From b7d4f96d195323cf9344a2af6720dfae3d9f299d Mon Sep 17 00:00:00 2001
From: Andy Russell <arussell123@gmail.com>
Date: Thu, 21 Feb 2019 20:21:50 -0500
Subject: [PATCH] rust-lldb: fix crash when printing empty string

---
 src/etc/lldb_rust_formatters.py    |  2 ++
 src/test/debuginfo/empty-string.rs | 33 ++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 src/test/debuginfo/empty-string.rs

diff --git a/src/etc/lldb_rust_formatters.py b/src/etc/lldb_rust_formatters.py
index 2c651c90f82eb..fdc1c4fa0cc38 100644
--- a/src/etc/lldb_rust_formatters.py
+++ b/src/etc/lldb_rust_formatters.py
@@ -290,6 +290,8 @@ def render_element(i):
 
 
 def read_utf8_string(ptr_val, byte_count):
+    if byte_count == 0:
+        return '""'
     error = lldb.SBError()
     process = ptr_val.get_wrapped_value().GetProcess()
     data = process.ReadMemory(ptr_val.as_integer(), byte_count, error)
diff --git a/src/test/debuginfo/empty-string.rs b/src/test/debuginfo/empty-string.rs
new file mode 100644
index 0000000000000..43ce21908a958
--- /dev/null
+++ b/src/test/debuginfo/empty-string.rs
@@ -0,0 +1,33 @@
+// compile-flags:-g
+// min-gdb-version: 7.7
+// min-lldb-version: 310
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command: run
+
+// gdb-command: print empty_string
+// gdb-check:$1 = ""
+
+// gdb-command: print empty_str
+// gdb-check:$2 = ""
+
+// === LLDB TESTS ==================================================================================
+
+// lldb-command: run
+
+// lldb-command: fr v empty_string
+// lldb-check:[...]empty_string = ""
+
+// lldb-command: fr v empty_str
+// lldb-check:[...]empty_str = ""
+
+fn main() {
+    let empty_string = String::new();
+
+    let empty_str = "";
+
+    zzz(); // #break
+}
+
+fn zzz() {}