From 64e9d8e805538b430f1812d627f6f395f0b25b70 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 14:57:14 +0300
Subject: [PATCH] cgen: fix hot reload failure when using time.now() in
 interpolation (fixes #19456)

---
 vlib/v/gen/c/str_intp.v                       | 36 +++++++++++++++++--
 ...d_string_interpolation_codegen.c.must_have |  2 ++
 ...ive_shared_string_interpolation_codegen.vv | 14 ++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.vv

diff --git a/vlib/v/gen/c/str_intp.v b/vlib/v/gen/c/str_intp.v
index 455bfbec0..720bde9e9 100644
--- a/vlib/v/gen/c/str_intp.v
+++ b/vlib/v/gen/c/str_intp.v
@@ -454,6 +454,9 @@ fn (mut g Gen) str_val(node ast.StringInterLiteral, i int, fmts []u8) {
 			g.inside_opt_or_res = old_inside_opt_or_res
 			g.write('.data))')
 		} else {
+			if g.gen_windows_liveshared_string_tmp(expr, exp_typ) {
+				return
+			}
 			g.gen_expr_to_string(expr, exp_typ)
 		}
 	} else if typ.is_number() || typ.is_pointer() || fmt == `d` {
@@ -783,7 +786,9 @@ fn (mut g Gen) gen_simple_string_inter_literal(node ast.StringInterLiteral, fmts
 		}
 	}
 	if node.exprs.len == 1 && node.vals.len == 2 && node.vals[0].len == 0 && node.vals[1].len == 0 {
-		g.gen_expr_to_string(node.exprs[0], node.expr_types[0])
+		if !g.gen_windows_liveshared_string_tmp(node.exprs[0], node.expr_types[0]) {
+			g.gen_expr_to_string(node.exprs[0], node.expr_types[0])
+		}
 		return true
 	}
 	mut part_count := 0
@@ -815,10 +820,37 @@ fn (mut g Gen) gen_simple_string_inter_literal(node ast.StringInterLiteral, fmts
 			if written_parts > 0 {
 				g.write(', ')
 			}
-			g.gen_expr_to_string(node.exprs[i], node.expr_types[i])
+			if !g.gen_windows_liveshared_string_tmp(node.exprs[i], node.expr_types[i]) {
+				g.gen_expr_to_string(node.exprs[i], node.expr_types[i])
+			}
 			written_parts++
 		}
 	}
 	g.write('}))')
 	return true
 }
+
+fn (g &Gen) should_materialize_windows_liveshared_string(expr ast.Expr, typ ast.Type) bool {
+	if g.pref.os != .windows || !g.pref.is_liveshared || g.inside_const {
+		return false
+	}
+	// The live shared DLL path on Windows is sensitive to nested string-returning
+	// expressions inside interpolation compound literals, so lower them via temps.
+	if typ == ast.string_type {
+		return expr !is ast.Ident && expr !is ast.StringLiteral && expr !is ast.SelectorExpr
+			&& expr !is ast.ComptimeSelector
+	}
+	return true
+}
+
+fn (mut g Gen) gen_windows_liveshared_string_tmp(expr ast.Expr, typ ast.Type) bool {
+	if !g.should_materialize_windows_liveshared_string(expr, typ) {
+		return false
+	}
+	past := g.past_tmp_var_new()
+	g.write('string ${past.tmp_var} = ')
+	g.gen_expr_to_string(expr, typ)
+	g.writeln(';')
+	g.past_tmp_var_done(past)
+	return true
+}
diff --git a/vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.c.must_have b/vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.c.must_have
new file mode 100644
index 000000000..002524cf4
--- /dev/null
+++ b/vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.c.must_have
@@ -0,0 +1,2 @@
+string _t1 = time__Time_str(t);
+builtin__println(builtin__string_plus_many(2, _MOV((string[2]){_S("Time: "),_t1})));
diff --git a/vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.vv b/vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.vv
new file mode 100644
index 000000000..d892709bc
--- /dev/null
+++ b/vlib/v/gen/c/testdata/live_shared_string_interpolation_codegen.vv
@@ -0,0 +1,14 @@
+// vtest vflags: -os windows -sharedlive -shared
+module main
+
+import time
+
+@[live]
+fn print_message2() {
+	t := time.now()
+	println('Time: ${t}')
+}
+
+fn main() {
+	print_message2()
+}
-- 
2.39.5