[flang-commits] [flang] [llvm] [flang-rt] Split large unformatted sequential records into subrecords (PR #213003)

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@@ -376,21 +472,28 @@ bool ExternalFileUnit::AdvanceRecord(IoErrorHandler &handler) {
       }
     } else if (*isUnformatted) {
       if (access == Access::Sequential) {
-        // Append the length of a sequential unformatted variable-length record
-        // as its footer, then overwrite the reserved first four bytes of the
-        // record with its length as its header.  These four bytes were skipped
-        // over in BeginUnformattedIO<Output>().
-        // TODO: Break very large records up into subrecords with negative
-        // headers &/or footers
-        std::uint32_t length;
-        length = furthestPositionInRecord - sizeof length;
-        ok = ok &&
-            Emit(reinterpret_cast<const char *>(&length), sizeof length,
-                sizeof length, handler);
-        positionInRecord = 0;
-        ok = ok &&
-            Emit(reinterpret_cast<const char *>(&length), sizeof length,
-                sizeof length, handler);
+        std::size_t payload{
+            static_cast<std::size_t>(furthestPositionInRecord - kRecMarkSize)};
+        if (payload <= static_cast<std::size_t>(kMaxSubrecPayload)) {
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ejose02 wrote:

Done. payload > *openRecl before subrecord layout.

https://github.com/llvm/llvm-project/pull/213003