[flang-commits] [flang] [flang][runtime] Fix trailing blanks for Gw.dEe output editing (PR #75263)

[Peter Klausler via flang-commits]

https://github.com/klausler created https://github.com/llvm/llvm-project/pull/75263

When generalized numeric output editing of real data maps to Fw.d output editing, either two or four trailing blanks are emitted depending on the presence and value of 'e'.  The code that detects field width overflow didn't take these trailing blanks into account, and sometimes the field width adjustment was producing an F0.d output edit descriptor (no fixed field width).  Fix by retaining the original field width, but requiring it to also accommodate the trailing blanks.

Fixes llvm-test-suite/Fortran/gfortran/regression/fmt_g.f.

>From 3fa9c7cba3d9e6354b7e5262e4c2bff9ca15ea74 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Tue, 12 Dec 2023 16:22:28 -0800
Subject: [PATCH] [flang][runtime] Fix trailing blanks for Gw.dEe output
 editing

When generalized numeric output editing of real data maps to
Fw.d output editing, either two or four trailing blanks are
emitted depending on the presence and value of 'e'.  The code
that detects field width overflow didn't take these trailing
blanks into account, and sometimes the field width adjustment
was producing an F0.d output edit descriptor (no fixed field
width).  Fix by retaining the original field width, but requiring
it to also accommodate the trailing blanks.

Fixes llvm-test-suite/Fortran/gfortran/regression/fmt_g.f.
---
 flang/runtime/edit-output.cpp | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/flang/runtime/edit-output.cpp b/flang/runtime/edit-output.cpp
index a4ce0b12f91111..a2f0893cd77435 100644
--- a/flang/runtime/edit-output.cpp
+++ b/flang/runtime/edit-output.cpp
@@ -341,11 +341,12 @@ bool RealOutputEditing<KIND>::EditEorDOutput(const DataEdit &edit) {
         ConvertToDecimal(significantDigits, edit.modes.round, flags)};
     if (IsInfOrNaN(converted.str, static_cast<int>(converted.length))) {
       return editWidth > 0 &&
-              converted.length > static_cast<std::size_t>(editWidth)
+              converted.length + trailingBlanks_ >
+                  static_cast<std::size_t>(editWidth)
           ? EmitRepeated(io_, '*', editWidth)
           : EmitPrefix(edit, converted.length, editWidth) &&
               EmitAscii(io_, converted.str, converted.length) &&
-              EmitSuffix(edit);
+              EmitRepeated(io_, ' ', trailingBlanks_) && EmitSuffix(edit);
     }
     if (!IsZero()) {
       converted.decimalExponent -= scale;
@@ -522,8 +523,9 @@ bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
       zeroesBeforePoint = 1; // "." -> "0."
     }
     int totalLength{signLength + digitsBeforePoint + zeroesBeforePoint +
-        1 /*'.'*/ + zeroesAfterPoint + digitsAfterPoint + trailingZeroes};
-    int width{editWidth > 0 ? editWidth : totalLength};
+        1 /*'.'*/ + zeroesAfterPoint + digitsAfterPoint + trailingZeroes +
+        trailingBlanks_ /* G editing converted to F */};
+    int width{editWidth > 0 || trailingBlanks_ ? editWidth : totalLength};
     if (totalLength > width) {
       return EmitRepeated(io_, '*', width);
     }
@@ -574,8 +576,11 @@ DataEdit RealOutputEditing<KIND>::EditForGOutput(DataEdit edit) {
   trailingBlanks_ = 0;
   if (editWidth > 0) {
     int expoDigits{edit.expoDigits.value_or(0)};
+    // F'2023 13.7.5.2.3 p5: "If 0 <= s <= d, the scale factor has no effect
+    // and F(w − n).(d − s),n(’b’) editing is used where b is a blank and
+    // n is 4 for Gw.d editing, e + 2 for Gw.dEe editing if e > 0, and
+    // 4 for Gw.dE0 editing."
     trailingBlanks_ = expoDigits > 0 ? expoDigits + 2 : 4; // 'n'
-    *edit.width = std::max(0, editWidth - trailingBlanks_);
   }
   if (edit.digits.has_value()) {
     *edit.digits = std::max(0, *edit.digits - expo);