From 4a37c3bea7a36190ff515f1b4b5fb8c1b26886d3 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 14 Apr 2026 12:45:23 +0300
Subject: [PATCH] cgen: Variable declarations after `continue  <label>` cause
 builder error with `-cc gcc -cstrict` (fixes #19973)

---
 vlib/v/gen/c/cgen.v                           | 13 +++-
 vlib/v/gen/c/for.v                            | 17 ++++
 vlib/v/gen/c/labelled_continue_scope_test.v   | 55 +++++++++++++
 .../gen/c/testdata/labelled_continue_scope.vv | 78 +++++++++++++++++++
 4 files changed, 162 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/gen/c/labelled_continue_scope_test.v
 create mode 100644 vlib/v/gen/c/testdata/labelled_continue_scope.vv

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index f65d25051..660bd0c73 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -8089,6 +8089,14 @@ fn (mut g Gen) gen_hash_stmts_in_top() {
 	g.postinclude_nodes.clear()
 }
 
+fn labeled_continue_flag_name(label string) string {
+	return 'v__labeled_continue_${label}'
+}
+
+fn labeled_continue_entry_label_name(label string) string {
+	return '${label}__continue_entry'
+}
+
 fn (mut g Gen) branch_stmt(node ast.BranchStmt) {
 	if node.label != '' {
 		x := g.labeled_loops[node.label] or {
@@ -8116,7 +8124,10 @@ fn (mut g Gen) branch_stmt(node ast.BranchStmt) {
 		if node.kind == .key_break {
 			g.writeln('goto ${node.label}__break;')
 		} else {
-			g.writeln('goto ${node.label}__continue;')
+			continue_flag := labeled_continue_flag_name(node.label)
+			continue_entry_label := labeled_continue_entry_label_name(node.label)
+			g.writeln('${continue_flag} = true;')
+			g.writeln('goto ${continue_entry_label};')
 		}
 	} else {
 		inner_loop := g.inner_loop
diff --git a/vlib/v/gen/c/for.v b/vlib/v/gen/c/for.v
index 722f5caa0..858c848fd 100644
--- a/vlib/v/gen/c/for.v
+++ b/vlib/v/gen/c/for.v
@@ -21,6 +21,19 @@ fn for_in_val_type(base_type ast.Type, is_mut bool, is_ref bool) ast.Type {
 	return base_type
 }
 
+// A labeled continue jumps back to this gate instead of forward over later
+// declarations in the loop body, which avoids gcc -Wjump-misses-init.
+fn (mut g Gen) write_labeled_continue_gate(label string, prefix string) {
+	if label.len == 0 {
+		return
+	}
+	continue_flag := labeled_continue_flag_name(label)
+	continue_entry_label := labeled_continue_entry_label_name(label)
+	g.writeln('${prefix}bool ${continue_flag} = false;')
+	g.writeln('${prefix}${continue_entry_label}: {}')
+	g.writeln('${prefix}if (${continue_flag}) goto ${label}__continue;')
+}
+
 fn (mut g Gen) for_c_stmt(node ast.ForCStmt) {
 	g.loop_depth++
 	if node.is_multi {
@@ -56,6 +69,7 @@ fn (mut g Gen) for_c_stmt(node ast.ForCStmt) {
 		}
 		g.is_vlines_enabled = true
 		g.inside_for_c_stmt = false
+		g.write_labeled_continue_gate(node.label, '')
 		g.stmts(node.stmts)
 		if node.label.len > 0 {
 			g.writeln('${node.label}__continue: {}')
@@ -112,6 +126,7 @@ fn (mut g Gen) for_c_stmt(node ast.ForCStmt) {
 		g.skip_stmt_pos = false
 		g.is_vlines_enabled = true
 		g.inside_for_c_stmt = false
+		g.write_labeled_continue_gate(node.label, '')
 		g.stmts(node.stmts)
 		if node.label.len > 0 {
 			g.writeln('${node.label}__continue: {}')
@@ -141,6 +156,7 @@ fn (mut g Gen) for_stmt(node ast.ForStmt) {
 		g.indent--
 	}
 	g.is_vlines_enabled = true
+	g.write_labeled_continue_gate(node.label, '\t')
 	g.stmts(node.stmts)
 	if node.label.len > 0 {
 		g.writeln('\t${node.label}__continue: {}')
@@ -789,6 +805,7 @@ fn (mut g Gen) for_in_stmt(node_ ast.ForInStmt) {
 		typ_str := g.table.type_to_str(node.cond_type)
 		g.error('for in: unhandled symbol `${node.cond}` of type `${typ_str}`', node.pos)
 	}
+	g.write_labeled_continue_gate(node.label, '\t')
 	g.stmts(node.stmts)
 	if node.label.len > 0 {
 		g.writeln('\t${node.label}__continue: {}')
diff --git a/vlib/v/gen/c/labelled_continue_scope_test.v b/vlib/v/gen/c/labelled_continue_scope_test.v
new file mode 100644
index 000000000..34fa13d97
--- /dev/null
+++ b/vlib/v/gen/c/labelled_continue_scope_test.v
@@ -0,0 +1,55 @@
+import os
+
+const vexe = @VEXE
+
+const vroot = os.real_path(@VMODROOT)
+
+const labelled_continue_scope_testdata = os.join_path(vroot, 'vlib/v/gen/c/testdata/labelled_continue_scope.vv')
+
+struct LabelledContinueCase {
+	label    string
+	var_name string
+}
+
+fn test_labelled_continue_targets_reenter_at_the_loop_gate() {
+	os.chdir(vroot) or {}
+	cmd := '${os.quoted_path(vexe)} -o - ${os.quoted_path(labelled_continue_scope_testdata)}'
+	compilation := os.execute(cmd)
+	assert compilation.exit_code == 0
+	generated_c := compilation.output.replace('\r\n', '\n')
+	cases := [
+		LabelledContinueCase{'range_outer', 'issue_19973_range_var'},
+		LabelledContinueCase{'cond_outer', 'issue_19973_cond_var'},
+		LabelledContinueCase{'c_outer', 'issue_19973_c_var'},
+		LabelledContinueCase{'c_multi_outer', 'issue_19973_c_multi_var'},
+	]
+	for tc in cases {
+		continue_flag := 'v__labeled_continue_${tc.label}'
+		continue_entry_label := '${tc.label}__continue_entry: {}'
+		continue_label := '${tc.label}__continue: {}'
+		continue_gate := 'if (${continue_flag}) goto ${tc.label}__continue;'
+		continue_assignment := '${continue_flag} = true;'
+		continue_goto := 'goto ${tc.label}__continue_entry;'
+		var_decl := 'string ${tc.var_name} ='
+		assert generated_c.contains('bool ${continue_flag} = false;')
+		assert generated_c.contains(continue_entry_label)
+		assert generated_c.contains(continue_gate)
+		assert generated_c.contains(continue_assignment)
+		assert generated_c.contains(continue_goto)
+		flag_idx := generated_c.index('bool ${continue_flag} = false;') or {
+			panic('missing continue flag for `${tc.label}`')
+		}
+		entry_idx := generated_c.index(continue_entry_label) or {
+			panic('missing continue entry label for `${tc.label}`')
+		}
+		var_idx := generated_c.index(var_decl) or {
+			panic('missing declaration for `${tc.var_name}`')
+		}
+		label_idx := generated_c.index(continue_label) or {
+			panic('missing continue label for `${tc.label}`')
+		}
+		assert flag_idx < entry_idx
+		assert entry_idx < var_idx
+		assert var_idx < label_idx
+	}
+}
diff --git a/vlib/v/gen/c/testdata/labelled_continue_scope.vv b/vlib/v/gen/c/testdata/labelled_continue_scope.vv
new file mode 100644
index 000000000..f68f659cb
--- /dev/null
+++ b/vlib/v/gen/c/testdata/labelled_continue_scope.vv
@@ -0,0 +1,78 @@
+fn range_loop() {
+	range_outer: for i in 0 .. 2 {
+		for j in 0 .. 2 {
+			if i < 2 && j == 1 {
+				continue range_outer
+			}
+		}
+		issue_19973_range_var := 'issue-19973'
+		for k in 0 .. 2 {
+			if k == 1 {
+				println(issue_19973_range_var)
+				continue range_outer
+			}
+		}
+	}
+}
+
+fn cond_loop() {
+	mut i := 0
+	cond_outer: for i < 2 {
+		for j in 0 .. 2 {
+			if i < 2 && j == 1 {
+				i++
+				continue cond_outer
+			}
+		}
+		issue_19973_cond_var := 'issue-19973'
+		for k in 0 .. 2 {
+			if k == 1 {
+				i++
+				println(issue_19973_cond_var)
+				continue cond_outer
+			}
+		}
+		i++
+	}
+}
+
+fn c_loop() {
+	c_outer: for i := 0; i < 2; i++ {
+		for j := 0; j < 2; j++ {
+			if i < 2 && j == 1 {
+				continue c_outer
+			}
+		}
+		issue_19973_c_var := 'issue-19973'
+		for k := 0; k < 2; k++ {
+			if k == 1 {
+				println(issue_19973_c_var)
+				continue c_outer
+			}
+		}
+	}
+}
+
+fn c_multi_loop() {
+	c_multi_outer: for i, j := 0, 0; i < 2; i++, j++ {
+		for k in 0 .. 2 {
+			if i + j < 3 && k == 1 {
+				continue c_multi_outer
+			}
+		}
+		issue_19973_c_multi_var := 'issue-19973'
+		for k in 0 .. 2 {
+			if j >= 0 && k == 1 {
+				println(issue_19973_c_multi_var)
+				continue c_multi_outer
+			}
+		}
+	}
+}
+
+fn main() {
+	range_loop()
+	cond_loop()
+	c_loop()
+	c_multi_loop()
+}
-- 
2.39.5