Re: QString and ctype(3)

[Paul Ripke <stix%stix.id.au@localhost>]

On Tue, Jul 01, 2025 at 06:11:25PM -0400, Greg Troxel wrote:
> The qgis build crashes on NetBSD current with:
> 
>   FAILED: src/crssync/CMakeFiles/synccrsdb /n0/tmp/work/geography/qgis/work/qgis-3.40.7/cmake-pkgsrc-build/src/crssync/CMakeFiles/synccrsdb 
>   cd /n0/tmp/work/geography/qgis/work/qgis-3.40.7/cmake-pkgsrc-build/src/crssync && env LD_LIBRARY_PATH=/n0/tmp/work/geography/qgis/work/qgis-3.40.7/cmake-pkgsrc-build/output/bin/../lib DYLD_LIBRARY_PATH=/n0/tmp/work/geography/qgis/work/qgis-3.40.7/cmake-pkgsrc-build/output/bin/../lib /n0/tmp/work/geography/qgis/work/qgis-3.40.7/cmake-pkgsrc-build/output/bin/crssync
>   ctype(3) tolower: invalid input: -62
>   ninja: build stopped: subcommand failed.
> 
> and I think it's because of
> 
>   bool QgsCoordinateReferenceSystem::createFromString( const QString &definition )
>   {
>     if ( definition.isEmpty() )
>       return false;
> 
>     QgsReadWriteLocker locker( *sCrsStringLock(), QgsReadWriteLocker::Read );
>     if ( !sDisableStringCache )
>     {
>       QHash< QString, QgsCoordinateReferenceSystem >::const_iterator crsIt = sStringCache()->constFind( definition );
>       if ( crsIt != sStringCache()->constEnd() )
>       {
>         // found a match in the cache                                                                                                                                                                                                                                                        
>         *this = crsIt.value();
>         return d->mIsValid;
>       }
>     }
>     locker.unlock();
> 
>     bool result = false;
>     const thread_local QRegularExpression reCrsId( QStringLiteral( "^(epsg|esri|osgeo|ignf|ogc|nkg|zangi|iau_2015|iau2000|postgis|internal|user)\\:(\\w+)$" ), QRegularExpression::CaseInsensitiveOption );
>     QRegularExpressionMatch match = reCrsId.match( definition );
>     if ( match.capturedStart() == 0 )
>     {
>       QString authName = match.captured( 1 ).toLower();
>       if ( authName == QLatin1String( "epsg" ) )
>       {
>         result = createFromOgcWmsCrs( definition );
>       }
> 
> Perhaps, because a QString is char, not unsigned char -- but that's
> guessing.  But it may be some other toLower, not the one above.
> 
> cppreference.com (not sure I should believe that) says .toLower is a
> horror show:
> 
>   https://en.cppreference.com/w/cpp/string/byte/tolower
> 
> 
> 
> Is anyone else seeing issues with QT programs under NetBSD current?

Reading thru qt6 source, QUnicodeTables::convertCase() doesn't seem to
rely on ctype(3). Sure it's not one of the usages in qgis itself? They
look suspect, I think? I don't have a system running current to easily
test.

fwiw, I've tripped over ctype(3) breakage previously, too, most recently:
https://github.com/stixpjr/widelands/commit/755251e0d89d7b739645d1cafbf3351ae1ca74b8

The fact the ctype(3) API takes (int) args but has UB if called with
a value <-1 is just asking for trouble.

Cheers,
-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.