Do not copy values of type () or _|_

This can trigger a crash because we assume we
can supply null ptrs and undefined values for
values of those types, as we should be treated
them as zero-size.

Interestingly, this crash only shows up (atm)
in non-optimized builds.  Therefore, I added
a -Z no-opt flag so that the new test
(capture_nil) can specify that it should not
run with optimizations enabled.

src/rustc/driver/driver.rs

@@ -514,8 +514,10 @@ fn build_session_options(binary: ~str,
       link::output_type_llvm_assembly | link::output_type_assembly => (),
       _ => debugging_opts |= session::no_asm_comments
     }
-    let opt_level =
+    let opt_level = {
-        if opt_present(matches, ~"O") {
+        if (debugging_opts & session::no_opt) != 0 {
+            No
+        } else if opt_present(matches, ~"O") {
             if opt_present(matches, ~"opt-level") {
                 early_error(demitter, ~"-O and --opt-level both provided");
             }
@@ -531,7 +533,8 @@ fn build_session_options(binary: ~str,
                             ~"to be between 0-3")
               }
             }
-        } else { No };
+        } else { No }
+    };
     let target =
         match target_opt {
             None => host_triple(),

src/rustc/driver/session.rs

@@ -38,25 +38,26 @@ type config =
      uint_type: uint_ty,
      float_type: float_ty};
 
-const ppregions: uint = 1u;
+const ppregions: uint = 1 << 0;
-const time_passes: uint = 2u;
+const time_passes: uint = 1 << 1;
-const count_llvm_insns: uint = 4u;
+const count_llvm_insns: uint = 1 << 2;
-const time_llvm_passes: uint = 8u;
+const time_llvm_passes: uint = 1 << 3;
-const trans_stats: uint = 16u;
+const trans_stats: uint = 1 << 4;
-const no_asm_comments: uint = 32u;
+const no_asm_comments: uint = 1 << 5;
-const no_verify: uint = 64u;
+const no_verify: uint = 1 << 6;
-const trace: uint = 128u;
+const trace: uint = 1 << 7;
 // FIXME (#2377): This exists to transition to a Rust crate runtime
 // It should be removed
-const no_rt: uint = 256u;
+const no_rt: uint = 1 << 8;
-const coherence: uint = 512u;
+const coherence: uint = 1 << 9;
-const borrowck_stats: uint = 1024u;
+const borrowck_stats: uint = 1 << 10;
-const borrowck_note_pure: uint = 2048;
+const borrowck_note_pure: uint = 1 << 11;
-const borrowck_note_loan: uint = 4096;
+const borrowck_note_loan: uint = 1 << 12;
-const no_landing_pads: uint = 8192;
+const no_landing_pads: uint = 1 << 13;
-const debug_llvm: uint = 16384;
+const debug_llvm: uint = 1 << 14;
-const count_type_sizes: uint = 32768;
+const count_type_sizes: uint = 1 << 15;
-const meta_stats: uint = 65536;
+const meta_stats: uint = 1 << 16;
+const no_opt: uint = 1 << 17;
 
 fn debugging_opts_map() -> ~[(~str, ~str, uint)] {
     ~[(~"ppregions", ~"prettyprint regions with \
@@ -82,7 +83,8 @@ fn debugging_opts_map() -> ~[(~str, ~str, uint)] {
      (~"debug-llvm", ~"enable debug output from LLVM", debug_llvm),
      (~"count-type-sizes", ~"count the sizes of aggregate types",
       count_type_sizes),
-     (~"meta-stats", ~"gather metadata statistics", meta_stats)
+     (~"meta-stats", ~"gather metadata statistics", meta_stats),
+     (~"no-opt", ~"do not optimize, even if -O is passed", no_opt),
     ]
 }
 

src/rustc/middle/trans/datum.rs

@@ -241,6 +241,10 @@ impl Datum {
 
         let _icx = bcx.insn_ctxt("copy_to");
 
+        if ty::type_is_nil(self.ty) || ty::type_is_bot(self.ty) {
+            return bcx;
+        }
+
         debug!("copy_to(self=%s, action=%?, dst=%s)",
                self.to_str(bcx.ccx()), action, bcx.val_str(dst));
 

src/test/run-pass/capture_nil.rs

@@ -0,0 +1,29 @@
+// compile-flags:-Z no-opt
+use comm::*;
+
+// This test has to be setup just so to trigger
+// the condition which was causing us a crash.
+// The situation is that we are capturing a
+// () value by ref.  We generally feel free,
+// however, to substitute NULL pointers and
+// undefined values for values of () type, and
+// so this caused a segfault when we copied into
+// the closure.
+//
+// The fix is just to not emit any actual loads
+// or stores for copies of () type (which is of
+// course preferable, as the value itself is
+// irrelevant).
+
+fn foo(&&x: ()) -> Port<()> {
+    let p = Port();
+    let c = Chan(p);
+    do task::spawn() |copy c, copy x| {
+        c.send(x);
+    }
+    p
+}
+
+fn main() {
+    foo(()).recv()
+}