[SYCL] Fix Coverity null reference hits, divide by 0 hits (#15247)

This PR fixes many Coverity hits:
- Adds checks ensuring potentially nullable values are not dereferenced
- Adds a sanity check on get_mem_granularity, ensuring memory
granularity can never be 0
- This is done to fix a divide by 0 coverity hit, as the return result
of get_mem_granularity is used directly in division.

Author: ianayl

sycl/source/backend.cpp

@@ -198,6 +198,11 @@ make_kernel_bundle(ur_native_handle_t NativeHandle,
 
   Plugin->call(urProgramCreateWithNativeHandle, NativeHandle,
                ContextImpl->getHandleRef(), &Properties, &UrProgram);
+  if (UrProgram == nullptr)
+    throw sycl::exception(
+        sycl::make_error_code(sycl::errc::invalid),
+        "urProgramCreateWithNativeHandle resulted in a null program handle.");
+
   if (ContextImpl->getBackend() == backend::opencl)
     Plugin->call(urProgramRetain, UrProgram);
 

sycl/source/detail/kernel_bundle_impl.hpp

@@ -455,6 +455,10 @@ class kernel_bundle_impl {
     Plugin->call(urProgramCreateWithIL, ContextImpl->getHandleRef(),
                  spirv.data(), spirv.size(), nullptr, &UrProgram);
     // program created by urProgramCreateWithIL is implicitly retained.
+    if (UrProgram == nullptr)
+      throw sycl::exception(
+          sycl::make_error_code(errc::invalid),
+          "urProgramCreateWithIL resulted in a null program handle.");
 
     std::string XsFlags = extractXsFlags(BuildOptions);
     auto Res =

sycl/source/detail/plugin.hpp

@@ -66,7 +66,8 @@ class plugin {
       ur_result = call_nocheck(urAdapterGetLastError, MAdapter, &message, &adapter_error);
 
       // If the warning level is greater then 2 emit the message
-      if (detail::SYCLConfig<detail::SYCL_RT_WARNING_LEVEL>::get() >= 2) {
+      if (message != nullptr &&
+          detail::SYCLConfig<detail::SYCL_RT_WARNING_LEVEL>::get() >= 2) {
         std::clog << message << std::endl;
       }
 

sycl/source/virtual_mem.cpp

@@ -58,6 +58,10 @@ __SYCL_EXPORT size_t get_mem_granularity(const device &SyclDevice,
   Plugin->call(urVirtualMemGranularityGetInfo, ContextImpl->getHandleRef(),
                DeviceImpl->getHandleRef(), GranularityQuery, sizeof(size_t),
                &Granularity, nullptr);
+  if (Granularity == 0)
+    throw sycl::exception(
+        sycl::make_error_code(sycl::errc::invalid),
+        "Unexpected granularity result: memory granularity shouldn't be 0.");
   return Granularity;
 }