1 files changed, 129 insertions, 0 deletions
diff --git a/gdbsupport/string-set.h b/gdbsupport/string-set.h
new file mode 100644
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+++ b/gdbsupport/string-set.h
@@ -0,0 +1,129 @@
+/* String-interning set
+
+   Copyright (C) 2025 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 GDBSUPPORT_STRING_SET_H
+#define GDBSUPPORT_STRING_SET_H
+
+#include "gdbsupport/unordered_set.h"
+#include <string_view>
+
+namespace gdb
+{
+
+/* This is a string-interning set.  It manages storage for strings,
+   ensuring that just a single copy of a given string is kept.  The
+   underlying C string will remain valid for the lifetime of this
+   object.  */
+
+class string_set
+{
+public:
+
+  /* Insert STR into this set.  Returns a pointer to the interned
+     string.  */
+  const char *insert (const char *str)
+  {
+    /* We need to take the length to hash the string anyway, so it's
+       convenient to just wrap it here.  */
+    return insert (std::string_view (str));
+  }
+
+  /* An overload accepting a string view.  */
+  const char *insert (std::string_view str)
+  {
+    return m_set.insert (str).first->get ();
+  }
+
+  /* An overload that takes ownership of the string.  */
+  const char *insert (gdb::unique_xmalloc_ptr<char> str)
+  {
+    return m_set.insert (local_string (std::move (str))).first->get ();
+  }
+
+private:
+
+  /* The type of string we store.  Note that we do not store
+     std::string here to avoid the small-string optimization
+     invalidating a pointer on rehash.  */
+  struct local_string
+  {
+    explicit local_string (std::string_view str)
+      : contents (xstrndup (str.data (), str.size ())),
+	len (str.size ())
+    { }
+
+    explicit local_string (gdb::unique_xmalloc_ptr<char> str)
+      : contents (std::move (str)),
+	len (strlen (contents.get ()))
+    { }
+
+    const char *get () const
+    { return contents.get (); }
+
+    std::string_view as_view () const
+    { return std::string_view (contents.get (), len); }
+
+    /* \0-terminated string contents.  */
+    gdb::unique_xmalloc_ptr<char> contents;
+    /* Length of the string.  */
+    size_t len;
+  };
+
+  /* Equality object for the set.  */
+  struct str_eq
+  {
+    using is_transparent = void;
+
+    bool operator() (std::string_view lhs, const local_string &rhs)
+      const noexcept
+    {
+      return lhs == rhs.as_view ();
+    }
+
+    bool operator() (const local_string &lhs, const local_string &rhs)
+      const noexcept
+    {
+      return (*this) (lhs.as_view (), rhs);
+    }
+  };
+
+  /* Hash object for the set.  */
+  struct str_hash
+  {
+    using is_transparent = void;
+    using is_avalanching = void;
+
+    uint64_t operator() (const local_string &rhs) const noexcept
+    {
+      return (*this) (rhs.as_view ());
+    }
+
+    uint64_t operator() (std::string_view rhs) const noexcept
+    {
+      return ankerl::unordered_dense::hash<std::string_view> () (rhs);
+    }
+  };
+
+  /* The strings.  */
+  gdb::unordered_set<local_string, str_hash, str_eq> m_set;
+};
+
+}
+
+#endif /* GDBSUPPORT_STRING_SET_H */