stack;
     va->__stack = (char *) va->__stack + size;
     va->__gr_offs += size;
-    memcpy (res, a, s);
+    if (res != NULL) memcpy (res, a, s);
     return;
   }
   if (size > 2 * 8) size = 8;
@@ -131,7 +131,7 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase MIR_UNUS
     va->__stack = (char *) va->__stack + size;
   }
   if (s > 2 * 8) a = *(void **) a; /* address */
-  memcpy (res, a, s);
+  if (res != NULL) memcpy (res, a, s);
 #endif
 }
 

mir-ppc64.c

@@ -201,7 +201,7 @@ void *va_arg_builtin (void *p, uint64_t t) {
 void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase MIR_UNUSED) {
   struct ppc64_va_list *va = p;
   void *a = va->arg_area;
-  memcpy (res, a, s);
+  if (res != NULL) memcpy (res, a, s);
   va->arg_area += (s + sizeof (uint64_t) - 1) / sizeof (uint64_t);
 }
 

mir-riscv64.c

@@ -103,7 +103,7 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase) {
     a = *(void **) a;
     va->arg_area++;
   }
-  memcpy (res, a, s);
+  if (res != NULL) memcpy (res, a, s);
 }
 
 void va_start_interp_builtin (MIR_context_t ctx MIR_UNUSED, void *p, void *a) {

mir-s390x.c

@@ -252,7 +252,8 @@ void *va_arg_builtin (void *p, uint64_t t) {
 }
 
 void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase MIR_UNUSED) {
-  memcpy (res, *(void **) va_arg_builtin (p, MIR_T_I64), s);
+  void *a = *(void **) va_arg_builtin (p, MIR_T_I64);
+  if (res == NULL) memcpy (res, a, s);
 }
 
 void va_start_interp_builtin (MIR_context_t ctx MIR_UNUSED, void *p, void *a) {

mir-x86_64.c

@@ -81,7 +81,7 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase) {
       u[1].i = *(uint64_t *) ((char *) va->reg_save_area + va->gp_offset);
       va->gp_offset += 8;
     }
-    memcpy (res, &u, s);
+    if (res != NULL) memcpy (res, &u, s);
     return;
   case 2:
     u[0].d = *(double *) ((char *) va->reg_save_area + va->fp_offset);
@@ -90,7 +90,7 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase) {
       u[1].d = *(double *) ((char *) va->reg_save_area + va->fp_offset);
       va->fp_offset += 16;
     }
-    memcpy (res, &u, s);
+    if (res != NULL) memcpy (res, &u, s);
     return;
   case 3:
   case 4:
@@ -104,11 +104,11 @@ void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase) {
     }
     va->fp_offset += 8;
     va->gp_offset += 8;
-    memcpy (res, &u, s);
+    if (res != NULL) memcpy (res, &u, s);
     return;
   default: break;
   }
-  memcpy (res, a, s);
+  if (res != NULL) memcpy (res, a, s);
   va->overflow_arg_area += size / 8;
 }
 
@@ -136,7 +136,7 @@ void *va_arg_builtin (void *p, uint64_t t) {
 void va_block_arg_builtin (void *res, void *p, size_t s, uint64_t ncase) {
   struct x86_64_va_list *va = p;
   void *a = s <= 8 ? va->arg_area : *(void **) va->arg_area; /* pass by pointer */
-  memcpy (res, a, s);
+  if (res != NULL) memcpy (res, a, s);
   va->arg_area++;
 }