1 files changed, 32 insertions, 1 deletions
diff --git a/flang/lib/Semantics/check-allocate.cpp b/flang/lib/Semantics/check-allocate.cpp
index e019bbd..a411e20 100644
--- a/flang/lib/Semantics/check-allocate.cpp
+++ b/flang/lib/Semantics/check-allocate.cpp
@@ -26,6 +26,10 @@ struct AllocateCheckerInfo {
   std::optional<evaluate::DynamicType> sourceExprType;
   std::optional<parser::CharBlock> sourceExprLoc;
   std::optional<parser::CharBlock> typeSpecLoc;
+  std::optional<parser::CharBlock> statSource;
+  std::optional<parser::CharBlock> msgSource;
+  const SomeExpr *statVar{nullptr};
+  const SomeExpr *msgVar{nullptr};
   int sourceExprRank{0}; // only valid if gotMold || gotSource
   bool gotStat{false};
   bool gotMsg{false};
@@ -141,12 +145,15 @@ static std::optional<AllocateCheckerInfo> CheckAllocateOptions(
             [&](const parser::StatOrErrmsg &statOrErr) {
               common::visit(
                   common::visitors{
-                      [&](const parser::StatVariable &) {
+                      [&](const parser::StatVariable &var) {
                         if (info.gotStat) { // C943
                           context.Say(
                               "STAT may not be duplicated in a ALLOCATE statement"_err_en_US);
                         }
                         info.gotStat = true;
+                        info.statVar = GetExpr(context, var);
+                        info.statSource =
+                            parser::Unwrap<parser::Variable>(var)->GetSource();
                       },
                       [&](const parser::MsgVariable &var) {
                         WarnOnDeferredLengthCharacterScalar(context,
@@ -159,6 +166,9 @@ static std::optional<AllocateCheckerInfo> CheckAllocateOptions(
                               "ERRMSG may not be duplicated in a ALLOCATE statement"_err_en_US);
                         }
                         info.gotMsg = true;
+                        info.msgVar = GetExpr(context, var);
+                        info.msgSource =
+                            parser::Unwrap<parser::Variable>(var)->GetSource();
                       },
                   },
                   statOrErr.u);
@@ -460,6 +470,16 @@ static bool HaveCompatibleLengths(
   }
 }
 
+bool AreSameAllocation(const SomeExpr *root, const SomeExpr *path) {
+  if (root && path) {
+    // For now we just use equality of expressions. If we implement a more
+    // sophisticated alias analysis we should use it here.
+    return *root == *path;
+  } else {
+    return false;
+  }
+}
+
 bool AllocationCheckerHelper::RunChecks(SemanticsContext &context) {
   if (!ultimate_) {
     CHECK(context.AnyFatalError());
@@ -690,6 +710,17 @@ bool AllocationCheckerHelper::RunChecks(SemanticsContext &context) {
           "Object in ALLOCATE must have DEVICE attribute when STREAM option is specified"_err_en_US);
     }
   }
+
+  if (const SomeExpr *allocObj{GetExpr(context, allocateObject_)}) {
+    if (AreSameAllocation(allocObj, allocateInfo_.statVar)) {
+      context.Say(allocateInfo_.statSource.value_or(name_.source),
+          "STAT variable in ALLOCATE must not be the variable being allocated"_err_en_US);
+    }
+    if (AreSameAllocation(allocObj, allocateInfo_.msgVar)) {
+      context.Say(allocateInfo_.msgSource.value_or(name_.source),
+          "ERRMSG variable in ALLOCATE must not be the variable being allocated"_err_en_US);
+    }
+  }
   return RunCoarrayRelatedChecks(context);
 }