Avoid calling OString ctor with null pointer

...in preparation of potential future changes from using OString to using
std::string_view, where OString has an undocumented feature of allowing
construction from a null pointer.

This is mostly the result of a manual audit of potentially problematic getenv
calls across the code base.  But there can be other problematic places too, like
the xmlGetProp call in tools/source/xml/XmlWalker.cxx.  To identify those,
rtl_{string,uString}_newFromStr aborts now in non-production debug builds when a
null pointer is passed(and all places that hit with a full `make check
screenshot` have been addressed here).  Once we are confident that all
problematic places have been identified, we should drop support for the
undocumented feature (see the TODO in sal/rtl/strtmpl.cxx).

Change-Id: I595cc6d4f1cda74add2a3db171323f817d362b08
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/107430
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/vcl/unx/generic/dtrans/X11_selection.cxx b/vcl/unx/generic/dtrans/X11_selection.cxx
index ce98fcbd09f5..b9b96f9e514d 100644
--- a/vcl/unx/generic/dtrans/X11_selection.cxx
+++ b/vcl/unx/generic/dtrans/X11_selection.cxx
@@ -675,7 +675,9 @@ SelectionManager& SelectionManager::get( const OUString& rDisplayName )
 
     OUString aDisplayName( rDisplayName );
     if( aDisplayName.isEmpty() )
-        aDisplayName = OStringToOUString( getenv( "DISPLAY" ), RTL_TEXTENCODING_ISO_8859_1 );
+        if (auto const env = getenv( "DISPLAY" )) {
+            aDisplayName = OStringToOUString( env, RTL_TEXTENCODING_ISO_8859_1 );
+        }
     SelectionManager* pInstance = nullptr;
 
     std::unordered_map< OUString, SelectionManager* >::iterator it = getInstances().find( aDisplayName );