Put type descriptors in strings created by the runtime. Progress on #2638.

mk/rt.mk

@@ -62,6 +62,7 @@ RUNTIME_CS_$(1) := \
               rt/rust_uv.cpp \
               rt/rust_log.cpp \
               rt/rust_port_selector.cpp \
+              rt/rust_util.cpp \
               rt/circular_buffer.cpp \
               rt/isaac/randport.cpp \
               rt/rust_kernel.cpp \

src/rt/rust_upcall.cpp

@@ -373,9 +373,7 @@ upcall_s_str_new_shared(s_str_new_shared_args *args) {
     size_t str_fill = args->len + 1;
     size_t str_alloc = str_fill;
     args->retval = (rust_opaque_box *)
-        task->kernel->malloc(sizeof(rust_opaque_box) +
-                             vec_size<char>(str_fill),
-                             "str_new_shared");
+        task->boxed.malloc(&str_body_tydesc, str_fill);
     rust_str *str = (rust_str *)box_body(args->retval);
     str->body.fill = str_fill;
     str->body.alloc = str_alloc;
@@ -425,6 +423,7 @@ upcall_s_str_concat(s_str_concat_args *args) {
     rust_vec_box* v = (rust_vec_box*)
         task->kernel->malloc(fill + sizeof(rust_vec_box),
                              "str_concat");
+    v->header.td = args->lhs->header.td;
     v->body.fill = v->body.alloc = fill;
     memmove(&v->body.data[0], &lhs->data[0], lhs->fill - 1);
     memmove(&v->body.data[lhs->fill - 1], &rhs->data[0], rhs->fill);

src/rt/rust_util.cpp

@@ -0,0 +1,43 @@
+#include "rust_type.h"
+#include "rust_shape.h"
+
+
+// A hardcoded type descriptor for strings, since the runtime needs to
+// be able to create them.
+
+struct rust_shape_tables empty_shape_tables;
+
+uint8_t str_body_shape[] = {
+    shape::SHAPE_UNBOXED_VEC,
+    0x1, // is_pod
+    0x1, 0x0, // size field: 1
+    shape::SHAPE_U8
+};
+
+struct type_desc str_body_tydesc = {
+    0, // unused
+    1, // size
+    1, // align
+    NULL, // take_glue
+    NULL, // drop_glue
+    NULL, // free_glue
+    NULL, // visit_glue
+    0, // unused
+    0, // unused
+    0, // unused
+    0, // unused
+    str_body_shape, // shape
+    &empty_shape_tables, // shape_tables
+    0, // unused
+    0, // unused
+};
+
+//
+// Local Variables:
+// mode: C++
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// End:
+//

src/rt/rust_util.h

@@ -5,6 +5,8 @@
 #include "rust_task.h"
 #include "rust_env.h"
 
+extern struct type_desc str_body_tydesc;
+
 // Inline fn used regularly elsewhere.
 
 static inline size_t
@@ -82,6 +84,7 @@ make_str(rust_kernel* kernel, const char* c, size_t strlen,
     size_t str_alloc = str_fill;
     rust_str *str = (rust_str *)
         kernel->malloc(vec_size<char>(str_fill), name);
+    str->header.td = &str_body_tydesc;
     str->body.fill = str_fill;
     str->body.alloc = str_alloc;
     memcpy(&str->body.data, c, strlen);
@@ -94,6 +97,8 @@ make_str_vec(rust_kernel* kernel, size_t nstrs, char **strs) {
     rust_vec_box *v = (rust_vec_box *)
         kernel->malloc(vec_size<rust_vec_box*>(nstrs),
                        "str vec interior");
+    // FIXME: should have a real td (Issue #2639)
+    v->header.td = NULL;
     v->body.fill = v->body.alloc = sizeof(rust_vec_box*) * nstrs;
     for (size_t i = 0; i < nstrs; ++i) {
         rust_str *str = make_str(kernel, strs[i],