HLE: Revamp error handling throrough the HLE code

All service calls in the CTR OS return result codes indicating the
success or failure of the call. Previous to this commit, Citra's HLE
emulation of services and the kernel universally either ignored errors
or returned dummy -1 error codes.

This commit makes an initial effort to provide an infrastructure for
error reporting and propagation which can be use going forward to make
HLE calls accurately return errors as the original system. A few parts
of the code have been updated to use the new system where applicable.

One part of this effort is the definition of the `ResultCode` type,
which provides facilities for constructing and parsing error codes in
the structured format used by the CTR.

The `ResultVal` type builds on `ResultCode` by providing a container for
values returned by function that can report errors. It enforces that
correct error checking will be done on function returns by preventing
the use of the return value if the function returned an error code.

Currently this change is mostly internal since errors are still
suppressed on the ARM<->HLE border, as a temporary compatibility hack.
As functionality is implemented and tested this hack can be eventually
removed.

1 files changed, 6 insertions, 11 deletions

diff --git a/src/core/hle/service/gsp_gpu.cpp b/src/core/hle/service/gsp_gpu.cpp
index 66daded9..de1bd3f6 100644
--- a/src/core/hle/service/gsp_gpu.cpp
+++ b/src/core/hle/service/gsp_gpu.cpp
@@ -28,28 +28,23 @@ u32 g_thread_id = 1;            ///< Thread index into interrupt relay queue, 1
 
 /// Gets a pointer to a thread command buffer in GSP shared memory
 static inline u8* GetCommandBuffer(u32 thread_id) {
-    if (0 == g_shared_memory)
-        return nullptr;
-
-    return Kernel::GetSharedMemoryPointer(g_shared_memory,
-        0x800 + (thread_id * sizeof(CommandBuffer)));
+    ResultVal<u8*> ptr = Kernel::GetSharedMemoryPointer(g_shared_memory, 0x800 + (thread_id * sizeof(CommandBuffer)));
+    return ptr.ValueOr(nullptr);
 }
 
 static inline FrameBufferUpdate* GetFrameBufferInfo(u32 thread_id, u32 screen_index) {
-    if (0 == g_shared_memory)
-        return nullptr;
-
     _dbg_assert_msg_(GSP, screen_index < 2, "Invalid screen index");
 
     // For each thread there are two FrameBufferUpdate fields
     u32 offset = 0x200 + (2 * thread_id + screen_index) * sizeof(FrameBufferUpdate);
-    return (FrameBufferUpdate*)Kernel::GetSharedMemoryPointer(g_shared_memory, offset);
+    ResultVal<u8*> ptr = Kernel::GetSharedMemoryPointer(g_shared_memory, offset);
+    return reinterpret_cast<FrameBufferUpdate*>(ptr.ValueOr(nullptr));
 }
 
 /// Gets a pointer to the interrupt relay queue for a given thread index
 static inline InterruptRelayQueue* GetInterruptRelayQueue(u32 thread_id) {
-    return (InterruptRelayQueue*)Kernel::GetSharedMemoryPointer(g_shared_memory,
-        sizeof(InterruptRelayQueue) * thread_id);
+    ResultVal<u8*> ptr = Kernel::GetSharedMemoryPointer(g_shared_memory, sizeof(InterruptRelayQueue) * thread_id);
+    return reinterpret_cast<InterruptRelayQueue*>(ptr.ValueOr(nullptr));
 }
 
 static void WriteHWRegs(u32 base_address, u32 size_in_bytes, const u32* data) {