fix InstructionTextSink panicking in write_char

3 files changed, 36 insertions, 1 deletions

diff --git a/CHANGELOG b/CHANGELOG
index b5ac7b8..d8fd706 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -13,6 +13,10 @@ TODO: impls of `fn one` and `fn zero` so downstream users don't have to import n
 TODO: 0.4.0 or later:
   * remove `mod colors`, crossterm dependency, related feature flags
 
+## 0.3.1
+
+fix InstructionTextSink::write_char to not panic in debug builds
+
 ## 0.3.0
 
 added a new crate feature flag, `alloc`.
diff --git a/src/display/display_sink.rs b/src/display/display_sink.rs
index f5ec026..e83f084 100644
--- a/src/display/display_sink.rs
+++ b/src/display/display_sink.rs
@@ -453,7 +453,9 @@ mod instruction_text_sink {
                 // write single ASCII characters. this is wrong in the general case, but `write_char`
                 // here is not going to be used in the general case.
                 if cfg!(debug_assertions) {
-                    panic!("InstructionTextSink::write_char would truncate output");
+                    if c > '\x7f' {
+                        panic!("InstructionTextSink::write_char would truncate output");
+                    }
                 }
                 let to_push = c as u8;
                 // `ptr::write` here because `underlying.add(underlying.len())` may not point to an
diff --git a/tests/display.rs b/tests/display.rs
index a6d6eb1..8826303 100644
--- a/tests/display.rs
+++ b/tests/display.rs
@@ -19,6 +19,35 @@ fn formatters_are_not_feature_gated() {
 
 #[cfg(feature="alloc")]
 #[test]
+fn instruction_text_sink_write_char_requires_ascii() {
+    use core::fmt::Write;
+
+    let mut text = String::with_capacity(512);
+    let mut sink = unsafe {
+        yaxpeax_arch::display::InstructionTextSink::new(&mut text)
+    };
+    let expected = "`1234567890-=+_)(*&^%$#@!~\\][poiuytrewq	|}{POIUYTREWQ';lkjhgfdsa\":LKJHGFDSA/.,mnbvcxz?><MNBVCXZ \r\n";
+    for c in expected.as_bytes().iter() {
+        sink.write_char(*c as char).expect("write works");
+    }
+    assert_eq!(text, expected);
+}
+
+#[cfg(feature="alloc")]
+#[test]
+#[should_panic]
+fn instruction_text_sink_write_char_rejects_not_ascii() {
+    use core::fmt::Write;
+
+    let mut text = String::with_capacity(512);
+    let mut sink = unsafe {
+        yaxpeax_arch::display::InstructionTextSink::new(&mut text)
+    };
+    sink.write_char('\u{80}').expect("write works");
+}
+
+#[cfg(feature="alloc")]
+#[test]
 fn display_sink_write_hex_helpers() {
     use yaxpeax_arch::display::{DisplaySink};