Fix ABI compatibility (#1961)

include/fmt/format-inl.h

@@ -261,11 +261,19 @@ const uint64_t basic_data<T>::powers_of_10_64[] = {
     10000000000000000000ULL};
 
 template <typename T>
-const uint32_t basic_data<T>::zero_or_powers_of_10_32[] = {0, 0,
+const uint32_t basic_data<T>::zero_or_powers_of_10_32[] = {0,
                                                            FMT_POWERS_OF_10(1)};
-
 template <typename T>
 const uint64_t basic_data<T>::zero_or_powers_of_10_64[] = {
+    0, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
+    10000000000000000000ULL};
+
+template <typename T>
+const uint32_t basic_data<T>::zero_or_powers_of_10_32_new[] = {
+    0, 0, FMT_POWERS_OF_10(1)};
+
+template <typename T>
+const uint64_t basic_data<T>::zero_or_powers_of_10_64_new[] = {
     0, 0, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
     10000000000000000000ULL};
 

include/fmt/format.h

@@ -866,8 +866,8 @@ template <typename T> struct FMT_EXTERN_TEMPLATE_API divtest_table_entry {
 // Static data is placed in this class template for the header-only config.
 template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
   static const uint64_t powers_of_10_64[];
-  static const uint32_t zero_or_powers_of_10_32[];
-  static const uint64_t zero_or_powers_of_10_64[];
+  static const uint32_t zero_or_powers_of_10_32_new[];
+  static const uint64_t zero_or_powers_of_10_64_new[];
   static const uint64_t grisu_pow10_significands[];
   static const int16_t grisu_pow10_exponents[];
   static const divtest_table_entry<uint32_t> divtest_table_for_pow5_32[];
@@ -891,6 +891,10 @@ template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
   static const char signs[];
   static const char left_padding_shifts[5];
   static const char right_padding_shifts[5];
+
+  // DEPRECATED! These are for ABI compatibility.
+  static const uint32_t zero_or_powers_of_10_32[];
+  static const uint64_t zero_or_powers_of_10_64[];
 };
 
 // Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
@@ -917,7 +921,7 @@ struct data : basic_data<> {};
 inline int count_digits(uint64_t n) {
   // https://github.com/fmtlib/format-benchmark/blob/master/digits10
   auto t = bsr2log10(FMT_BUILTIN_CLZLL(n | 1) ^ 63);
-  return t - (n < data::zero_or_powers_of_10_64[t]);
+  return t - (n < data::zero_or_powers_of_10_64_new[t]);
 }
 #else
 // Fallback version of count_digits used when __builtin_clz is not available.
@@ -984,7 +988,7 @@ template <> int count_digits<4>(detail::fallback_uintptr n);
 // Optional version of count_digits for better performance on 32-bit platforms.
 inline int count_digits(uint32_t n) {
   auto t = bsr2log10(FMT_BUILTIN_CLZ(n | 1) ^ 31);
-  return t - (n < data::zero_or_powers_of_10_32[t]);
+  return t - (n < data::zero_or_powers_of_10_32_new[t]);
 }
 #endif
 
@@ -3785,6 +3789,7 @@ extern template void detail::vformat_to(detail::buffer<char>&, string_view,
                                         basic_format_args<format_context>,
                                         detail::locale_ref);
 namespace detail {
+
 extern template FMT_API std::string grouping_impl<char>(locale_ref loc);
 extern template FMT_API std::string grouping_impl<wchar_t>(locale_ref loc);
 extern template FMT_API char thousands_sep_impl<char>(locale_ref loc);

src/format.cc

@@ -28,6 +28,31 @@ template dragonbox::decimal_fp<float> dragonbox::to_decimal(float x)
     FMT_NOEXCEPT;
 template dragonbox::decimal_fp<double> dragonbox::to_decimal(double x)
     FMT_NOEXCEPT;
+
+// DEPRECATED! This function exists for ABI compatibility.
+template <typename Char>
+typename basic_format_context<std::back_insert_iterator<buffer<Char>>,
+                              Char>::iterator
+vformat_to(buffer<Char>& buf, basic_string_view<Char> format_str,
+           basic_format_args<basic_format_context<
+               std::back_insert_iterator<buffer<type_identity_t<Char>>>,
+               type_identity_t<Char>>>
+               args) {
+  using iterator = std::back_insert_iterator<buffer<char>>;
+  using context = basic_format_context<
+      std::back_insert_iterator<buffer<type_identity_t<Char>>>,
+      type_identity_t<Char>>;
+  auto out = iterator(buf);
+  format_handler<iterator, Char, context> h(out, format_str, args, {});
+  parse_format_string<false>(format_str, h);
+  return out;
+}
+template basic_format_context<std::back_insert_iterator<buffer<char>>,
+                              char>::iterator
+vformat_to(buffer<char>&, string_view,
+           basic_format_args<basic_format_context<
+               std::back_insert_iterator<buffer<type_identity_t<char>>>,
+               type_identity_t<char>>>);
 }  // namespace detail
 
 template struct FMT_INSTANTIATION_DEF_API detail::basic_data<void>;