explicit c++20

DESCRIPTION

@@ -2,7 +2,7 @@ Package: udpipe
 Type: Package
 Title: Tokenization, Parts of Speech Tagging, Lemmatization and Dependency
     Parsing with the 'UDPipe' 'NLP' Toolkit
-Version: 0.8.15
+Version: 0.8.16
 Maintainer: Jan Wijffels <jwijffels@bnosac.be>
 Authors@R: c(
     person('Jan', 'Wijffels', role = c('aut', 'cre', 'cph'), email = 'jwijffels@bnosac.be', comment = 'R wrapper'), 

NEWS.md

@@ -1,3 +1,7 @@
+## CHANGES IN udpipe VERSION 0.8.16
+
+- Fix on the declaration of persistent_unordered_map for C++20
+
 ## CHANGES IN udpipe VERSION 0.8.15
 
 - Drop C++11 from Makevars

src/udpipe.cpp

@@ -3492,7 +3492,7 @@ class persistent_unordered_map {
   inline const unsigned char* data_start(int len) const;
 
   // Creation functions
-  persistent_unordered_map() {}
+  inline persistent_unordered_map();
   template <class Entry, class EntryEncode>
   persistent_unordered_map(const unordered_map<string, Entry>& map, double load_factor, EntryEncode entry_encode);
   template <class Entry, class EntryEncode>
@@ -3634,6 +3634,8 @@ const unsigned char* persistent_unordered_map::data_start(int len) const {
   return unsigned(len) < hashes.size() ? hashes[len].data.data() : nullptr;
 }
 
+persistent_unordered_map::persistent_unordered_map() {}
+
 void persistent_unordered_map::resize(unsigned elems) {
   if (hashes.size() == 0) hashes.emplace_back(1);
   else if (hashes.size() == 1) hashes.emplace_back(1<<8);