std::set::find only appeared in C++20. Rather use std::set::find for compatibility.
if (docbookTag == "SPECIFIC") {
delayedTags[match[1]] = match[2];
} else {
- if (alreadyOutputDocBookTags.contains(docbookTag)) {
+ if (alreadyOutputDocBookTags.find(docbookTag) != alreadyOutputDocBookTags.end()) {
xs << XMLStream::ESCAPE_NONE <<
from_utf8("<!-- Several similar tags in the reference for ") + from_utf8(docbookTag) +
from_utf8(". New tag: ") + from_utf8(match[1]) + from_utf8(". Corresponding value: ") +