commit 1ccb1182ef88cf81856398dd13002febebb9c9a1
Author: Daniel Swanson <popcorn.tomato.dude@gmail.com>
Date:   Wed Jul 7 14:35:01 2021 -0500

    escape special characters in regexes and compile them at build time

diff --git a/apertium/transfer_regex.cc b/apertium/transfer_regex.cc
index bc72409..642caad 100644
--- a/apertium/transfer_regex.cc
+++ b/apertium/transfer_regex.cc
@@ -67,11 +67,14 @@ unbuildTrie(TrieNode* root)
     }
   }
   UString ret;
+  if (root->c == '+' || root->c == '*' || root->c == '?' || root->c == '.') {
+    ret += '\\';
+  }
   ret += root->c;
   if (groups.empty()) {
     return ret;
   } else if (groups.size() == 1) {
-    if (root->end && groups[0][0] != '(') {
+    if (root->end && groups[0].size() > 1 && groups[0][0] != '(') {
       ret += '('; ret += '?'; ret += ':';
       ret += groups[0];
       ret += ')';
diff --git a/apertium/trx_reader.cc b/apertium/trx_reader.cc
index e400cc0..c742d86 100644
--- a/apertium/trx_reader.cc
+++ b/apertium/trx_reader.cc
@@ -21,6 +21,7 @@
 #include <cstdlib>
 #include <iostream>
 #include <apertium/transfer_regex.h>
+#include <apertium/apertium_re.h>
 
 UString const TRXReader::ANY_TAG         = "<ANY_TAG>"_u;
 UString const TRXReader::ANY_CHAR        = "<ANY_CHAR>"_u;
@@ -343,6 +344,9 @@ TRXReader::procDefAttrs()
       else
       {
         td.getAttrItems()[attrname] = optimize_regex(items);
+        // compile it now to check for errors
+        ApertiumRE r;
+        r.compile(td.getAttrItems()[attrname]);
         items.clear();
         attrname.clear();
       }