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Commit584beaa

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joyeecheungmarco-ippolito
authored andcommitted
src: zero-initialize data that are copied into the snapshot
To prevent padding from making the snapshot unreproducible,zero-initialize the data that are copied into the snapshotso that the padding copied are all zeros. This is betterthan enlarging the enums to align the fields since it doesn'tmake the snapshot bigger than necessary, and it removes theneed of using static assertions to ensure alignment.PR-URL:#53563Refs:#50983Reviewed-By: Chengzhong Wu <legendecas@gmail.com>Reviewed-By: Tobias Nießen <tniessen@tnie.de>Reviewed-By: Richard Lau <rlau@redhat.com>Reviewed-By: Daniel Lemire <daniel@lemire.me>Reviewed-By: James M Snell <jasnell@gmail.com>
1 parent229f7f8 commit584beaa

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2 files changed

+4
-1
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2 files changed

+4
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‎src/node_snapshotable.cc

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1357,9 +1357,11 @@ StartupData SerializeNodeContextInternalFields(Local<Object> holder,
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// To serialize the type field, save data in a EmbedderTypeInfo.
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if (index == BaseObject::kEmbedderType) {
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int size =sizeof(EmbedderTypeInfo);
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char* data =newchar[size];
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// We need to use placement new because V8 calls delete[] on the returned
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// data.
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// The () syntax at the end would zero-initialize the block and make
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// the padding reproducible.
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char* data =newchar[size]();
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// TODO(joyeecheung): support cppgc objects.
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new (data)EmbedderTypeInfo(obj->type(),
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EmbedderTypeInfo::MemoryMode::kBaseObject);

‎src/node_snapshotable.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -47,6 +47,7 @@ struct InternalFieldInfoBase {
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std::is_same_v<InternalFieldInfoBase, T>,
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"Can only accept InternalFieldInfoBase subclasses");
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void* buf = ::operatornew[](sizeof(T));
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memset(buf,0,sizeof(T));// Make the padding reproducible.
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T* result =new (buf) T;
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result->type = type;
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result->length =sizeof(T);

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