From 8fb3697916ec2a58a63bbcee65cb1bf37253a8cd Mon Sep 17 00:00:00 2001
From: aaronp64 <aaronp.code@gmail.com>
Date: Mon, 12 May 2025 11:42:41 -0400
Subject: [PATCH] Avoid single character String allocations when appending
 characters

Removed calls to String::chr() when appending characters to Strings in Expression, Resource, and VariantParser, to avoid creating temporary Strings for each character.  Also updated the Resource case to resize String up front, since size is known.
---
 core/io/resource.cpp            | 7 +++++--
 core/math/expression.cpp        | 4 ++--
 core/variant/variant_parser.cpp | 4 ++--
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/core/io/resource.cpp b/core/io/resource.cpp
index fac829d9cb4..5b76b6a5447 100644
--- a/core/io/resource.cpp
+++ b/core/io/resource.cpp
@@ -142,15 +142,18 @@ String Resource::generate_scene_unique_id() {
 	static constexpr uint32_t char_count = ('z' - 'a');
 	static constexpr uint32_t base = char_count + ('9' - '0');
 	String id;
+	id.resize(characters + 1);
+	char32_t *ptr = id.ptrw();
 	for (uint32_t i = 0; i < characters; i++) {
 		uint32_t c = random_num % base;
 		if (c < char_count) {
-			id += String::chr('a' + c);
+			ptr[i] = ('a' + c);
 		} else {
-			id += String::chr('0' + (c - char_count));
+			ptr[i] = ('0' + (c - char_count));
 		}
 		random_num /= base;
 	}
+	ptr[characters] = '\0';
 
 	return id;
 }
diff --git a/core/math/expression.cpp b/core/math/expression.cpp
index 0bfc8def8e2..17830394422 100644
--- a/core/math/expression.cpp
+++ b/core/math/expression.cpp
@@ -408,7 +408,7 @@ Error Expression::_get_token(Token &r_token) {
 						if (reading == READING_DONE) {
 							break;
 						}
-						num += String::chr(c);
+						num += c;
 						c = GET_CHAR();
 						is_first_char = false;
 					}
@@ -435,7 +435,7 @@ Error Expression::_get_token(Token &r_token) {
 					cchar = GET_CHAR();
 
 					while (is_unicode_identifier_continue(cchar)) {
-						id += String::chr(cchar);
+						id += cchar;
 						cchar = GET_CHAR();
 					}
 
diff --git a/core/variant/variant_parser.cpp b/core/variant/variant_parser.cpp
index 7f6b9f9689a..5631f6d242d 100644
--- a/core/variant/variant_parser.cpp
+++ b/core/variant/variant_parser.cpp
@@ -1757,7 +1757,7 @@ Error VariantParser::_parse_tag(Token &token, Stream *p_stream, int &line, Strin
 				} else {
 					escaping = false;
 				}
-				r_tag.name += String::chr(c);
+				r_tag.name += c;
 			}
 		}
 
@@ -1902,7 +1902,7 @@ Error VariantParser::parse_tag_assign_eof(Stream *p_stream, int &line, String &r
 				what = tk.value;
 
 			} else if (c != '=') {
-				what += String::chr(c);
+				what += c;
 			} else {
 				r_assign = what;
 				Token token;