Add std.dbg.trap(str msg) for help debugging.

src/lib/dbg.rs

@@ -18,6 +18,7 @@ native "rust" mod rustrt {
     fn debug_obj[T](&T x, uint nmethods, uint nbytes);
     fn debug_fn[T](&T x);
     fn debug_ptrcast[T, U](@T x) -> @U;
+    fn debug_trap(str msg);
 }
 
 fn debug_vec[T](vec[T] v) {
@@ -61,6 +62,10 @@ fn ptr_cast[T, U](@T x) -> @U {
     ret rustrt.debug_ptrcast[T, U](x);
 }
 
+fn trap(str s) {
+    rustrt.debug_trap(s);
+}
+
 // Local Variables:
 // mode: rust;
 // fill-column: 78;

src/rt/rust_builtin.cpp

@@ -363,6 +363,14 @@ debug_ptrcast(rust_task *task,
     return ptr;
 }
 
+extern "C" CDECL void
+debug_trap(rust_task *task, rust_str *s)
+{
+    task->log(rust_log::STDLIB, "trapping: %s", s->data);
+    // FIXME: x86-ism.
+    __asm__("int3");
+}
+
 
 //
 // Local Variables: