From 4c6a6f361f0869216c533d1d5f2e7063014ed10e Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 25 Mar 2026 16:42:17 +0300
Subject: [PATCH] cgen: fix initializer element is not a compile-time constant
 (fixes #25684)

---
 vlib/v/gen/c/assign.v           | 37 +++++++++++++++++++++++++++++++++
 vlib/v/tests/static_vars_test.v | 19 +++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/vlib/v/gen/c/assign.v b/vlib/v/gen/c/assign.v
index d734552fd..fa2a106f9 100644
--- a/vlib/v/gen/c/assign.v
+++ b/vlib/v/gen/c/assign.v
@@ -278,6 +278,39 @@ fn (mut g Gen) expr_with_opt(expr ast.Expr, expr_typ ast.Type, ret_typ ast.Type)
 	return ''
 }
 
+fn (g &Gen) static_init_guard_name(pos token.Pos) string {
+	return '_vstatic_init_${pos.pos}'
+}
+
+fn (mut g Gen) gen_static_decl_runtime_init(node ast.AssignStmt, left ast.Expr, left_type ast.Type, right ast.Expr, right_type ast.Type) bool {
+	if node.left.len != 1 || node.right.len != 1 || g.inside_ternary != 0 {
+		return false
+	}
+	if left !is ast.Ident {
+		return false
+	}
+	guard_name := g.static_init_guard_name(left.pos())
+	g.writeln(';')
+	g.writeln('static bool ${guard_name};')
+	g.writeln('if (!${guard_name}) {')
+	g.indent++
+	g.writeln('${guard_name} = true;')
+	old_is_assign_lhs := g.is_assign_lhs
+	g.is_assign_lhs = false
+	g.assign_stmt(ast.AssignStmt{
+		op:          .assign
+		pos:         node.pos
+		left:        [left]
+		right:       [right]
+		left_types:  [left_type]
+		right_types: [right_type]
+	})
+	g.is_assign_lhs = old_is_assign_lhs
+	g.indent--
+	g.writeln('}')
+	return true
+}
+
 fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 	mut node := unsafe { node_ }
 	if node.is_static {
@@ -1487,6 +1520,10 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 				g.out.write_string(util.tabs(g.indent))
 				g.expr(left)
 			}
+			if is_decl && node.is_static
+				&& g.gen_static_decl_runtime_init(node, left, var_type, val, val_type) {
+				continue
+			}
 			g.is_assign_lhs = false
 			if left is ast.IndexExpr && g.cur_indexexpr.len > 0 {
 				cur_indexexpr = g.cur_indexexpr.index(left.pos().pos)
diff --git a/vlib/v/tests/static_vars_test.v b/vlib/v/tests/static_vars_test.v
index de286afa6..179705b45 100644
--- a/vlib/v/tests/static_vars_test.v
+++ b/vlib/v/tests/static_vars_test.v
@@ -27,3 +27,22 @@ fn test_static_vars_in_unsafe_blocks() {
 	assert f() == 2
 	dump(f()) // 3
 }
+
+@[unsafe]
+fn next_fib() int {
+	mut static fibs := []int{}
+	if fibs.len == 0 {
+		fibs << 1
+		fibs << 1
+	} else {
+		fibs << fibs[fibs.len - 1] + fibs[fibs.len - 2]
+	}
+	return fibs[fibs.len - 1]
+}
+
+fn test_static_vars_with_array_initializers() {
+	assert unsafe { next_fib() } == 1
+	assert unsafe { next_fib() } == 2
+	assert unsafe { next_fib() } == 3
+	assert unsafe { next_fib() } == 5
+}
-- 
2.39.5