From 35e24fc52fb93d3870fc2ca02020c235f50b6faa Mon Sep 17 00:00:00 2001
From: Ariel Ben-Yehuda <arielby@amazon.com>
Date: Thu, 5 Dec 2024 09:00:29 +0000
Subject: [PATCH 1/2] change legacy_demangle to be more idiomatic C

the code used to be translated line-to-line from Rust iterators, change
it to be more idiomatic C and guarantee there is no weird for loop.

Fuzzing passes.
---
 crates/native-c/src/demangle.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/crates/native-c/src/demangle.c b/crates/native-c/src/demangle.c
index bb36fe4..b28baf6 100644
--- a/crates/native-c/src/demangle.c
+++ b/crates/native-c/src/demangle.c
@@ -1707,10 +1707,8 @@ NODISCARD static demangle_status rust_demangle_legacy_demangle(const char *s, si
     if (chars_len == 0) {
         return DemangleInvalid;
     }
-    char c = *chars++;
-    chars_len--;
-
-    while (c != 'E') {
+    char c;
+    while ((c = *chars) != 'E') {
         // Decode an identifier element's length
         if (c < '0' || c > '9') {
             return DemangleInvalid;
@@ -1726,25 +1724,25 @@ NODISCARD static demangle_status rust_demangle_legacy_demangle(const char *s, si
                 return DemangleInvalid;
             }
             len += d;
+
+            chars++;
+            chars_len--;
             if (chars_len == 0) {
                 return DemangleInvalid;
             }
-            c = *chars++;
-            chars_len--;
+            c = *chars;
         }
 
         // Advance by the length
-        for (size_t i = 0; i < len; i++) {
-            if (chars_len == 0) {
-                return DemangleInvalid;
-            }
-            c = *chars++;
-            chars_len--;
+        if (chars_len <= len) {
+            return DemangleInvalid;
         }
+        chars += len;
+        chars_len -= len;
         elements++;
     }
     *res = (struct demangle_legacy) { inner, inner_len, elements };
-    *rest = chars;
+    *rest = chars + 1;
     return DemangleOk;
 }
 

From 80e40f57d99fa0a63f793c02ec7b0b9e0155ad80 Mon Sep 17 00:00:00 2001
From: Ariel Ben-Yehuda <arielby@amazon.com>
Date: Thu, 5 Dec 2024 09:02:31 +0000
Subject: [PATCH 2/2] add comment about finding latest version of code

---
 crates/native-c/src/demangle.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crates/native-c/src/demangle.c b/crates/native-c/src/demangle.c
index b28baf6..e4eb399 100644
--- a/crates/native-c/src/demangle.c
+++ b/crates/native-c/src/demangle.c
@@ -1,6 +1,8 @@
 // Code for demangling Rust symbols. This code is mostly
 // a line-by-line translation of the Rust code in `rustc-demangle`.
 
+// you can find the latest version of this code in https://github.com/rust-lang/rustc-demangle
+
 #include <stdint.h>
 #include <stddef.h>
 #include <string.h>