[SYCL][COMPAT] Add get_error_string_dummy() function

sycl/doc/syclcompat/README.md

@@ -1589,6 +1589,10 @@ If a `std::runtime_error` exception is caught,
 `syclcompat::error_code::default_error` is returned instead. For both cases, it
 prints the error message to the standard error stream.
 
+`get_error_string_dummy` is a dummy function introduced to assist auto
+migration. The SYCLomatic user should replace it with a real error-handling 
+function. SYCL reports errors using exceptions and does not use error codes.
+
 ``` c++
 namespace syclcompat {
 
@@ -1620,6 +1624,7 @@ template <int Arg> class syclcompat_kernel_scalar;
 
 namespace syclcompat {
 enum error_code { success = 0, backend_error = 1, default_error = 999 };
+inline const char *get_error_string_dummy(int ec);
 }
 
 #define SYCLCOMPAT_CHECK_ERROR(expr)

sycl/include/syclcompat/defs.hpp

@@ -68,7 +68,15 @@ template <int Arg> class syclcompat_kernel_scalar;
 
 namespace syclcompat {
 enum error_code { success = 0, backend_error = 1, default_error = 999 };
+/// A dummy function introduced to assist auto migration.
+/// The SYCLomatic user should replace it with a real error-handling function.
+/// SYCL reports errors using exceptions and does not use error codes.
+inline const char *get_error_string_dummy(int ec) {
+  (void)ec;
+  return "<FIXME: Placeholder>"; // Return the error string for the error code
+                                 // ec.
 }
+} // namespace syclcompat
 
 #define SYCLCOMPAT_CHECK_ERROR(expr)                                           \
   [&]() {                                                                      \