From cfb77ef1a79ad9fd8b84e491910260d440e09ea5 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Tue, 24 Jun 2025 16:02:59 -0700
Subject: [PATCH] `<xloctime>`: Silence CodeQL warning SM03231 about leap year
 arithmetic

This is cpp/microsoft/public/leap-year/unchecked-after-arithmetic-year-modification,
"Year field changed using an arithmetic operation without checking for leap year".

Only the line with the conditional operator appeared to be emitting this warning,
but to be safe I'm restructuring the code to use if-statements consistently
(the comments make it clearer anyways), and to suppress the CodeQL warning whenever we're performing arithmetic.
---
 stl/inc/xloctime | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/stl/inc/xloctime b/stl/inc/xloctime
index 65de12ff9c8..1c3f96a5e34 100644
--- a/stl/inc/xloctime
+++ b/stl/inc/xloctime
@@ -418,11 +418,13 @@ protected:
         if (!(_Res & ios_base::failbit)) {
             if (_Digits_read <= 2) {
                 if (_Ans < 69) {
+                    // CodeQL [SM03231] This is parsing tm_year (years since 1900); leap years are irrelevant.
                     _Pt->tm_year = _Ans + 100; // [00, 68] parsed as [2000, 2068]
                 } else if (_Ans < 100) {
                     _Pt->tm_year = _Ans; // [69, 99] parsed as [1969, 1999]
                 }
             } else {
+                // CodeQL [SM03231] This is parsing tm_year (years since 1900); leap years are irrelevant.
                 _Pt->tm_year = _Ans - 1900; // parsed literally
             }
         }
@@ -456,6 +458,7 @@ protected:
         case 'C':
             _State |= _Getint(_First, _Last, 0, 99, _Ans, _Ctype_fac);
             if (!(_State & ios_base::failbit)) {
+                // CodeQL [SM03231] This is parsing tm_year (years since 1900); leap years are irrelevant.
                 _Pt->tm_year = _Ans * 100 - 1900; // convert to century
             }
 
@@ -549,7 +552,12 @@ protected:
         case 'y':
             _State |= _Getint(_First, _Last, 0, 99, _Ans, _Ctype_fac);
             if (!(_State & ios_base::failbit)) {
-                _Pt->tm_year = _Ans < 69 ? _Ans + 100 : _Ans;
+                if (_Ans < 69) {
+                    // CodeQL [SM03231] This is parsing tm_year (years since 1900); leap years are irrelevant.
+                    _Pt->tm_year = _Ans + 100; // [00, 68] parsed as [2000, 2068]
+                } else {
+                    _Pt->tm_year = _Ans; // [69, 99] parsed as [1969, 1999]
+                }
             }
 
             break;
@@ -557,7 +565,8 @@ protected:
         case 'Y':
             _State |= _Getint(_First, _Last, 0, 9999, _Ans, _Ctype_fac);
             if (!(_State & ios_base::failbit)) {
-                _Pt->tm_year = _Ans - 1900;
+                // CodeQL [SM03231] This is parsing tm_year (years since 1900); leap years are irrelevant.
+                _Pt->tm_year = _Ans - 1900; // parsed literally
             }
             break;