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author | Mazdak Farrokhzad <twingoow@gmail.com> | 2019-02-27 13:32:19 +0100 |
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committer | GitHub <noreply@github.com> | 2019-02-27 13:32:19 +0100 |
commit | a46b00eeb5cb78288f04df0ab68b4192c92608c9 (patch) | |
tree | 40c3ea6f481db7065b962c40dfe5780493415876 | |
parent | f6673a4e7ccfd5f5c8de07e24735b1e730aaffb2 (diff) | |
parent | eddd07cc8a92dd603e9884789fb58b2d3edd2e16 (diff) | |
download | rust-a46b00eeb5cb78288f04df0ab68b4192c92608c9.tar.gz |
Rollup merge of #58630 - nnethercote:fix-fold_clobber, r=petrochenkov
Make `visit_clobber` panic-safe.
Local measurements indicate the performance effect is negligible.
r? @petrochenkov
-rw-r--r-- | src/libsyntax/mut_visit.rs | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs index 86849f580d0..bcb96f5786b 100644 --- a/src/libsyntax/mut_visit.rs +++ b/src/libsyntax/mut_visit.rs @@ -21,6 +21,7 @@ use syntax_pos::Span; use rustc_data_structures::sync::Lrc; use std::ops::DerefMut; +use std::{panic, process, ptr}; pub trait ExpectOne<A: Array> { fn expect_one(self, err: &'static str) -> A::Item; @@ -305,11 +306,18 @@ pub trait MutVisitor: Sized { /// Use a map-style function (`FnOnce(T) -> T`) to overwrite a `&mut T`. Useful /// when using a `flat_map_*` or `filter_map_*` method within a `visit_` -/// method. +/// method. Abort the program if the closure panics. // // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`. pub fn visit_clobber<T, F>(t: &mut T, f: F) where F: FnOnce(T) -> T { - unsafe { std::ptr::write(t, f(std::ptr::read(t))); } + unsafe { + // Safe because `t` is used in a read-only fashion by `read()` before + // being overwritten by `write()`. + let old_t = ptr::read(t); + let new_t = panic::catch_unwind(panic::AssertUnwindSafe(|| f(old_t))) + .unwrap_or_else(|_| process::abort()); + ptr::write(t, new_t); + } } // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`. |