[flang-commits] [PATCH] D152295: [flang] Set "undefined" NEXTREC=n variable to 0 rather than random garbage

[Peter Klausler via Phabricator via flang-commits]

klausler created this revision.
klausler added a reviewer: tarunprabhu.
klausler added a project: Flang.
Herald added subscribers: sunshaoce, jdoerfert.
Herald added a project: All.
klausler requested review of this revision.

12.10.2.17 defines that a INQUIRE statement's NEXTREC=n output value 
for a unit that is not connected for direct access becomes undefined,
but the current I/O runtime can fail in a confusing manner by trying
to return uninitialized stack garbage.

Reported on Slack by Tarun Prabhu as an intermittent failure in
the gfortran regression test inquire_pre.f90.


https://reviews.llvm.org/D152295

Files:
  flang/runtime/io-api.cpp


Index: flang/runtime/io-api.cpp
===================================================================
--- flang/runtime/io-api.cpp
+++ flang/runtime/io-api.cpp
@@ -1451,15 +1451,14 @@
 bool IONAME(InquireInteger64)(
     Cookie cookie, InquiryKeywordHash inquiry, std::int64_t &result, int kind) {
   IoStatementState &io{*cookie};
-  std::int64_t n;
+  std::int64_t n{0}; // safe "undefined" value
   if (io.Inquire(inquiry, n)) {
     if (SetInteger(result, kind, n)) {
       return true;
     }
     io.GetIoErrorHandler().SignalError(
         "InquireInteger64(): bad INTEGER kind(%d) or out-of-range "
-        "value(%jd) "
-        "for result",
+        "value(%jd) for result",
         kind, static_cast<std::intmax_t>(n));
   }
   return false;


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