Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Issue #8625: Assign to &mut in borrowed or aliasable location #8797

Closed
wants to merge 4 commits into from
Closed

Issue #8625: Assign to &mut in borrowed or aliasable location #8797

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
0ea2a20
Add PointerKind to LpDeref
nikomatsakis Aug 20, 2013
6b23d20
Prohibit assignment to `&mut` pointers that are found in frozen or bo…
nikomatsakis Aug 21, 2013
35a4177
Extend aliasability check to uncover `& &mut &mut` and the like
nikomatsakis Aug 27, 2013
8c09865
Remove remnants of implicit self
nikomatsakis Aug 27, 2013
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion src/librustc/middle/astencode.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -383,7 +383,7 @@ impl tr for ast::def {
ast::def_method(did0.tr(xcx), did1.map(|did1| did1.tr(xcx)))
}
ast::def_self_ty(nid) => { ast::def_self_ty(xcx.tr_id(nid)) }
ast::def_self(nid, i) => { ast::def_self(xcx.tr_id(nid), i) }
ast::def_self(nid) => { ast::def_self(xcx.tr_id(nid)) }
ast::def_mod(did) => { ast::def_mod(did.tr(xcx)) }
ast::def_foreign_mod(did) => { ast::def_foreign_mod(did.tr(xcx)) }
ast::def_static(did, m) => { ast::def_static(did.tr(xcx), m) }
Expand Down
71 changes: 58 additions & 13 deletions src/librustc/middle/borrowck/check_loans.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -352,7 +352,6 @@ impl<'self> CheckLoanCtxt<'self> {

mc::cat_rvalue(*) |
mc::cat_static_item |
mc::cat_implicit_self |
mc::cat_copied_upvar(*) |
mc::cat_deref(_, _, mc::unsafe_ptr(*)) |
mc::cat_deref(_, _, mc::gc_ptr(*)) |
Expand Down Expand Up @@ -391,15 +390,7 @@ impl<'self> CheckLoanCtxt<'self> {
mc::cat_deref(b, _, mc::region_ptr(m_mutbl, _)) => {
// Statically prohibit writes to `&mut` when aliasable

match b.freely_aliasable() {
None => {}
Some(cause) => {
this.bccx.report_aliasability_violation(
expr.span,
MutabilityViolation,
cause);
}
}
check_for_aliasability_violation(this, expr, b);
}

mc::cat_deref(_, deref_count, mc::gc_ptr(ast::m_mutbl)) => {
Expand All @@ -419,6 +410,51 @@ impl<'self> CheckLoanCtxt<'self> {
return true; // no errors reported
}

fn check_for_aliasability_violation(this: &CheckLoanCtxt,
expr: @ast::expr,
cmt: mc::cmt) -> bool {
let mut cmt = cmt;

loop {
match cmt.cat {
mc::cat_deref(b, _, mc::region_ptr(m_mutbl, _)) |
mc::cat_downcast(b) |
mc::cat_stack_upvar(b) |
mc::cat_deref(b, _, mc::uniq_ptr) |
mc::cat_interior(b, _) |
mc::cat_discr(b, _) => {
// Aliasability depends on base cmt
cmt = b;
}

mc::cat_copied_upvar(_) |
mc::cat_rvalue(*) |
mc::cat_local(*) |
mc::cat_arg(_) |
mc::cat_self(*) |
mc::cat_deref(_, _, mc::unsafe_ptr(*)) |
mc::cat_static_item(*) |
mc::cat_deref(_, _, mc::gc_ptr(_)) |
mc::cat_deref(_, _, mc::region_ptr(m_const, _)) |
mc::cat_deref(_, _, mc::region_ptr(m_imm, _)) => {
// Aliasability is independent of base cmt
match cmt.freely_aliasable() {
None => {
return true;
}
Some(cause) => {
this.bccx.report_aliasability_violation(
expr.span,
MutabilityViolation,
cause);
return false;
}
}
}
}
}
}

fn check_for_assignment_to_restricted_or_frozen_location(
this: &CheckLoanCtxt,
expr: @ast::expr,
Expand Down Expand Up @@ -496,6 +532,12 @@ impl<'self> CheckLoanCtxt<'self> {
// path, and check that the super path was not lent out as
// mutable or immutable (a const loan is ok).
//
// Mutability of a path can be dependent on the super path
// in two ways. First, it might be inherited mutability.
// Second, the pointee of an `&mut` pointer can only be
// mutated if it is found in an unaliased location, so we
// have to check that the owner location is not borrowed.
//
// Note that we are *not* checking for any and all
// restrictions. We are only interested in the pointers
// that the user created, whereas we add restrictions for
Expand All @@ -513,9 +555,12 @@ impl<'self> CheckLoanCtxt<'self> {
let mut loan_path = loan_path;
loop {
match *loan_path {
// Peel back one layer if `loan_path` has
// inherited mutability
LpExtend(lp_base, mc::McInherited, _) => {
// Peel back one layer if, for `loan_path` to be
// mutable, `lp_base` must be mutable. This occurs
// with inherited mutability and with `&mut`
// pointers.
LpExtend(lp_base, mc::McInherited, _) |
LpExtend(lp_base, _, LpDeref(mc::region_ptr(ast::m_mutbl, _))) => {
loan_path = lp_base;
}

Expand Down
1 change: 0 additions & 1 deletion src/librustc/middle/borrowck/gather_loans/gather_moves.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,6 @@ fn check_is_legal_to_move_from(bccx: @BorrowckCtxt,
cmt0: mc::cmt,
cmt: mc::cmt) -> bool {
match cmt.cat {
mc::cat_implicit_self(*) |
mc::cat_deref(_, _, mc::region_ptr(*)) |
mc::cat_deref(_, _, mc::gc_ptr(*)) |
mc::cat_deref(_, _, mc::unsafe_ptr(*)) => {
Expand Down
3 changes: 0 additions & 3 deletions src/librustc/middle/borrowck/gather_loans/lifetime.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,6 @@ impl GuaranteeLifetimeContext {

match cmt.cat {
mc::cat_rvalue(*) |
mc::cat_implicit_self |
mc::cat_copied_upvar(*) | // L-Local
mc::cat_local(*) | // L-Local
mc::cat_arg(*) | // L-Local
Expand Down Expand Up @@ -301,7 +300,6 @@ impl GuaranteeLifetimeContext {
}
mc::cat_rvalue(*) |
mc::cat_static_item |
mc::cat_implicit_self |
mc::cat_copied_upvar(*) |
mc::cat_deref(*) => {
false
Expand All @@ -328,7 +326,6 @@ impl GuaranteeLifetimeContext {
mc::cat_rvalue(cleanup_scope_id) => {
ty::re_scope(cleanup_scope_id)
}
mc::cat_implicit_self |
mc::cat_copied_upvar(_) => {
ty::re_scope(self.item_scope_id)
}
Expand Down
13 changes: 6 additions & 7 deletions src/librustc/middle/borrowck/gather_loans/restrictions.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -101,7 +101,7 @@ impl RestrictionsContext {
self.extend(result, cmt.mutbl, LpInterior(i), restrictions)
}

mc::cat_deref(cmt_base, _, mc::uniq_ptr) => {
mc::cat_deref(cmt_base, _, pk @ mc::uniq_ptr) => {
// R-Deref-Send-Pointer
//
// When we borrow the interior of an owned pointer, we
Expand All @@ -110,12 +110,11 @@ impl RestrictionsContext {
let result = self.restrict(
cmt_base,
restrictions | RESTR_MUTATE | RESTR_CLAIM);
self.extend(result, cmt.mutbl, LpDeref, restrictions)
self.extend(result, cmt.mutbl, LpDeref(pk), restrictions)
}

mc::cat_copied_upvar(*) | // FIXME(#2152) allow mutation of upvars
mc::cat_static_item(*) |
mc::cat_implicit_self(*) |
mc::cat_deref(_, _, mc::region_ptr(m_imm, _)) |
mc::cat_deref(_, _, mc::gc_ptr(m_imm)) => {
// R-Deref-Imm-Borrowed
Expand All @@ -129,7 +128,7 @@ impl RestrictionsContext {
Safe
}

mc::cat_deref(cmt_base, _, mc::gc_ptr(m_mutbl)) => {
mc::cat_deref(cmt_base, _, pk @ mc::gc_ptr(m_mutbl)) => {
// R-Deref-Managed-Borrowed
//
// Technically, no restrictions are *necessary* here.
Expand Down Expand Up @@ -170,14 +169,14 @@ impl RestrictionsContext {
match opt_loan_path(cmt_base) {
None => Safe,
Some(lp_base) => {
let lp = @LpExtend(lp_base, cmt.mutbl, LpDeref);
let lp = @LpExtend(lp_base, cmt.mutbl, LpDeref(pk));
SafeIf(lp, ~[Restriction {loan_path: lp,
set: restrictions}])
}
}
}

mc::cat_deref(cmt_base, _, mc::region_ptr(m_mutbl, _)) => {
mc::cat_deref(cmt_base, _, pk @ mc::region_ptr(m_mutbl, _)) => {
// Because an `&mut` pointer does not inherit its
// mutability, we can only prevent mutation or prevent
// freezing if it is not aliased. Therefore, in such
Expand All @@ -187,7 +186,7 @@ impl RestrictionsContext {
let result = self.restrict(
cmt_base,
RESTR_ALIAS | RESTR_MUTATE | RESTR_CLAIM);
self.extend(result, cmt.mutbl, LpDeref, restrictions)
self.extend(result, cmt.mutbl, LpDeref(pk), restrictions)
} else {
// R-Deref-Mut-Borrowed-2
Safe
Expand Down
15 changes: 7 additions & 8 deletions src/librustc/middle/borrowck/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -261,7 +261,7 @@ pub enum LoanPath {

#[deriving(Eq, IterBytes)]
pub enum LoanPathElem {
LpDeref, // `*LV` in doc.rs
LpDeref(mc::PointerKind), // `*LV` in doc.rs
LpInterior(mc::InteriorKind) // `LV.f` in doc.rs
}

Expand All @@ -284,8 +284,7 @@ pub fn opt_loan_path(cmt: mc::cmt) -> Option<@LoanPath> {
match cmt.cat {
mc::cat_rvalue(*) |
mc::cat_static_item |
mc::cat_copied_upvar(_) |
mc::cat_implicit_self => {
mc::cat_copied_upvar(_) => {
None
}

Expand All @@ -295,9 +294,9 @@ pub fn opt_loan_path(cmt: mc::cmt) -> Option<@LoanPath> {
Some(@LpVar(id))
}

mc::cat_deref(cmt_base, _, _) => {
mc::cat_deref(cmt_base, _, pk) => {
do opt_loan_path(cmt_base).map_move |lp| {
@LpExtend(lp, cmt.mutbl, LpDeref)
@LpExtend(lp, cmt.mutbl, LpDeref(pk))
}
}

Expand Down Expand Up @@ -728,7 +727,7 @@ impl BorrowckCtxt {
loan_path: &LoanPath,
out: &mut ~str) {
match *loan_path {
LpExtend(_, _, LpDeref) => {
LpExtend(_, _, LpDeref(_)) => {
out.push_char('(');
self.append_loan_path_to_str(loan_path, out);
out.push_char(')');
Expand Down Expand Up @@ -776,7 +775,7 @@ impl BorrowckCtxt {
out.push_str("[]");
}

LpExtend(lp_base, _, LpDeref) => {
LpExtend(lp_base, _, LpDeref(_)) => {
out.push_char('*');
self.append_loan_path_to_str(lp_base, out);
}
Expand Down Expand Up @@ -854,7 +853,7 @@ impl Repr for LoanPath {
fmt!("$(%?)", id)
}

&LpExtend(lp, _, LpDeref) => {
&LpExtend(lp, _, LpDeref(_)) => {
fmt!("%s.*", lp.repr(tcx))
}

Expand Down
Loading