Rely on compiler to zero out structs.

Before, we were relying on having contiguous structs and remembering
to manually zero-out fields. Alleviate all concerns by using C99
designator initializers. These are technically not slated to be added
to the C++ standard until C++20. However, because they are in C99, and
they are awesome, they are commonly used in Android.

Bug: 130161842
Test: manual
Change-Id: I96e4bea47f99e00ef33cfce74621e5869b1ff3d7
Merged-In: I96e4bea47f99e00ef33cfce74621e5869b1ff3d7
(cherry picked from commit 16786a76b2c736791f2c364a1bce7632e112e93e)

Parcel.cpp

diff --git a/Parcel.cpp b/Parcel.cpp
index 2b1bb90..6e9bd1e 100644
--- a/Parcel.cpp
+++ b/Parcel.cpp
@@ -196,7 +196,7 @@
 status_t flatten_binder(const sp<ProcessState>& /*proc*/,
     const sp<IBinder>& binder, Parcel* out)
 {
-    flat_binder_object obj;
+    flat_binder_object obj = {};
 
     if (binder != NULL) {
         BHwBinder *local = binder->localBinder();
@@ -238,7 +238,7 @@
 status_t flatten_binder(const sp<ProcessState>& /*proc*/,
     const wp<IBinder>& binder, Parcel* out)
 {
-    flat_binder_object obj;
+    flat_binder_object obj = {};
 
     obj.flags = 0x7f | FLAT_BINDER_FLAG_ACCEPTS_FDS;
     if (binder != NULL) {
@@ -842,15 +842,16 @@
     LOG_BUFFER("writeEmbeddedBuffer(%p, %zu, parent = (%zu, %zu)) -> %zu",
         buffer, length, parent_buffer_handle,
          parent_offset, mObjectsSize);
-    binder_buffer_object obj;
-    obj.hdr.type = BINDER_TYPE_PTR;
-    obj.buffer = reinterpret_cast<binder_uintptr_t>(buffer);
-    obj.length = length;
-    obj.flags = BINDER_BUFFER_FLAG_HAS_PARENT;
     if(!validateBufferParent(parent_buffer_handle, parent_offset))
         return BAD_VALUE;
-    obj.parent = parent_buffer_handle;
-    obj.parent_offset = parent_offset;
+    binder_buffer_object obj = {
+        .hdr = { .type = BINDER_TYPE_PTR },
+        .buffer = reinterpret_cast<binder_uintptr_t>(buffer),
+        .length = length,
+        .flags = BINDER_BUFFER_FLAG_HAS_PARENT,
+        .parent = parent_buffer_handle,
+        .parent_offset = parent_offset,
+    };
     if (handle != nullptr) {
         // We use an index into mObjects as a handle
         *handle = mObjectsSize;
@@ -862,11 +863,12 @@
 {
     LOG_BUFFER("writeBuffer(%p, %zu) -> %zu",
         buffer, length, mObjectsSize);
-    binder_buffer_object obj;
-    obj.hdr.type = BINDER_TYPE_PTR;
-    obj.buffer = reinterpret_cast<binder_uintptr_t>(buffer);
-    obj.length = length;
-    obj.flags = 0;
+    binder_buffer_object obj {
+        .hdr = { .type = BINDER_TYPE_PTR },
+        .buffer = reinterpret_cast<binder_uintptr_t>(buffer),
+        .length = length,
+        .flags = 0,
+    };
     if (handle != nullptr) {
         // We use an index into mObjects as a handle
         *handle = mObjectsSize;
@@ -888,15 +890,16 @@
     status_t status = incrementNumReferences();
     if (status != OK)
         return status;
-    binder_buffer_object obj;
-    obj.hdr.type = BINDER_TYPE_PTR;
-    obj.flags = BINDER_BUFFER_FLAG_REF;
     if (!validateBufferChild(child_buffer_handle, child_offset))
         return BAD_VALUE;
-    // The current binder.h does not have child and child_offset names yet.
-    // Use the buffer and length parameters.
-    obj.buffer = child_buffer_handle;
-    obj.length = child_offset;
+    binder_buffer_object obj {
+        .hdr = { .type = BINDER_TYPE_PTR },
+        .flags = BINDER_BUFFER_FLAG_REF,
+        // The current binder.h does not have child and child_offset names yet.
+        // Use the buffer and length parameters.
+        .buffer = child_buffer_handle,
+        .length = child_offset,
+    };
     if (handle != nullptr)
         // We use an index into mObjects as a handle
         *handle = mObjectsSize;
@@ -915,19 +918,20 @@
     status_t status = incrementNumReferences();
     if (status != OK)
         return status;
-    binder_buffer_object obj;
-    obj.hdr.type = BINDER_TYPE_PTR;
-    obj.flags = BINDER_BUFFER_FLAG_REF | BINDER_BUFFER_FLAG_HAS_PARENT;
-    if (!validateBufferChild(child_buffer_handle, child_offset))
-        return BAD_VALUE;
     // The current binder.h does not have child and child_offset names yet.
     // Use the buffer and length parameters.
-    obj.buffer = child_buffer_handle;
-    obj.length = child_offset;
+    if (!validateBufferChild(child_buffer_handle, child_offset))
+        return BAD_VALUE;
     if(!validateBufferParent(parent_buffer_handle, parent_offset))
         return BAD_VALUE;
-    obj.parent = parent_buffer_handle;
-    obj.parent_offset = parent_offset;
+    binder_buffer_object obj {
+        .hdr = { .type = BINDER_TYPE_PTR },
+        .flags = BINDER_BUFFER_FLAG_REF | BINDER_BUFFER_FLAG_HAS_PARENT,
+        .buffer = child_buffer_handle,
+        .length = child_offset,
+        .parent = parent_buffer_handle,
+        .parent_offset = parent_offset,
+    };
     if (handle != nullptr) {
         // We use an index into mObjects as a handle
         *handle = mObjectsSize;
@@ -940,9 +944,12 @@
     status_t status = incrementNumReferences();
     if (status != OK)
         return status;
-    binder_buffer_object obj;
-    obj.hdr.type = BINDER_TYPE_PTR;
-    obj.flags = BINDER_BUFFER_FLAG_REF;
+
+    binder_buffer_object obj {
+        .hdr = { .type = BINDER_TYPE_PTR },
+        .flags = BINDER_BUFFER_FLAG_REF,
+    };
+
     if (handle != nullptr)
         // We use an index into mObjects as a handle
         *handle = mObjectsSize;
@@ -958,14 +965,14 @@
     status_t status = incrementNumReferences();
     if (status != OK)
         return status;
-    binder_buffer_object obj;
-    obj.hdr.type = BINDER_TYPE_PTR;
-    obj.flags = BINDER_BUFFER_FLAG_REF | BINDER_BUFFER_FLAG_HAS_PARENT;
-    // parent_buffer_handle and parent_offset needs to be checked.
     if(!validateBufferParent(parent_buffer_handle, parent_offset))
         return BAD_VALUE;
-    obj.parent = parent_buffer_handle;
-    obj.parent_offset = parent_offset;
+    binder_buffer_object obj {
+        .hdr = { .type = BINDER_TYPE_PTR, },
+        .flags = BINDER_BUFFER_FLAG_REF | BINDER_BUFFER_FLAG_HAS_PARENT,
+        .parent = parent_buffer_handle,
+        .parent_offset = parent_offset,
+    };
     if (handle != nullptr) {
         // We use an index into mObjects as a handle
         *handle = mObjectsSize;
@@ -1050,7 +1057,6 @@
                                         size_t parent_buffer_handle,
                                         size_t parent_offset)
 {
-    struct binder_fd_array_object fd_array;
     size_t buffer_handle;
     status_t status = OK;
 
@@ -1075,10 +1081,12 @@
         return status;
     }
 
-    fd_array.hdr.type = BINDER_TYPE_FDA;
-    fd_array.num_fds = handle->numFds;
-    fd_array.parent = buffer_handle;
-    fd_array.parent_offset = offsetof(native_handle_t, data);
+    struct binder_fd_array_object fd_array {
+        .hdr = { .type = BINDER_TYPE_FDA },
+        .num_fds = static_cast<binder_size_t>(handle->numFds),
+        .parent = buffer_handle,
+        .parent_offset = offsetof(native_handle_t, data),
+    };
 
     return writeObject(fd_array);
 }