[llvm] [flang][runtime] Fix formatted input of NAN(...) (PR #149606)

[Peter Klausler via llvm-commits]

https://github.com/klausler updated https://github.com/llvm/llvm-project/pull/149606

>From 676f87f0fb77b4b8325ca4fc1038a4fcde649731 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Fri, 18 Jul 2025 15:34:57 -0700
Subject: [PATCH] [flang][runtime] Fix formatted input of NAN(...)

Formatted real input is allowed to have parenthesized information
after "NAN".  We don't interpret the contents, but we should at
least scan the information correctly.

Fixes https://github.com/llvm/llvm-project/issues/149533.
---
 flang-rt/lib/runtime/edit-input.cpp           | 44 +++++++++++++------
 .../unittests/Runtime/NumericalFormatTest.cpp |  1 +
 2 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/flang-rt/lib/runtime/edit-input.cpp b/flang-rt/lib/runtime/edit-input.cpp
index 13557678f6057..50cbce1fd9049 100644
--- a/flang-rt/lib/runtime/edit-input.cpp
+++ b/flang-rt/lib/runtime/edit-input.cpp
@@ -375,21 +375,37 @@ static RT_API_ATTRS ScannedRealInput ScanRealInput(
         Put(*next);
       }
     }
-    if (next && *next == '(') { // NaN(...)
-      Put('(');
-      int depth{1};
-      while (true) {
-        next = io.NextInField(remaining, edit);
-        if (depth == 0) {
-          break;
-        } else if (!next) {
-          return {}; // error
-        } else if (*next == '(') {
-          ++depth;
-        } else if (*next == ')') {
-          --depth;
+    if (first == 'N' && (!next || *next == '(') &&
+        remaining.value_or(1) > 0) { // NaN(...)?
+      std::size_t byteCount{0};
+      if (!next) { // NextInField won't return '(' for list-directed
+        next = io.GetCurrentChar(byteCount);
+      }
+      if (next && *next == '(') {
+        int depth{1};
+        while (true) {
+          if (*next >= 'a' && *next <= 'z') {
+            *next = *next - 'a' + 'A';
+          }
+          Put(*next);
+          io.HandleRelativePosition(byteCount);
+          io.GotChar(byteCount);
+          if (remaining) {
+            *remaining -= byteCount;
+          }
+          if (depth == 0) {
+            break; // done
+          }
+          next = io.GetCurrentChar(byteCount);
+          if (!next || remaining.value_or(1) < 1) {
+            return {}; // error
+          } else if (*next == '(') {
+            ++depth;
+          } else if (*next == ')') {
+            --depth;
+          }
         }
-        Put(*next);
+        next = io.NextInField(remaining, edit);
       }
     }
   } else if (first == radixPointChar || (first >= '0' && first <= '9') ||
diff --git a/flang-rt/unittests/Runtime/NumericalFormatTest.cpp b/flang-rt/unittests/Runtime/NumericalFormatTest.cpp
index 73245dca13bc0..c69a799f7f242 100644
--- a/flang-rt/unittests/Runtime/NumericalFormatTest.cpp
+++ b/flang-rt/unittests/Runtime/NumericalFormatTest.cpp
@@ -964,6 +964,7 @@ TEST(IOApiTests, EditDoubleInputValues) {
       {"(RU,E9.1)", " 1.0E-325", 0x1, 0},
       {"(E9.1)", "-1.0E-325", 0x8000000000000000, 0},
       {"(RD,E9.1)", "-1.0E-325", 0x8000000000000001, 0},
+      {"(F7.0))", "+NaN(q)", 0x7ff8000000000000, 0},
   };
   for (auto const &[format, data, want, iostat] : testCases) {
     auto cookie{IONAME(BeginInternalFormattedInput)(