1 files changed, 37 insertions, 0 deletions
diff --git a/common/templates/clang/src/test.zig b/common/templates/clang/src/test.zig
new file mode 100644
index 0000000..49ff4d0
--- /dev/null
+++ b/common/templates/clang/src/test.zig
@@ -0,0 +1,37 @@
+const std = @import("std");
+
+extern fn hello_world(action: [*c]const u8) void;
+
+// We use global static memory for our trap. 
+// Because this test runs in a single thread and we know the string is tiny, 
+var captured_output: [64]u8 = undefined;
+var captured_len: usize = 0;
+
+// Exported to the dynamic symbol table so dlsym() can find it.
+// Signature must accept two pointers to perfectly map to the 
+// System V ABI hardware registers used by: dynamic_eval("%s", result);
+// CPU registers (RDI and RSI) that the C code will use when calling this via variadic arguments.
+export fn test_capture_sink(fmt: [*c]const u8, msg: [*c]const u8) void {
+    // We intentionally ignore the format string ("%s") sitting in the first register
+    _ = fmt; 
+
+    // std.mem.span walks the raw C pointer until it finds the \0 null terminator.
+    // It doesn't allocate memory; it just calculates the length so we have a safe Zig slice.
+    const slice = std.mem.span(msg);
+    
+    // Copy the raw bytes directly from the C memory space into our static Zig buffer.
+    @memcpy(captured_output[0..slice.len], slice);
+    captured_len = slice.len;
+}
+
+test "catfish dlsym eval" {
+    // We hand our C code the name of our exported Zig function. 
+    // The C code will parse its own __func__, ask the OS to find "test_capture_sink",
+    // and execute it, throwing the parsed string right back into our global variables.
+    hello_world("test_capture_sink");
+
+    // Reconstruct a strict Zig string from the exact number of bytes we captured
+    const result = captured_output[0..captured_len];
+    
+    try std.testing.expectEqualStrings("Hello World!\n", result);
+}