Remove string_view_metadata

string_view_metadata was introduced to make compiled format relocatable.
However, format string compilation is an optimization and therefore
adding overhead and extra complexity for relocation is undesirable.
In most cases the string will be either static or outlive compilation
and formatting and if it doesn't, it's possible to make compiled
representation relocatale by other means.

include/fmt/chrono.h

@@ -738,8 +738,7 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
 
     FMT_CONSTEXPR arg_ref_type make_arg_ref(basic_string_view<Char> arg_id) {
       context.check_arg_id(arg_id);
-      const auto str_val = internal::string_view_metadata(format_str, arg_id);
-      return arg_ref_type(str_val);
+      return arg_ref_type(arg_id);
     }
 
     FMT_CONSTEXPR arg_ref_type make_arg_ref(internal::auto_id) {

include/fmt/compile.h

@@ -27,11 +27,11 @@ template <typename Char> struct format_part {
   kind part_kind;
   union value {
     unsigned arg_index;
-    string_view_metadata str;
+    basic_string_view<Char> str;
     replacement repl;
 
     FMT_CONSTEXPR value(unsigned index = 0) : arg_index(index) {}
-    FMT_CONSTEXPR value(string_view_metadata s) : str(s) {}
+    FMT_CONSTEXPR value(basic_string_view<Char> s) : str(s) {}
     FMT_CONSTEXPR value(replacement r) : repl(r) {}
   } val;
   std::size_t arg_id_end = 0;  // Position past the end of the argument id.
@@ -42,10 +42,10 @@ template <typename Char> struct format_part {
   static FMT_CONSTEXPR format_part make_arg_index(unsigned index) {
     return format_part(kind::arg_index, index);
   }
-  static FMT_CONSTEXPR format_part make_arg_name(string_view_metadata name) {
+  static FMT_CONSTEXPR format_part make_arg_name(basic_string_view<Char> name) {
     return format_part(kind::arg_name, name);
   }
-  static FMT_CONSTEXPR format_part make_text(string_view_metadata text) {
+  static FMT_CONSTEXPR format_part make_text(basic_string_view<Char> text) {
     return format_part(kind::text, text);
   }
   static FMT_CONSTEXPR format_part make_replacement(replacement repl) {
@@ -105,10 +105,8 @@ class format_string_compiler : public error_handler {
         parse_context_(format_str) {}
 
   FMT_CONSTEXPR void on_text(const Char* begin, const Char* end) {
-    if (begin == end) return;
-    const auto offset = begin - format_str_.data();
-    const auto size = end - begin;
-    handler_(part::make_text(string_view_metadata(offset, size)));
+    if (begin != end)
+      handler_(part::make_text({begin, to_unsigned(end - begin)}));
   }
 
   FMT_CONSTEXPR void on_arg_id() {
@@ -121,7 +119,7 @@ class format_string_compiler : public error_handler {
   }
 
   FMT_CONSTEXPR void on_arg_id(basic_string_view<Char> id) {
-    part_ = part::make_arg_name(string_view_metadata(format_str_, id));
+    part_ = part::make_arg_name(id);
   }
 
   FMT_CONSTEXPR void on_replacement_field(const Char* ptr) {
@@ -191,7 +189,7 @@ class compiled_format {
 
       switch (part.part_kind) {
       case format_part_t::kind::text: {
-        const auto text = value.str.to_view(format_view.data());
+        const auto text = value.str;
         auto output = ctx.out();
         auto&& it = internal::reserve(output, text.size());
         it = std::copy_n(text.begin(), text.size(), it);
@@ -205,15 +203,14 @@ class compiled_format {
 
       case format_part_t::kind::arg_name: {
         advance_parse_context_to_specification(parse_ctx, part);
-        const auto named_arg_id = value.str.to_view(format_view.data());
+        const auto named_arg_id = value.str;
         format_arg<Range>(parse_ctx, ctx, named_arg_id);
       } break;
       case format_part_t::kind::replacement: {
         const auto& arg_id_value = value.repl.arg_id.val;
         const auto arg = value.repl.arg_id.kind == arg_id_kind::index
                              ? ctx.arg(arg_id_value.index)
-                             : ctx.arg(arg_id_value.name.to_view(
-                                   to_string_view(format_).data()));
+                             : ctx.arg(arg_id_value.name);
 
         auto specs = value.repl.specs;
 

include/fmt/format.h

@@ -2114,24 +2114,6 @@ class specs_handler : public specs_setter<typename Context::char_type> {
   Context& context_;
 };
 
-struct string_view_metadata {
-  FMT_CONSTEXPR string_view_metadata() : offset_(0u), size_(0u) {}
-  template <typename Char>
-  FMT_CONSTEXPR string_view_metadata(basic_string_view<Char> primary_string,
-                                     basic_string_view<Char> view)
-      : offset_(to_unsigned(view.data() - primary_string.data())),
-        size_(view.size()) {}
-  FMT_CONSTEXPR string_view_metadata(std::size_t offset, std::size_t size)
-      : offset_(offset), size_(size) {}
-  template <typename Char>
-  FMT_CONSTEXPR basic_string_view<Char> to_view(const Char* str) const {
-    return {str + offset_, size_};
-  }
-
-  std::size_t offset_;
-  std::size_t size_;
-};
-
 enum class arg_id_kind { none, index, name };
 
 // An argument reference.
@@ -2139,7 +2121,7 @@ template <typename Char> struct arg_ref {
   FMT_CONSTEXPR arg_ref() : kind(arg_id_kind::none), val() {}
   FMT_CONSTEXPR explicit arg_ref(int index)
       : kind(arg_id_kind::index), val(index) {}
-  FMT_CONSTEXPR explicit arg_ref(string_view_metadata name)
+  FMT_CONSTEXPR explicit arg_ref(basic_string_view<Char> name)
       : kind(arg_id_kind::name), val(name) {}
 
   FMT_CONSTEXPR arg_ref& operator=(int idx) {
@@ -2152,10 +2134,10 @@ template <typename Char> struct arg_ref {
   union value {
     FMT_CONSTEXPR value() : index(0u) {}
     FMT_CONSTEXPR value(int id) : index(id) {}
-    FMT_CONSTEXPR value(string_view_metadata n) : name(n) {}
+    FMT_CONSTEXPR value(basic_string_view<Char> n) : name(n) {}
 
     int index;
-    string_view_metadata name;
+    basic_string_view<Char> name;
   } val;
 };
 
@@ -2213,8 +2195,7 @@ class dynamic_specs_handler
     context_.check_arg_id(arg_id);
     basic_string_view<char_type> format_str(
         context_.begin(), to_unsigned(context_.end() - context_.begin()));
-    const auto id_metadata = string_view_metadata(format_str, arg_id);
-    return arg_ref_type(id_metadata);
+    return arg_ref_type(arg_id);
   }
 
   dynamic_format_specs<char_type>& specs_;
@@ -2585,7 +2566,7 @@ void handle_dynamic_spec(Spec& value, arg_ref<typename Context::char_type> ref,
                                         ctx.error_handler());
     break;
   case arg_id_kind::name: {
-    const auto arg_id = ref.val.name.to_view(format_str);
+    const auto arg_id = ref.val.name;
     internal::set_dynamic_spec<Handler>(value, ctx.arg(arg_id),
                                         ctx.error_handler());
     break;