6 files changed, 92 insertions, 11 deletions
diff --git a/test/cases/compile_errors/int_literal_passed_as_variadic_arg.zig b/test/cases/compile_errors/int_literal_passed_as_variadic_arg.zig
deleted file mode 100644
index be9ffaa884..0000000000
--- a/test/cases/compile_errors/int_literal_passed_as_variadic_arg.zig
+++ /dev/null
@@ -1,11 +0,0 @@
-extern fn printf([*:0]const u8, ...) c_int;
-
-pub export fn entry() void {
-    _ = printf("%d %d %d %d\n", 1, 2, 3, 4);
-}
-
-// error
-// backend=stage2
-// target=native
-//
-// :4:33: error: integer and float literals in var args function must be casted
diff --git a/test/cases/compile_errors/variadic_arg_validation.zig b/test/cases/compile_errors/variadic_arg_validation.zig
new file mode 100644
index 0000000000..830d3a0877
--- /dev/null
+++ b/test/cases/compile_errors/variadic_arg_validation.zig
@@ -0,0 +1,29 @@
+extern fn printf([*:0]const u8, ...) c_int;
+
+pub export fn entry() void {
+    _ = printf("%d %d %d %d\n", 1, 2, 3, 4);
+}
+
+pub export fn entry1() void {
+    var arr: [2]u8 = undefined;
+    _ = printf("%d\n", arr);
+}
+
+pub export fn entry2() void {
+    _ = printf("%d\n", @as(u48, 2));
+}
+
+pub export fn entry3() void {
+    _ = printf("%d\n", {});
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :4:33: error: integer and float literals passed variadic function must be casted to a fixed-size number type
+// :9:24: error: arrays must be passed by reference to variadic function
+// :13:24: error: cannot pass 'u48' to variadic function
+// :13:24: note: only integers with power of two bits are extern compatible
+// :17:24: error: cannot pass 'void' to variadic function
+// :17:24: note: 'void' is a zero bit type; for C 'void' use 'anyopaque'
diff --git a/test/standalone.zig b/test/standalone.zig
index bfd683ec4c..26af0d5da5 100644
--- a/test/standalone.zig
+++ b/test/standalone.zig
@@ -66,6 +66,7 @@ pub fn addCases(cases: *tests.StandaloneContext) void {
     if (builtin.os.tag == .linux) {
         cases.addBuildFile("test/standalone/pie/build.zig", .{});
     }
+    cases.addBuildFile("test/standalone/issue_12706/build.zig", .{});
 
     // Ensure the development tools are buildable.
 
diff --git a/test/standalone/issue_12706/build.zig b/test/standalone/issue_12706/build.zig
new file mode 100644
index 0000000000..d84160a4f4
--- /dev/null
+++ b/test/standalone/issue_12706/build.zig
@@ -0,0 +1,39 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const Builder = std.build.Builder;
+const CrossTarget = std.zig.CrossTarget;
+
+// TODO integrate this with the std.build executor API
+fn isRunnableTarget(t: CrossTarget) bool {
+    if (t.isNative()) return true;
+
+    return (t.getOsTag() == builtin.os.tag and
+        t.getCpuArch() == builtin.cpu.arch);
+}
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+    const target = b.standardTargetOptions(.{});
+
+    const exe = b.addExecutable("main", "main.zig");
+    exe.setBuildMode(mode);
+    exe.install();
+
+    const c_sources = [_][]const u8{
+        "test.c",
+    };
+
+    exe.addCSourceFiles(&c_sources, &.{});
+    exe.linkLibC();
+
+    exe.setTarget(target);
+    b.default_step.dependOn(&exe.step);
+
+    const test_step = b.step("test", "Test the program");
+    if (isRunnableTarget(target)) {
+        const run_cmd = exe.run();
+        test_step.dependOn(&run_cmd.step);
+    } else {
+        test_step.dependOn(&exe.step);
+    }
+}
diff --git a/test/standalone/issue_12706/main.zig b/test/standalone/issue_12706/main.zig
new file mode 100644
index 0000000000..b40c997561
--- /dev/null
+++ b/test/standalone/issue_12706/main.zig
@@ -0,0 +1,12 @@
+const std = @import("std");
+extern fn testFnPtr(n: c_int, ...) void;
+
+const val: c_int = 123;
+
+fn func(a: c_int) callconv(.C) void {
+    std.debug.assert(a == val);
+}
+
+pub fn main() void {
+    testFnPtr(2, func, val);
+}
diff --git a/test/standalone/issue_12706/test.c b/test/standalone/issue_12706/test.c
new file mode 100644
index 0000000000..30b5c62697
--- /dev/null
+++ b/test/standalone/issue_12706/test.c
@@ -0,0 +1,11 @@
+#include <stdarg.h>
+
+void testFnPtr(int n, ...) {
+    va_list ap;
+    va_start(ap, n);
+
+    void (*fnPtr)(int) = va_arg(ap, void (*)(int));
+    int arg = va_arg(ap, int);
+    fnPtr(arg);
+    va_end(ap);
+}
+\ No newline at end of file