From e01579231d030c52748c261253e8be81ad1feadd Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Thu, 8 Nov 2018 08:48:56 -0800
Subject: [PATCH] Disallow leading zeros in arg-id

---
 include/fmt/format.h | 8 ++++++++
 test/format-test.cc  | 1 +
 2 files changed, 9 insertions(+)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index ccb26454..66d8df5d 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1547,6 +1547,10 @@ FMT_CONSTEXPR bool is_name_start(Char c) {
 template <typename Iterator, typename ErrorHandler>
 FMT_CONSTEXPR unsigned parse_nonnegative_int(Iterator &it, ErrorHandler &&eh) {
   assert('0' <= *it && *it <= '9');
+  if (*it == '0') {
+    ++it;
+    return 0;
+  }
   unsigned value = 0;
   // Convert to unsigned to prevent a warning.
   unsigned max_int = (std::numeric_limits<int>::max)();
@@ -1574,6 +1578,10 @@ template <typename Char, typename ErrorHandler>
 FMT_CONSTEXPR unsigned parse_nonnegative_int(
     const Char *&begin, const Char *end, ErrorHandler &&eh) {
   assert(begin != end && '0' <= *begin && *begin <= '9');
+  if (*begin == '0') {
+    ++begin;
+    return 0;
+  }
   unsigned value = 0;
   // Convert to unsigned to prevent a warning.
   unsigned max_int = (std::numeric_limits<int>::max)();
diff --git a/test/format-test.cc b/test/format-test.cc
index 743e44cd..927eb2a8 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -750,6 +750,7 @@ TEST(FormatterTest, ArgErrors) {
   EXPECT_THROW_MSG(format("{?}"), format_error, "invalid format string");
   EXPECT_THROW_MSG(format("{0"), format_error, "invalid format string");
   EXPECT_THROW_MSG(format("{0}"), format_error, "argument index out of range");
+  EXPECT_THROW_MSG(format("{00}", 42), format_error, "invalid format string");
 
   char format_str[BUFFER_SIZE];
   safe_sprintf(format_str, "{%u", INT_MAX);