commit 92f85fb5e86b6f3dcf95487a4c2b3c9eda680994
author Peter Klausler <pklausler@nvidia.com> Tue Jun 06 11:37:52 2023 -0700
committer Copybara-Service <copybara-worker@google.com> Tue Jun 06 12:00:51 2023 -0700
tree d4394f3dadbe49c9adb549fef7a47f78387df2fc
parent 68bf3d8cca30d5c8729bf1078cfdf4f9b1b04191

[flang] Set "undefined" NEXTREC=n variable to 0 rather than random garbage

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.

Differential Revision: https://reviews.llvm.org/D152295

GitOrigin-RevId: e468f07550c56eeb49659d02c7c5c3f79f53db6f

runtime/io-api.cpp

diff --git a/runtime/io-api.cpp b/runtime/io-api.cpp
index 09639c1..4d569f8 100644
--- a/runtime/io-api.cpp
+++ b/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;