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test that we preserve boxes in patterns---still one bug

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This commit is contained in:
Niko Matsakis 2012-05-17 20:18:20 -07:00
parent 3f283bb168
commit a559329692
7 changed files with 255 additions and 61 deletions
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178
src/rustc/middle/borrowck.rs
View File

@ -85,6 +85,7 @@ enum categorization {
cat_stack_upvar(cmt), // upvar in stack closure
cat_deref(cmt, uint, ptr_kind), // deref of a ptr
cat_comp(cmt, comp_kind), // adjust to locate an internal component
cat_discr(cmt, ast::node_id), // alt discriminant (see preserve())
}
// different kinds of pointers:
@ -205,7 +206,8 @@ fn req_loans_in_expr(ex: @ast::expr,
// If this expression is borrowed, have to ensure it remains valid:
for tcx.borrowings.find(ex.id).each { |scope_id|
let cmt = self.bccx.cat_borrow_of_expr(ex);
self.guarantee_valid(cmt, m_const, ty::re_scope(scope_id));
let scope_r = ty::re_scope(scope_id);
self.guarantee_valid(cmt, m_const, scope_r);
}
// Special checks for various kinds of expressions:
@ -224,20 +226,19 @@ fn req_loans_in_expr(ex: @ast::expr,
ast::expr_call(f, args, _) {
let arg_tys = ty::ty_fn_args(ty::expr_ty(self.tcx(), f));
let scope_r = ty::re_scope(ex.id);
vec::iter2(args, arg_tys) { |arg, arg_ty|
alt ty::resolved_mode(self.tcx(), arg_ty.mode) {
ast::by_mutbl_ref {
let arg_cmt = self.bccx.cat_expr(arg);
self.guarantee_valid(arg_cmt, m_mutbl, ty::re_scope(ex.id));
self.guarantee_valid(arg_cmt, m_mutbl, scope_r);
}
ast::by_ref {
let arg_cmt = self.bccx.cat_expr(arg);
if TREAT_CONST_AS_IMM {
self.guarantee_valid(arg_cmt, m_imm,
ty::re_scope(ex.id));
self.guarantee_valid(arg_cmt, m_imm, scope_r);
} else {
self.guarantee_valid(arg_cmt, m_const,
ty::re_scope(ex.id));
self.guarantee_valid(arg_cmt, m_const, scope_r);
}
}
ast::by_move | ast::by_copy | ast::by_val {}
@ -249,7 +250,7 @@ fn req_loans_in_expr(ex: @ast::expr,
let cmt = self.bccx.cat_expr(ex_v);
for arms.each { |arm|
for arm.pats.each { |pat|
self.gather_pat(cmt, pat, arm.body.node.id);
self.gather_pat(cmt, pat, arm.body.node.id, ex.id);
}
}
}
@ -265,8 +266,10 @@ impl methods for gather_loan_ctxt {
fn tcx() -> ty::ctxt { self.bccx.tcx }
// guarantees that addr_of(cmt) will be valid for the duration of
// `scope_r`, or reports an error. This may entail taking out loans,
// which will be added to the `req_loan_map`.
// `static_scope_r`, or reports an error. This may entail taking
// out loans, which will be added to the `req_loan_map`. This can
// also entail "rooting" GC'd pointers, which means ensuring
// dynamically that they are not freed.
fn guarantee_valid(cmt: cmt,
mutbl: ast::mutability,
scope_r: ty::region) {
@ -334,16 +337,24 @@ impl methods for gather_loan_ctxt {
}
}
fn gather_pat(cmt: cmt, pat: @ast::pat, alt_id: ast::node_id) {
fn gather_pat(cmt: cmt, pat: @ast::pat,
arm_id: ast::node_id, alt_id: ast::node_id) {
// Here, `cmt` is the categorization for the value being
// matched and pat is the pattern it is being matched against.
//
// In general, the way that this works is that we
// In general, the way that this works is that we walk down
// the pattern, constructing a cmt that represents the path
// that will be taken to reach the value being matched.
//
// When we encounter named bindings, we take the cmt that has
// been built up and pass it off to guarantee_valid() so that
// we can be sure that the binding will remain valid for the
// duration of the arm.
#debug["gather_pat: id=%d pat=%s cmt=%s alt_id=%d",
#debug["gather_pat: id=%d pat=%s cmt=%s arm_id=%d alt_id=%d",
pat.id, pprust::pat_to_str(pat),
self.bccx.cmt_to_repr(cmt), alt_id];
self.bccx.cmt_to_repr(cmt), arm_id, alt_id];
let _i = indenter();
let tcx = self.tcx();
@ -359,7 +370,7 @@ impl methods for gather_loan_ctxt {
// variant(x, y, z)
for subpats.each { |subpat|
let subcmt = self.bccx.cat_variant(pat, cmt, subpat);
self.gather_pat(subcmt, subpat, alt_id);
self.gather_pat(subcmt, subpat, arm_id, alt_id);
}
}
@ -370,8 +381,16 @@ impl methods for gather_loan_ctxt {
ast::pat_ident(id, o_pat) {
// x or x @ p --- `x` must remain valid for the scope of the alt
#debug["defines identifier %s", pprust::path_to_str(id)];
self.guarantee_valid(cmt, m_const, ty::re_scope(alt_id));
for o_pat.each { |p| self.gather_pat(cmt, p, alt_id); }
// Note: there is a discussion of the function of
// cat_discr in the method preserve():
let cmt1 = self.bccx.cat_discr(cmt, alt_id);
let arm_scope = ty::re_scope(arm_id);
self.guarantee_valid(cmt1, m_const, arm_scope);
for o_pat.each { |p|
self.gather_pat(cmt, p, arm_id, alt_id);
}
}
ast::pat_rec(field_pats, _) {
@ -379,7 +398,7 @@ impl methods for gather_loan_ctxt {
for field_pats.each { |fp|
let cmt_field = self.bccx.cat_field(pat, cmt, fp.ident,
tcx.ty(fp.pat));
self.gather_pat(cmt_field, fp.pat, alt_id);
self.gather_pat(cmt_field, fp.pat, arm_id, alt_id);
}
}
@ -387,15 +406,19 @@ impl methods for gather_loan_ctxt {
// (p1, ..., pN)
for subpats.each { |subpat|
let subcmt = self.bccx.cat_tuple_elt(pat, cmt, subpat);
self.gather_pat(subcmt, subpat, alt_id);
self.gather_pat(subcmt, subpat, arm_id, alt_id);
}
}
ast::pat_box(subpat) | ast::pat_uniq(subpat) {
// @p1, ~p1
alt self.bccx.cat_deref(pat, cmt, 0u, true) {
some(subcmt) { self.gather_pat(subcmt, subpat, alt_id); }
none { tcx.sess.span_bug(pat.span, "Non derefable type"); }
some(subcmt) {
self.gather_pat(subcmt, subpat, arm_id, alt_id);
}
none {
tcx.sess.span_bug(pat.span, "Non derefable type");
}
}
}
@ -1006,6 +1029,10 @@ impl categorize_methods for borrowck_ctxt {
}
}
fn cat_discr(cmt: cmt, alt_id: ast::node_id) -> cmt {
ret @{cat:cat_discr(cmt, alt_id) with *cmt};
}
fn cat_field<N:ast_node>(node: N, base_cmt: cmt,
f_name: str, f_ty: ty::t) -> cmt {
let f_mutbl = alt field_mutbl(self.tcx, base_cmt.ty, f_name) {
@ -1239,6 +1266,7 @@ impl categorize_methods for borrowck_ctxt {
cat_comp(cmt, comp) {
#fmt["%s.%s", self.cat_to_repr(cmt.cat), self.comp_to_repr(comp)]
}
cat_discr(cmt, _) { self.cat_to_repr(cmt.cat) }
}
}
@ -1326,6 +1354,9 @@ impl categorize_methods for borrowck_ctxt {
_ { mut_str + " indexed content" }
}
}
cat_discr(cmt, _) {
self.cmt_to_str(cmt)
}
}
}
@ -1420,20 +1451,9 @@ fn field_mutbl(tcx: ty::ctxt,
// Preserve(Ex, S) holds if ToAddr(Ex) will remain valid for the entirety of
// the scope S.
enum preserve_ctxt = @{
bccx: borrowck_ctxt, opt_scope_id: option<ast::node_id>
};
impl preserve_methods for borrowck_ctxt {
fn preserve(cmt: cmt,
opt_scope_id: option<ast::node_id>) -> bckres<()> {
preserve_ctxt(@{bccx:self, opt_scope_id:opt_scope_id}).preserve(cmt)
}
}
impl preserve_methods for preserve_ctxt {
fn preserve(cmt: cmt) -> bckres<()> {
#debug["preserve(%s)", self.bccx.cmt_to_repr(cmt)];
fn preserve(cmt: cmt, opt_scope_id: option<ast::node_id>) -> bckres<()> {
#debug["preserve(%s)", self.cmt_to_repr(cmt)];
let _i = indenter();
alt cmt.cat {
@ -1441,13 +1461,13 @@ impl preserve_methods for preserve_ctxt {
ok(())
}
cat_stack_upvar(cmt) {
self.preserve(cmt)
self.preserve(cmt, opt_scope_id)
}
cat_local(_) {
// This should never happen. Local variables are always lendable,
// so either `loan()` should be called or there must be some
// intermediate @ or &---they are not lendable but do not recurse.
self.bccx.tcx.sess.span_bug(
self.tcx.sess.span_bug(
cmt.span,
"preserve() called with local");
}
@ -1463,13 +1483,13 @@ impl preserve_methods for preserve_ctxt {
cat_comp(cmt_base, comp_res) {
// Most embedded components: if the base is stable, the
// type never changes.
self.preserve(cmt_base)
self.preserve(cmt_base, opt_scope_id)
}
cat_comp(cmt1, comp_variant) {
self.require_imm(cmt, cmt1, err_mut_variant)
self.require_imm(cmt, cmt1, opt_scope_id, err_mut_variant)
}
cat_deref(cmt1, _, uniq_ptr) {
self.require_imm(cmt, cmt1, err_mut_uniq)
self.require_imm(cmt, cmt1, opt_scope_id, err_mut_uniq)
}
cat_deref(_, _, region_ptr) {
// References are always "stable" by induction (when the
@ -1482,17 +1502,18 @@ impl preserve_methods for preserve_ctxt {
ok(())
}
cat_deref(base, derefs, gc_ptr) {
// GC'd pointers of type @MT: always stable because we can inc
// the ref count or keep a GC root as necessary. We need to
// insert this id into the root_map, however.
alt self.opt_scope_id {
// GC'd pointers of type @MT: always stable because we can
// inc the ref count or keep a GC root as necessary. We
// need to insert this id into the root_map, however.
alt opt_scope_id {
some(scope_id) {
#debug["Inserting root map entry for %s: \
node %d:%u -> scope %d",
self.bccx.cmt_to_repr(cmt), base.id,
self.cmt_to_repr(cmt), base.id,
derefs, scope_id];
let rk = {id: base.id, derefs: derefs};
self.bccx.root_map.insert(rk, scope_id);
self.root_map.insert(rk, scope_id);
ok(())
}
none {
@ -1500,15 +1521,77 @@ impl preserve_methods for preserve_ctxt {
}
}
}
cat_discr(base, alt_id) {
// Subtle: in an alt, we must ensure that each binding
// variable remains valid for the duration of the arm in
// which it appears, presuming that this arm is taken.
// But it is inconvenient in trans to root something just
// for one arm. Therefore, we insert a cat_discr(),
// basically a special kind of category that says "if this
// value must be dynamically rooted, root it for the scope
// `alt_id`.
//
// As an example, consider this scenario:
//
// let mut x = @some(3);
// alt *x { some(y) {...} none {...} }
//
// Technically, the value `x` need only be rooted
// in the `some` arm. However, we evaluate `x` in trans
// before we know what arm will be taken, so we just
// always root it for the duration of the alt.
//
// As a second example, consider *this* scenario:
//
// let x = @mut @some(3);
// alt x { @@some(y) {...} @@none {...} }
//
// Here again, `x` need only be rooted in the `some` arm.
// In this case, the value which needs to be rooted is
// found only when checking which pattern matches: but
// this check is done before entering the arm. Therefore,
// even in this case we just choose to keep the value
// rooted for the entire alt. This means the value will be
// rooted even if the none arm is taken. Oh well.
//
// At first, I tried to optimize the second case to only
// root in one arm, but the result was suboptimal: first,
// it interfered with the construction of phi nodes in the
// arm, as we were adding code to root values before the
// phi nodes were added. This could have been addressed
// with a second basic block. However, the naive approach
// also yielded suboptimal results for patterns like:
//
// let x = @mut @...;
// alt x { @@some_variant(y) | @@some_other_variant(y) {...} }
//
// The reason is that we would root the value once for
// each pattern and not once per arm. This is also easily
// fixed, but it's yet more code for what is really quite
// the corner case.
//
// Nonetheless, if you decide to optimize this case in the
// future, you need only adjust where the cat_discr()
// node appears to draw the line between what will be rooted
// in the *arm* vs the *alt*.
// current scope must be the arm, which is always a child of alt:
assert self.tcx.region_map.get(opt_scope_id.get()) == alt_id;
self.preserve(base, some(alt_id))
}
}
}
fn require_imm(cmt: cmt, cmt1: cmt, code: bckerr_code) -> bckres<()> {
fn require_imm(cmt: cmt,
cmt1: cmt,
opt_scope_id: option<ast::node_id>,
code: bckerr_code) -> bckres<()> {
// Variant contents and unique pointers: must be immutably
// rooted to a preserved address.
alt cmt1.mutbl {
m_mutbl | m_const { err({cmt:cmt, code:code}) }
m_imm { self.preserve(cmt1) }
m_imm { self.preserve(cmt1, opt_scope_id) }
}
}
}
@ -1569,6 +1652,9 @@ impl loan_methods for loan_ctxt {
cat_local(_) | cat_arg(_) | cat_stack_upvar(_) {
self.ok_with_loan_of(cmt, req_mutbl)
}
cat_discr(base, _) {
self.loan(base, req_mutbl)
}
cat_comp(cmt_base, comp_field(_)) |
cat_comp(cmt_base, comp_index(_)) |
cat_comp(cmt_base, comp_tuple) |

31
src/rustc/middle/trans/alt.rs
View File

@ -87,7 +87,7 @@ fn assoc(key: str, list: bind_map) -> option<ValueRef> {
type match_branch =
@{pats: [@ast::pat],
bound: bind_map,
data: @{body: BasicBlockRef,
data: @{bodycx: block,
guard: option<@ast::expr>,
id_map: pat_id_map}};
type match = [match_branch];
@ -302,6 +302,26 @@ fn collect_record_fields(m: match, col: uint) -> [ast::ident] {
ret fields;
}
fn root_pats_as_necessary(bcx: block, m: match, col: uint, val: ValueRef) {
for vec::each(m) {|br|
let pat_id = br.pats[col].id;
alt bcx.ccx().maps.root_map.find({id:pat_id, derefs:0u}) {
none {}
some(scope_id) {
// Note: the scope_id will always be the id of the alt. See the
// extended comment in rustc::middle::borrowck::preserve() for
// details (look for the case covering cat_discr).
let ty = node_id_type(bcx, pat_id);
let val = load_if_immediate(bcx, val, ty);
root_value(bcx, val, ty, scope_id);
ret; // if we kept going, we'd only be rooting same value again
}
}
}
}
fn any_box_pat(m: match, col: uint) -> bool {
for vec::each(m) {|br|
alt br.pats[col].node { ast::pat_box(_) { ret true; } _ { } }
@ -383,9 +403,10 @@ fn compile_submatch(bcx: block, m: match, vals: [ValueRef],
_ { }
}
if !bcx.unreachable {
exits += [{bound: m[0].bound, from: bcx.llbb, to: data.body}];
exits += [{bound: m[0].bound, from: bcx.llbb,
to: data.bodycx.llbb}];
}
Br(bcx, data.body);
Br(bcx, data.bodycx.llbb);
ret;
}
@ -405,6 +426,8 @@ fn compile_submatch(bcx: block, m: match, vals: [ValueRef],
if pat_id == 0 { pat_id = br.pats[col].id; }
}
root_pats_as_necessary(bcx, m, col, val);
let rec_fields = collect_record_fields(m, col);
// Separate path for extracting and binding record fields
if rec_fields.len() > 0u {
@ -639,7 +662,7 @@ fn trans_alt_inner(scope_cx: block, expr: @ast::expr, arms: [ast::arm],
for vec::each(a.pats) {|p|
match += [@{pats: [p],
bound: [],
data: @{body: body.llbb, guard: a.guard,
data: @{bodycx: body, guard: a.guard,
id_map: id_map}}];
}
}

26
src/rustc/middle/trans/base.rs
View File

@ -1681,6 +1681,17 @@ fn trans_assign_op(bcx: block, ex: @ast::expr, op: ast::binop,
save_in(lhs_res.val));
}
fn root_value(bcx: block, val: ValueRef, ty: ty::t,
scope_id: ast::node_id) {
if !bcx.sess().opts.no_asm_comments {
add_comment(bcx, #fmt["preserving until end of scope %d",
scope_id]);
}
let root_loc = alloca(bcx, type_of(bcx.ccx(), ty));
copy_val(bcx, INIT, root_loc, val, ty);
add_root_cleanup(bcx, scope_id, root_loc, ty);
}
fn autoderef(cx: block, e_id: ast::node_id,
v: ValueRef, t: ty::t) -> result_t {
let _icx = cx.insn_ctxt("autoderef");
@ -1693,19 +1704,12 @@ fn autoderef(cx: block, e_id: ast::node_id,
e_id, val_str(ccx.tn, v1), ty_to_str(ccx.tcx, t1),
derefs];
// check if the result of this autoderef must be preserved
// root the autoderef'd value, if necessary:
derefs += 1u;
alt cx.ccx().maps.root_map.find({id:e_id, derefs:derefs}) {
none {}
alt ccx.maps.root_map.find({id:e_id, derefs:derefs}) {
none { }
some(scope_id) {
if !cx.sess().no_asm_comments() {
add_comment(cx, #fmt["preserving until end of scope %d",
scope_id]);
}
let root_loc = alloca(cx, type_of(cx.ccx(), t1));
Store(cx, v1, root_loc);
take_ty(cx, root_loc, t1);
add_root_cleanup(cx, scope_id, root_loc, t1);
root_value(cx, v1, t1, scope_id);
}
}

20
src/test/run-pass/borrowck-preserve-box-in-arm-not-taken.rs Normal file
View File

@ -0,0 +1,20 @@
// xfail-fast (compile-flags unsupported on windows)
// compile-flags:--borrowck=err
// exec-env:RUST_POISON_ON_FREE=1
fn main() {
let x: @mut @option<~int> = @mut @none;
alt x {
@@some(y) {
// here, the refcount of `*x` is bumped so
// `y` remains valid even if `*x` is modified.
*x = @none;
}
@@none {
// here, no bump of the ref count of `*x` is needed, but in
// fact a bump occurs anyway because of how pattern marching
// works.
}
}
}

19
src/test/run-pass/borrowck-preserve-box-in-discr.rs Normal file
View File

@ -0,0 +1,19 @@
// xfail-fast (compile-flags unsupported on windows)
// compile-flags:--borrowck=err
// exec-env:RUST_POISON_ON_FREE=1
fn main() {
let mut x = @{f: ~3};
alt *x {
{f: b_x} {
assert *b_x == 3;
assert ptr::addr_of(*x.f) == ptr::addr_of(*b_x);
x = @{f: ~4};
#debug["ptr::addr_of(*b_x) = %x", ptr::addr_of(*b_x) as uint];
assert *b_x == 3;
assert ptr::addr_of(*x.f) != ptr::addr_of(*b_x);
}
}
}

19
src/test/run-pass/borrowck-preserve-box-in-pat.rs Normal file
View File

@ -0,0 +1,19 @@
// xfail-fast (compile-flags unsupported on windows)
// compile-flags:--borrowck=err
// exec-env:RUST_POISON_ON_FREE=1
fn main() {
let mut x = @mut @{f: ~3};
alt x {
@@{f: b_x} {
assert *b_x == 3;
assert ptr::addr_of(x.f) == ptr::addr_of(b_x);
*x = @{f: ~4};
#debug["ptr::addr_of(*b_x) = %x", ptr::addr_of(*b_x) as uint];
assert *b_x == 3;
assert ptr::addr_of(*x.f) != ptr::addr_of(*b_x);
}
}
}

23
src/test/run-pass/borrowck-preserve-expl-deref.rs Normal file
View File

@ -0,0 +1,23 @@
// xfail-fast (compile-flags unsupported on windows)
// compile-flags:--borrowck=err
// exec-env:RUST_POISON_ON_FREE=1
fn borrow(x: &int, f: fn(x: &int)) {
let before = *x;
f(x);
let after = *x;
assert before == after;
}
fn main() {
let mut x = @{f: ~3};
borrow((*x).f) {|b_x|
assert *b_x == 3;
assert ptr::addr_of(*x.f) == ptr::addr_of(*b_x);
x = @{f: ~4};
#debug["ptr::addr_of(*b_x) = %x", ptr::addr_of(*b_x) as uint];
assert *b_x == 3;
assert ptr::addr_of(*x.f) != ptr::addr_of(*b_x);
}
}