[flang-commits] [PATCH] D127027: [flang] Don't crash on initialization with a zero-sized derived type

[Peter Klausler via Phabricator via flang-commits]

klausler created this revision.
klausler added a reviewer: vdonaldson.
klausler added a project: Flang.
Herald added a subscriber: jdoerfert.
Herald added a project: All.
klausler requested review of this revision.

Avoid calls to memcpy with zero byte counts if their address argument
calculations may not be valid expressions.


https://reviews.llvm.org/D127027

Files:
  flang/include/flang/Evaluate/initial-image.h
  flang/lib/Evaluate/initial-image.cpp


Index: flang/lib/Evaluate/initial-image.cpp
===================================================================
--- flang/lib/Evaluate/initial-image.cpp
+++ flang/lib/Evaluate/initial-image.cpp
@@ -24,8 +24,7 @@
       return SizeMismatch;
     } else {
       auto at{x.lbounds()};
-      for (auto elements{TotalElementCount(x.shape())}; elements-- > 0;
-           x.IncrementSubscripts(at)) {
+      for (; elements-- > 0; x.IncrementSubscripts(at)) {
         auto scalar{x.At(at)};
         // TODO: length type parameter values?
         for (const auto &[symbolRef, indExpr] : scalar) {
@@ -38,7 +37,7 @@
             Result added{Add(offset + component.offset(), component.size(),
                 indExpr.value(), context)};
             if (added != Ok) {
-              return Ok;
+              return added;
             }
           }
         }
Index: flang/include/flang/Evaluate/initial-image.h
===================================================================
--- flang/include/flang/Evaluate/initial-image.h
+++ flang/include/flang/Evaluate/initial-image.h
@@ -49,6 +49,8 @@
           bytes !=
               x.values().size() * static_cast<std::size_t>(*elementBytes)) {
         return SizeMismatch;
+      } else if (bytes == 0) {
+        return Ok;
       } else {
         std::memcpy(&data_.at(offset), &x.values().at(0), bytes);
         return Ok;
@@ -66,6 +68,8 @@
       auto elementBytes{bytes > 0 ? bytes / elements : 0};
       if (elements * elementBytes != bytes) {
         return SizeMismatch;
+      } else if (bytes == 0) {
+        return Ok;
       } else {
         for (auto at{x.lbounds()}; elements-- > 0; x.IncrementSubscripts(at)) {
           auto scalar{x.At(at)}; // this is a std string; size() in chars
@@ -76,7 +80,7 @@
               (scalarBytes > elementBytes && elements != 0)) {
             return SizeMismatch;
           }
-          std::memcpy(&data_[offset], scalar.data(), elementBytes);
+          std::memcpy(&data_.at(offset), scalar.data(), elementBytes);
           offset += elementBytes;
         }
         return Ok;


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