[gcc r13-7711] libstdc++: Handle invalid values in std::chrono pretty printers

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:5993775fa3a4a1c87d7dd67ae8f77a98cc4ff91e

commit r13-7711-g5993775fa3a4a1c87d7dd67ae8f77a98cc4ff91e
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Aug 11 12:27:58 2023 +0100

    libstdc++: Handle invalid values in std::chrono pretty printers
    
    This avoids an IndexError exception when printing invalid chrono::month
    or chrono::weekday values.
    
    libstdc++-v3/ChangeLog:
    
            * python/libstdcxx/v6/printers.py (StdChronoCalendarPrinter):
            Check for out-of-range month an weekday indices.
            * testsuite/libstdc++-prettyprinters/chrono.cc: Check invalid
            month and weekday values.
    
    (cherry picked from commit c19b542a177b7b65b013e535ae9f384352808d11)

Diff:
---
 libstdc++-v3/python/libstdcxx/v6/printers.py              | 7 ++++++-
 libstdc++-v3/testsuite/libstdc++-prettyprinters/chrono.cc | 7 +++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py b/libstdc++-v3/python/libstdcxx/v6/printers.py
index b4c427d487cd..0187c4b60e63 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
@@ -2021,11 +2021,16 @@ class StdChronoCalendarPrinter:
         if typ == 'std::chrono::day':
             return '{}'.format(int(val['_M_d']))
         if typ == 'std::chrono::month':
+            if m < 1 or m >= len(months):
+                return "%d is not a valid month" % m
             return months[m]
         if typ == 'std::chrono::year':
             return '{}y'.format(y)
         if typ == 'std::chrono::weekday':
-            return '{}'.format(weekdays[val['_M_wd']])
+            wd = val['_M_wd']
+            if wd < 0 or wd >= len(weekdays):
+                return "%d is not a valid weekday" % wd
+            return '{}'.format(weekdays[wd])
         if typ == 'std::chrono::weekday_indexed':
             return '{}[{}]'.format(val['_M_wd'], int(val['_M_index']))
         if typ == 'std::chrono::weekday_last':
diff --git a/libstdc++-v3/testsuite/libstdc++-prettyprinters/chrono.cc b/libstdc++-v3/testsuite/libstdc++-prettyprinters/chrono.cc
index b5314e025cce..9aa284aea2f3 100644
--- a/libstdc++-v3/testsuite/libstdc++-prettyprinters/chrono.cc
+++ b/libstdc++-v3/testsuite/libstdc++-prettyprinters/chrono.cc
@@ -75,6 +75,13 @@ main()
   [[maybe_unused]] year_month_weekday_last donnerstag = 2017y/July/Thursday[last];
   // { dg-final { note-test donnerstag {2017y/July/Thursday[last]} } }
 
+  [[maybe_unused]] month nam(13);
+  // { dg-final { note-test nam {13 is not a valid month} } }
+  [[maybe_unused]] month nam0(0);
+  // { dg-final { note-test nam0 {0 is not a valid month} } }
+  [[maybe_unused]] weekday nawd(8);
+  // { dg-final { note-test nawd {8 is not a valid weekday} } }
+  //
   hh_mm_ss<seconds> hms(4h + 3min + 2s);
   // { dg-final { note-test hms {04:03:02} } }