rustc: Stub GC routines

mk/rt.mk

@@ -25,6 +25,7 @@ RUNTIME_CS := rt/sync/timer.cpp \
               rt/rust_kernel.cpp \
               rt/rust_shape.cpp \
               rt/rust_obstack.cpp \
+              rt/rust_gc.cpp \
               rt/memory_region.cpp \
               rt/test/rust_test_harness.cpp \
               rt/test/rust_test_runtime.cpp \

src/rt/rust_gc.cpp

@@ -0,0 +1,70 @@
+// Rust garbage collection.
+
+// TODO: Windows
+#include <utility>
+#include <stdint.h>
+
+#include "rust_internal.h"
+
+#ifdef __WIN32__
+#include <windows.h>
+#else
+#include <dlfcn.h>
+#endif
+
+namespace gc {
+
+struct root {
+    intptr_t frame_offset;
+    uintptr_t dynamic;  // 0 = static, 1 = dynamic
+    type_desc *tydesc;
+};
+
+struct safe_point {
+    uintptr_t n_roots;
+    root roots[0];
+};
+
+class safe_point_map {
+    uintptr_t n_safe_points;
+    const std::pair<void *,const safe_point *> *index;
+    const safe_point *safe_points;
+
+public:
+    safe_point_map() {
+        const uintptr_t *data;
+#ifdef __WIN32__
+        data = (const uintptr_t *)GetProcAddress(GetModuleHandle(NULL),
+                                                 "rust_gc_safe_points");
+#else
+        data = (const uintptr_t *)dlsym(RTLD_DEFAULT, "rust_gc_safe_points");
+#endif
+        n_safe_points = *data++;
+        index = (const std::pair<void *,const safe_point *> *)data;
+        data += n_safe_points;
+        safe_points = (const safe_point *)data;
+    }
+};
+
+void
+gc() {
+    safe_point_map map;
+
+    // TODO
+}
+
+void
+maybe_gc() {
+    // FIXME: We ought to lock this.
+    static int zeal = -1;
+    if (zeal == -1) {
+        char *ev = getenv("RUST_GC_ZEAL");
+        zeal = ev[0] != '\0' && ev[0] != '0';
+    }
+
+    if (zeal)
+        gc();
+}
+
+}
+