From e382265a615e8d038e8dbfa707379a9cb0debd78 Mon Sep 17 00:00:00 2001
From: Evan Haas <evan@lagerdata.com>
Date: Mon, 25 Dec 2023 14:34:34 -0800
Subject: [PATCH] Diagnostics: handle macro backtrace limit of 1

---
 src/aro/Diagnostics.zig            | 2 +-
 test/cases/macro backtrace limit.c | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 test/cases/macro backtrace limit.c

diff --git a/src/aro/Diagnostics.zig b/src/aro/Diagnostics.zig
index f0c08a36..472c4c3c 100644
--- a/src/aro/Diagnostics.zig
+++ b/src/aro/Diagnostics.zig
@@ -291,7 +291,7 @@ pub fn addExtra(
                 .kind = .note,
                 .extra = .{ .unsigned = expansion_locs.len - d.macro_backtrace_limit },
             });
-            i = half - 1;
+            i = half -| 1;
             while (i > 0) {
                 i -= 1;
                 d.list.appendAssumeCapacity(.{
diff --git a/test/cases/macro backtrace limit.c b/test/cases/macro backtrace limit.c
new file mode 100644
index 00000000..e2d15067
--- /dev/null
+++ b/test/cases/macro backtrace limit.c	
@@ -0,0 +1,8 @@
+//aro-args -fmacro-backtrace-limit=1
+#define FOO(X) X
+FOO(2)
+
+#define EXPECTED_ERRORS "macro backtrace limit.c:3:1: error: expected external declaration" \
+    "note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)" \
+    "macro backtrace limit.c:3:5: note: expanded from here" \
+