From 4b4ab1430b1f512aa52b65af8d978332423af419 Mon Sep 17 00:00:00 2001
From: Udit Agarwal <16324601+uditagarwal97@users.noreply.github.com>
Date: Mon, 4 Mar 2024 15:17:50 -0800
Subject: [PATCH] [SYCL] Make ONEAPI_DEVICE_SELECTOR reject an empty string
 (#12851)

```ONEAPI_DEVICE_SELECTOR=""``` causes SYCL runtime to silently not select/initialize any device at all. This PR makes SYCL runtime to throw an error when input to ONEAPI_DEVICE_SELECTOR is null.
---
 sycl/source/detail/config.hpp                        | 7 +++++++
 sycl/test-e2e/OneapiDeviceSelector/illegal_input.cpp | 1 +
 sycl/test/basic_tests/device-selectors-exception.cpp | 4 +++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/sycl/source/detail/config.hpp b/sycl/source/detail/config.hpp
index 1fdf229860022..633a8227873ad 100644
--- a/sycl/source/detail/config.hpp
+++ b/sycl/source/detail/config.hpp
@@ -270,6 +270,13 @@ template <> class SYCLConfig<ONEAPI_DEVICE_SELECTOR> {
     }
     const char *ValStr = BaseT::getRawValue();
     if (ValStr) {
+      // Throw if the input string is empty.
+      if (ValStr[0] == '\0')
+        throw invalid_parameter_error(
+            "Invalid value for ONEAPI_DEVICE_SELECTOR environment "
+            "variable: value should not be null.",
+            PI_ERROR_INVALID_VALUE);
+
       DeviceTargets =
           &GlobalHandler::instance().getOneapiDeviceSelectorTargets(ValStr);
     }
diff --git a/sycl/test-e2e/OneapiDeviceSelector/illegal_input.cpp b/sycl/test-e2e/OneapiDeviceSelector/illegal_input.cpp
index 59129cf820abe..e21915ad9b23f 100644
--- a/sycl/test-e2e/OneapiDeviceSelector/illegal_input.cpp
+++ b/sycl/test-e2e/OneapiDeviceSelector/illegal_input.cpp
@@ -9,6 +9,7 @@
 // RUN: env ONEAPI_DEVICE_SELECTOR="level_zero:" %{run-unfiltered-devices} %t.out
 // RUN: env ONEAPI_DEVICE_SELECTOR="level_zero:::gpu" %{run-unfiltered-devices} %t.out
 // RUN: env ONEAPI_DEVICE_SELECTOR="level_zero:.1" %{run-unfiltered-devices} %t.out
+// RUN: env ONEAPI_DEVICE_SELECTOR="" %{run-unfiltered-devices} %t.out
 // XFAIL: *
 
 // Calling ONEAPI_DEVICE_SELECTOR with an illegal input should result in an
diff --git a/sycl/test/basic_tests/device-selectors-exception.cpp b/sycl/test/basic_tests/device-selectors-exception.cpp
index 5bddf0ed43454..2256b7f4745b8 100644
--- a/sycl/test/basic_tests/device-selectors-exception.cpp
+++ b/sycl/test/basic_tests/device-selectors-exception.cpp
@@ -1,7 +1,9 @@
 // RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %s -o %t.out
 // RUN: env SYCL_DEVICE_FILTER="" %t.out
 // RUN: %if preview-breaking-changes-supported %{ %clangxx -fsycl -fsycl-targets=%sycl_triple -fpreview-breaking-changes %s -o %t.out %}
-// RUN: %if preview-breaking-changes-supported %{ env ONEAPI_DEVICE_SELECTOR="" %t.out %}
+// ONEAPI_DEVICE_SELECTOR="*:-1" causes this test to not select any device at
+// all.
+// RUN: %if preview-breaking-changes-supported %{ env ONEAPI_DEVICE_SELECTOR="*:-1" %t.out %}
 
 #include <sycl/sycl.hpp>
 using namespace sycl;