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io: Correct handling of byte count pos in TBufferFile::ReadObjectAny #21192

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io: Correct handling of byte count pos in TBufferFile::ReadObjectAny #21192

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13 changes: 7 additions & 6 deletions io/io/src/TBufferFile.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -2593,7 +2593,8 @@ void *TBufferFile::ReadObjectAny(const TClass *clCast)
InitMap();

// before reading object save start position
UInt_t startpos = UInt_t(fBufCur-fBuffer);
ULong64_t startpos = static_cast<ULong64_t>(fBufCur-fBuffer);
ULong64_t cntpos = startpos <= kMaxCountPosition ? startpos : kOverflowPosition;
Comment on lines +2596 to +2597
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@jblomer jblomer Feb 9, 2026

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Don't we need to push the startpos on the stack if it's large?


// attempt to load next object as TClass clCast
UInt_t tag; // either tag or byte count
Expand All @@ -2613,7 +2614,7 @@ void *TBufferFile::ReadObjectAny(const TClass *clCast)
Error("ReadObject", "got object of wrong class! requested %s but got %s",
clCast->GetName(), clRef->GetName());

CheckByteCount(startpos, tag, (TClass *)nullptr); // avoid mis-leading byte count error message
CheckByteCount(cntpos, tag, (TClass *)nullptr); // avoid mis-leading byte count error message
return 0; // We better return at this point
}
baseOffset = 0; // For now we do not support requesting from a class that is the base of one of the class for which there is transformation to ....
Expand All @@ -2628,7 +2629,7 @@ void *TBufferFile::ReadObjectAny(const TClass *clCast)
//we cannot mix a compiled class with an emulated class in the inheritance
Error("ReadObject", "trying to read an emulated class (%s) to store in a compiled pointer (%s)",
clRef->GetName(),clCast->GetName());
CheckByteCount(startpos, tag, (TClass *)nullptr); // avoid mis-leading byte count error message
CheckByteCount(cntpos, tag, (TClass *)nullptr); // avoid mis-leading byte count error message
return 0;
}
}
Expand All @@ -2640,7 +2641,7 @@ void *TBufferFile::ReadObjectAny(const TClass *clCast)
obj = (char *) (Longptr_t)fMap->GetValue(startpos+kMapOffset);
if (obj == (void*) -1) obj = nullptr;
if (obj) {
CheckByteCount(startpos, tag, (TClass *)nullptr);
CheckByteCount(cntpos, tag, (TClass *)nullptr);
return (obj + baseOffset);
}
}
Expand All @@ -2652,7 +2653,7 @@ void *TBufferFile::ReadObjectAny(const TClass *clCast)
MapObject((TObject*) -1, startpos+kMapOffset);
else
MapObject((void*)nullptr, nullptr, fMapCount);
CheckByteCount(startpos, tag, (TClass *)nullptr);
CheckByteCount(cntpos, tag, (TClass *)nullptr);
return 0;
}

Expand Down Expand Up @@ -2711,7 +2712,7 @@ void *TBufferFile::ReadObjectAny(const TClass *clCast)
// let the object read itself
clRef->Streamer( obj, *this, clOnfile );

CheckByteCount(startpos, tag, clRef);
CheckByteCount(cntpos, tag, clRef);
}

return obj+baseOffset;
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