From d73a05aa78e289eac3408b5ddb21a32d954c26a7 Mon Sep 17 00:00:00 2001
From: Rangi <35663410+Rangi42@users.noreply.github.com>
Date: Sat, 3 Oct 2026 16:16:58 -0400
Subject: [PATCH] Fix backtraces for `REPT` nodes with quiet non-`REPT`
 ancestors (#2196)

---
 src/asm/fstack.cpp           | 22 ++++++++++++++++------
 src/link/fstack.cpp          | 22 ++++++++++++++++------
 test/asm/rept-node-names.asm |  3 +++
 test/asm/rept-node-names.err |  8 ++++++++
 test/asm/rept-node-names.inc | 10 ++++++++++
 5 files changed, 53 insertions(+), 12 deletions(-)
 create mode 100644 test/asm/rept-node-names.asm
 create mode 100644 test/asm/rept-node-names.err
 create mode 100644 test/asm/rept-node-names.inc

diff --git a/src/asm/fstack.cpp b/src/asm/fstack.cpp
index e00cc695..cde3c5ae 100644
--- a/src/asm/fstack.cpp
+++ b/src/asm/fstack.cpp
@@ -86,13 +86,23 @@ void FileStackNode::printBacktrace(uint32_t curLineNo) const {
 	traceNodes.reserve(items.size());
 	for (auto &[node, itemLineNo] : reversed(items)) {
 		if (std::holds_alternative<std::vector<uint32_t>>(node->data)) {
-			assume(!traceNodes.empty()); // REPT nodes use their parent's name
-			std::string reptName = traceNodes.back().first;
-			if (std::vector<uint32_t> const &nodeIters = node->iters(); !nodeIters.empty()) {
-				reptName.append(NODE_SEPARATOR REPT_NODE_PREFIX);
-				reptName.append(std::to_string(nodeIters.front()));
+			// REPT nodes use their first non-REPT parent's name (which may be a quiet node and
+			// thus not in `traceNodes`), followed by their REPT parents' iteration counts,
+			// followed by their own iteration count.
+			std::string reptName;
+			for (FileStackNode const *ancestor = node->parent.get();;
+			     ancestor = ancestor->parent.get()) {
+				assume(ancestor != nullptr); // The top level context cannot be a REPT
+				if (ancestor->type != NODE_REPT) {
+					reptName.append(ancestor->name());
+					break;
+				}
 			}
-			traceNodes.emplace_back(reptName, itemLineNo);
+			for (uint32_t iter : reversed(node->iters())) {
+				reptName.append(NODE_SEPARATOR REPT_NODE_PREFIX);
+				reptName.append(std::to_string(iter));
+			}
+			traceNodes.emplace_back(std::move(reptName), itemLineNo);
 		} else {
 			traceNodes.emplace_back(node->name(), itemLineNo);
 		}
diff --git a/src/link/fstack.cpp b/src/link/fstack.cpp
index 58b6e0c3..560ba35f 100644
--- a/src/link/fstack.cpp
+++ b/src/link/fstack.cpp
@@ -41,13 +41,23 @@ void FileStackNode::printBacktrace(uint32_t curLineNo) const {
 	traceNodes.reserve(items.size());
 	for (auto &[node, itemLineNo] : reversed(items)) {
 		if (std::holds_alternative<std::vector<uint32_t>>(node->data)) {
-			assume(!traceNodes.empty()); // REPT nodes use their parent's name
-			std::string reptName = traceNodes.back().first;
-			if (std::vector<uint32_t> const &nodeIters = node->iters(); !nodeIters.empty()) {
-				reptName.append(NODE_SEPARATOR REPT_NODE_PREFIX);
-				reptName.append(std::to_string(nodeIters.back()));
+			// REPT nodes use their first non-REPT parent's name (which may be a quiet node and
+			// thus not in `traceNodes`), followed by their REPT parents' iteration counts,
+			// followed by their own iteration count.
+			std::string reptName;
+			for (FileStackNode const *ancestor = node->parent;; ancestor = ancestor->parent) {
+				// The top level context cannot be a REPT (guaranteed by `readFileStackNode`)
+				assume(ancestor != nullptr);
+				if (ancestor->type != NODE_REPT) {
+					reptName.append(ancestor->name());
+					break;
+				}
 			}
-			traceNodes.emplace_back(reptName, itemLineNo);
+			for (uint32_t iter : node->iters()) {
+				reptName.append(NODE_SEPARATOR REPT_NODE_PREFIX);
+				reptName.append(std::to_string(iter));
+			}
+			traceNodes.emplace_back(std::move(reptName), itemLineNo);
 		} else {
 			traceNodes.emplace_back(node->name(), itemLineNo);
 		}
diff --git a/test/asm/rept-node-names.asm b/test/asm/rept-node-names.asm
new file mode 100644
index 00000000..88cd72de
--- /dev/null
+++ b/test/asm/rept-node-names.asm
@@ -0,0 +1,3 @@
+INCLUDE "rept-node-names.inc"
+quiet
+loud
diff --git a/test/asm/rept-node-names.err b/test/asm/rept-node-names.err
new file mode 100644
index 00000000..cca2eb3f
--- /dev/null
+++ b/test/asm/rept-node-names.err
@@ -0,0 +1,8 @@
+warning: $0 [-Wuser]
+    at rept-node-names.inc::quiet::REPT~1(3) <- rept-node-names.asm(2)
+warning: $1 [-Wuser]
+    at rept-node-names.inc::quiet::REPT~2(3) <- rept-node-names.asm(2)
+warning: $0 [-Wuser]
+    at rept-node-names.inc::loud::REPT~1(8) <- rept-node-names.inc::loud(7) <- rept-node-names.asm(3)
+warning: $1 [-Wuser]
+    at rept-node-names.inc::loud::REPT~2(8) <- rept-node-names.inc::loud(7) <- rept-node-names.asm(3)
diff --git a/test/asm/rept-node-names.inc b/test/asm/rept-node-names.inc
new file mode 100644
index 00000000..a12552e6
--- /dev/null
+++ b/test/asm/rept-node-names.inc
@@ -0,0 +1,10 @@
+MACRO? quiet
+	FOR i, 2
+		WARN "{i}"
+	ENDR
+ENDM
+MACRO loud
+	FOR i, 2
+		WARN "{i}"
+	ENDR
+ENDM