Add name splitting

The new DWARF index code works by keeping names pre-split.  That is,
rather than storing a symbol name like "a:🅱️:c", the names "a", "b",
and "c" will be stored separately.

This patch introduces some helper code to split a full name into its
components.

gdb/Makefile.in

@@ -1160,6 +1160,7 @@ COMMON_SFILES = \
 	solib-target.c \
 	source.c \
 	source-cache.c \
+	split-name.c \
 	stabsread.c \
 	stack.c \
 	std-regs.c \
@@ -1448,6 +1449,7 @@ HFILES_NO_SRCDIR = \
 	sparc-ravenscar-thread.h \
 	sparc-tdep.h \
 	sparc64-tdep.h \
+	split-name.h \
 	stabsread.h \
 	stack.h \
 	stap-probe.h \

gdb/split-name.c

@@ -0,0 +1,81 @@
+/* Split a symbol name.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "split-name.h"
+#include "cp-support.h"
+
+/* See split-name.h.  */
+
+std::vector<gdb::string_view>
+split_name (const char *name, split_style style)
+{
+  std::vector<gdb::string_view> result;
+  unsigned int previous_len = 0;
+
+  switch (style)
+    {
+    case split_style::CXX:
+      for (unsigned int current_len = cp_find_first_component (name);
+	   name[current_len] != '\0';
+	   current_len += cp_find_first_component (name + current_len))
+	{
+	  gdb_assert (name[current_len] == ':');
+	  result.emplace_back (&name[previous_len],
+			       current_len - previous_len);
+	  /* Skip the '::'.  */
+	  current_len += 2;
+	  previous_len = current_len;
+	}
+      break;
+
+    case split_style::UNDERSCORE:
+      /* Handle the Ada encoded (aka mangled) form here.  */
+      for (const char *iter = strstr (name, "__");
+	   iter != nullptr;
+	   iter = strstr (iter, "__"))
+	{
+	  result.emplace_back (&name[previous_len],
+			       iter - &name[previous_len]);
+	  iter += 2;
+	  previous_len = iter - name;
+	}
+      break;
+
+    case split_style::DOT:
+      /* D and Go-style names.  */
+      for (const char *iter = strchr (name, '.');
+	   iter != nullptr;
+	   iter = strchr (iter, '.'))
+	{
+	  result.emplace_back (&name[previous_len],
+			       iter - &name[previous_len]);
+	  ++iter;
+	  previous_len = iter - name;
+	}
+      break;
+
+    default:
+      break;
+    }
+
+  result.emplace_back (&name[previous_len]);
+  return result;
+}
+

gdb/split-name.h

@@ -0,0 +1,45 @@
+/* Split a symbol name.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDB_SPLIT_NAME_H
+#define GDB_SPLIT_NAME_H
+
+#include "gdbsupport/gdb_string_view.h"
+
+/* The available styles of name splitting.  */
+
+enum class split_style
+{
+  /* No splitting - C style.  */
+  NONE,
+  /* C++ style, with "::" and template parameter intelligence.  */
+  CXX,
+  /* Split at ".".  Used by Ada, Go, D.  */
+  DOT,
+  /* Split at "__".  Used by Ada encoded names.  */
+  UNDERSCORE,
+};
+
+/* Split NAME into components at module boundaries.  STYLE indicates
+   which style of splitting to use.  */
+
+extern std::vector<gdb::string_view> split_name (const char *name,
+						 split_style style);
+
+#endif /* GDB_SPLIT_NAME_H */

gdb/symtab.h

@@ -36,6 +36,7 @@
 #include "gdbsupport/iterator-range.h"
 #include "completer.h"
 #include "gdb-demangle.h"
+#include "split-name.h"
 
 /* Opaque declarations.  */
 struct ui_file;
@@ -121,6 +122,21 @@ class ada_lookup_name_info final
   bool verbatim_p () const
   { return m_verbatim_p; }
 
+  /* A wrapper for ::split_name that handles some Ada-specific
+     peculiarities.  */
+  std::vector<gdb::string_view> split_name () const
+  {
+    if (m_verbatim_p || m_standard_p)
+      {
+	std::vector<gdb::string_view> result;
+	if (m_standard_p)
+	  result.emplace_back ("standard");
+	result.emplace_back (m_encoded_name);
+	return result;
+      }
+    return ::split_name (m_encoded_name.c_str (), split_style::UNDERSCORE);
+  }
+
 private:
   /* The Ada-encoded lookup name.  */
   std::string m_encoded_name;
@@ -272,6 +288,27 @@ class lookup_name_info final
       }
   }
 
+  /* A wrapper for ::split_name (see split-name.h) that splits this
+     name, and that handles any language-specific peculiarities.  */  
+  std::vector<gdb::string_view> split_name (language lang) const
+  {
+    if (lang == language_ada)
+      return ada ().split_name ();
+    split_style style = split_style::NONE;
+    switch (lang)
+      {
+      case language_cplus:
+      case language_rust:
+	style = split_style::CXX;
+	break;
+      case language_d:
+      case language_go:
+	style = split_style::DOT;
+	break;
+      }
+    return ::split_name (language_lookup_name (lang), style);
+  }
+
   /* Get the Ada-specific lookup info.  */
   const ada_lookup_name_info &ada () const
   {