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Allow moving out of mutable unsafe pointers

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This makes it possible to de-initialize values anywhere in
memory, which is needed, for example, for a fast imlementation
of vec::pop.
This commit is contained in:
Marijn Haverbeke 2012-01-27 17:15:31 +01:00
parent dc55c06aa3
commit 362625008a
2 changed files with 20 additions and 10 deletions
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22
src/comp/middle/mut.rs
View file

@ -5,7 +5,7 @@ import syntax::visit;
import syntax::ast_util;
import driver::session::session;
enum deref_t { unbox, field, index, }
enum deref_t { unbox(bool), field, index, }
type deref = @{mut: bool, kind: deref_t, outer_t: ty::t};
@ -20,15 +20,15 @@ fn expr_root(tcx: ty::ctxt, ex: @expr, autoderef: bool) ->
while true {
alt ty::struct(tcx, t) {
ty::ty_box(mt) {
ds += [@{mut: mt.mut == mut, kind: unbox, outer_t: t}];
ds += [@{mut: mt.mut == mut, kind: unbox(false), outer_t: t}];
t = mt.ty;
}
ty::ty_uniq(mt) {
ds += [@{mut: mt.mut == mut, kind: unbox, outer_t: t}];
ds += [@{mut: mt.mut == mut, kind: unbox(false), outer_t: t}];
t = mt.ty;
}
ty::ty_res(_, inner, tps) {
ds += [@{mut: false, kind: unbox, outer_t: t}];
ds += [@{mut: false, kind: unbox(false), outer_t: t}];
t = ty::substitute_type_params(tcx, tps, inner);
}
ty::ty_enum(did, tps) {
@ -37,7 +37,7 @@ fn expr_root(tcx: ty::ctxt, ex: @expr, autoderef: bool) ->
vec::len(variants[0].args) != 1u {
break;
}
ds += [@{mut: false, kind: unbox, outer_t: t}];
ds += [@{mut: false, kind: unbox(false), outer_t: t}];
t = ty::substitute_type_params(tcx, tps, variants[0].args[0]);
}
_ { break; }
@ -85,15 +85,16 @@ fn expr_root(tcx: ty::ctxt, ex: @expr, autoderef: bool) ->
expr_unary(op, base) {
if op == deref {
let base_t = ty::expr_ty(tcx, base);
let is_mut = false;
let is_mut = false, ptr = false;
alt ty::struct(tcx, base_t) {
ty::ty_box(mt) { is_mut = mt.mut == mut; }
ty::ty_uniq(mt) { is_mut = mt.mut == mut; }
ty::ty_res(_, _, _) { }
ty::ty_enum(_, _) { }
ty::ty_ptr(mt) { is_mut = mt.mut == mut; }
ty::ty_ptr(mt) { is_mut = mt.mut == mut; ptr = true; }
}
ds += [@{mut: is_mut, kind: unbox, outer_t: base_t}];
ds += [@{mut: is_mut, kind: unbox(ptr && is_mut),
outer_t: base_t}];
ex = base;
} else { break; }
}
@ -187,7 +188,7 @@ fn check_lval(cx: @ctx, dest: @expr, msg: msg) {
} else if !root.ds[0].mut {
let name =
alt root.ds[0].kind {
mut::unbox { "immutable box" }
mut::unbox(_) { "immutable box" }
mut::field { "immutable field" }
mut::index { "immutable vec content" }
};
@ -212,7 +213,8 @@ fn check_move_rhs(cx: @ctx, src: @expr) {
let root = expr_root(cx.tcx, src, false);
// Not a path and no-derefs means this is a temporary.
if vec::len(*root.ds) != 0u {
if vec::len(*root.ds) != 0u &&
root.ds[vec::len(*root.ds) - 1u].kind != unbox(true) {
cx.tcx.sess.span_err(src.span, "moving out of a data structure");
}
}

8
src/libcore/vec.rs
View file

@ -307,6 +307,14 @@ fn pop<T: copy>(&v: [const T]) -> T {
let e = v[ln];
v = slice(v, 0u, ln);
ret e;
// FIXME use this implementation after the next snapshot (27.01.2012)
/* let new_ln = len(v) - 1u;
assert (new_ln > 0u);
let valptr = ptr::mut_addr_of(v[new_ln]);
let val <- *valptr;
unsafe::set_len(v, new_ln);
val
*/
}
/*