From e98129ec38cd3841489ebcfbf4852c0b584ddc23 Mon Sep 17 00:00:00 2001
From: "David P. Sicilia" <dpsicilia@gmail.com>
Date: Fri, 17 Dec 2021 11:50:25 -0500
Subject: [PATCH] Don't touch begin iterator (pointer) if begin == end.

Fixes #2661.
---
 include/fmt/core.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 9e0e8964575c..a9fa54b8da60 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -2482,6 +2482,8 @@ FMT_CONSTEXPR FMT_INLINE auto parse_format_specs(const Char* begin,
                                                  const Char* end,
                                                  SpecHandler&& handler)
     -> const Char* {
+  if (begin == end) return begin;
+
   if (begin + 1 < end && begin[1] == '}' && is_ascii_letter(*begin) &&
       *begin != 'L') {
     presentation_type type = parse_presentation_type(*begin++);
@@ -2491,8 +2493,6 @@ FMT_CONSTEXPR FMT_INLINE auto parse_format_specs(const Char* begin,
     return begin;
   }
 
-  if (begin == end) return begin;
-
   begin = parse_align(begin, end, handler);
   if (begin == end) return begin;