Merge pull request #52370 from bruvzg/realloc_paren_stack

2 files changed, 20 insertions, 2 deletions

diff --git a/modules/text_server_adv/script_iterator.cpp b/modules/text_server_adv/script_iterator.cpp
index f9bbd25a5f..d1e849def8 100644
--- a/modules/text_server_adv/script_iterator.cpp
+++ b/modules/text_server_adv/script_iterator.cpp
@@ -30,6 +30,8 @@
 
 #include "script_iterator.h"
 
+// This implementation is derived from ICU: icu4c/source/extra/scrptrun/scrptrun.cpp
+
 bool ScriptIterator::same_script(int32_t p_script_one, int32_t p_script_two) {
 	return p_script_one <= USCRIPT_INHERITED || p_script_two <= USCRIPT_INHERITED || p_script_one == p_script_two;
 }
@@ -48,7 +50,8 @@ ScriptIterator::ScriptIterator(const String &p_string, int p_start, int p_length
 		p_start = 0;
 	}
 
-	ParenStackEntry paren_stack[128];
+	int paren_size = PAREN_STACK_DEPTH;
+	ParenStackEntry *paren_stack = (ParenStackEntry *)memalloc(paren_size * sizeof(ParenStackEntry));
 
 	int script_start;
 	int script_end = p_start;
@@ -64,13 +67,22 @@ ScriptIterator::ScriptIterator(const String &p_string, int p_start, int p_length
 			UChar32 ch = str[script_end];
 			UScriptCode sc = uscript_getScript(ch, &err);
 			if (U_FAILURE(err)) {
+				memfree(paren_stack);
 				ERR_FAIL_MSG(u_errorName(err));
 			}
 			if (u_getIntPropertyValue(ch, UCHAR_BIDI_PAIRED_BRACKET_TYPE) != U_BPT_NONE) {
 				if (u_getIntPropertyValue(ch, UCHAR_BIDI_PAIRED_BRACKET_TYPE) == U_BPT_OPEN) {
-					paren_stack[++paren_sp].pair_index = ch;
+					// If it's an open character, push it onto the stack.
+					paren_sp++;
+					if (unlikely(paren_sp >= paren_size)) {
+						// If the stack is full, allocate more space to handle deeply nested parentheses. This is unlikely to happen with any real text.
+						paren_size += PAREN_STACK_DEPTH;
+						paren_stack = (ParenStackEntry *)memrealloc(paren_stack, paren_size * sizeof(ParenStackEntry));
+					}
+					paren_stack[paren_sp].pair_index = ch;
 					paren_stack[paren_sp].script_code = script_code;
 				} else if (paren_sp >= 0) {
+					// If it's a close character, find the matching open on the stack, and use that script code. Any non-matching open characters above it on the stack will be poped.
 					UChar32 paired_ch = u_getBidiPairedBracket(ch);
 					while (paren_sp >= 0 && paren_stack[paren_sp].pair_index != paired_ch) {
 						paren_sp -= 1;
@@ -87,11 +99,13 @@ ScriptIterator::ScriptIterator(const String &p_string, int p_start, int p_length
 			if (same_script(script_code, sc)) {
 				if (script_code <= USCRIPT_INHERITED && sc > USCRIPT_INHERITED) {
 					script_code = sc;
+					// Now that we have a final script code, fix any open characters we pushed before we knew the script code.
 					while (start_sp < paren_sp) {
 						paren_stack[++start_sp].script_code = script_code;
 					}
 				}
 				if ((u_getIntPropertyValue(ch, UCHAR_BIDI_PAIRED_BRACKET_TYPE) == U_BPT_CLOSE) && paren_sp >= 0) {
+					// If this character is a close paired character pop the matching open character from the stack.
 					paren_sp -= 1;
 					if (start_sp >= 0) {
 						start_sp -= 1;
@@ -109,4 +123,6 @@ ScriptIterator::ScriptIterator(const String &p_string, int p_start, int p_length
 
 		script_ranges.push_back(rng);
 	} while (script_end < p_length);
+
+	memfree(paren_stack);
 }
diff --git a/modules/text_server_adv/script_iterator.h b/modules/text_server_adv/script_iterator.h
index 896a0e5c15..5efd40f7c4 100644
--- a/modules/text_server_adv/script_iterator.h
+++ b/modules/text_server_adv/script_iterator.h
@@ -43,6 +43,8 @@
 #include <hb.h>
 
 class ScriptIterator {
+	static const int PAREN_STACK_DEPTH = 128;
+
 public:
 	struct ScriptRange {
 		int start = 0;