From 502f2b89497fb6ffcfec0786f206f82582cab5e1 Mon Sep 17 00:00:00 2001
From: Giel van Schijndel <giel@mortis.eu>
Date: Fri, 29 Sep 2023 14:50:23 +0200
Subject: [PATCH 1/2] fix: make std::bitset formattable again
It used to be formattable via operator<<(ostream&) implicitly. Make it
formattable again, but this time via formatter specialization.
---
include/fmt/std.h | 26 ++++++++++++++++++++++++++
test/std-test.cc | 8 ++++++++
2 files changed, 34 insertions(+)
diff --git a/include/fmt/std.h b/include/fmt/std.h
index b4e055c28d41..262ad4d209c0 100644
--- a/include/fmt/std.h
+++ b/include/fmt/std.h
@@ -145,6 +145,32 @@ FMT_END_NAMESPACE
#endif
FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <std::size_t N, typename Char>
+struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
+ private:
+ // Functor because C++11 doesn't support generic lambdas.
+ struct writer {
+ const std::bitset<N>& bs;
+
+ template <typename OutputIt>
+ FMT_CONSTEXPR OutputIt operator()(OutputIt out) {
+ for (auto pos = N; pos > 0; --pos) {
+ out = detail::write<Char>(out, bs[pos - 1] ? Char('1') : Char('0'));
+ }
+
+ return out;
+ }
+ };
+
+ public:
+ template <typename FormatContext>
+ auto format(const std::bitset<N>& bs, FormatContext& ctx) const
+ -> decltype(ctx.out()) {
+ return write_padded(ctx, writer{bs});
+ }
+};
+
FMT_EXPORT
template <typename Char>
struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
diff --git a/test/std-test.cc b/test/std-test.cc
index 56904cc9889d..4279fec10b0f 100644
--- a/test/std-test.cc
+++ b/test/std-test.cc
@@ -237,6 +237,14 @@ TEST(std_test, format_const_bit_reference) {
EXPECT_EQ(fmt::format("{} {}", v[0], v[1]), "true false");
}
+TEST(std_test, format_bitset) {
+ const std::bitset<6> bs(42);
+ EXPECT_EQ(fmt::format("{}", bs), "101010");
+ EXPECT_EQ(fmt::format("{:.4}", bs), "101010");
+ EXPECT_EQ(fmt::format("{:0>8}", bs), "00101010");
+ EXPECT_EQ(fmt::format("{:-^12}", bs), "---101010---");
+}
+
TEST(std_test, format_atomic) {
std::atomic<bool> b(false);
EXPECT_EQ(fmt::format("{}", b), "false");
From 40524a3595924bba11af685a87e071b2a524e64b Mon Sep 17 00:00:00 2001
From: Giel van Schijndel <giel@mortis.eu>
Date: Sat, 30 Sep 2023 20:34:42 +0200
Subject: [PATCH 2/2] fix: make nested_formatter constexpr default
constructible
---
include/fmt/format.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 30addcb7f335..433339614ff7 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -4224,6 +4224,8 @@ struct nested_formatter {
formatter<T> formatter_;
public:
+ constexpr nested_formatter() : width_(0), align_(align_t::none) {}
+
FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> const char* {
auto specs = detail::dynamic_format_specs<char>();
auto it = parse_format_specs(