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, 4 insertions, 1 deletions

diff --git a/vcl/qt5/Qt5Instance_Print.cxx b/vcl/qt5/Qt5Instance_Print.cxx
index 3670eb67e4cd..1052907ba1ac 100644
--- a/vcl/qt5/Qt5Instance_Print.cxx
+++ b/vcl/qt5/Qt5Instance_Print.cxx
@@ -50,7 +50,10 @@ static OUString getPdfDir(const PrinterInfo& rInfo)
             sal_Int32 nPos = 0;
             aDir = aToken.getToken(1, '=', nPos);
             if (aDir.isEmpty())
-                aDir = OStringToOUString(OString(getenv("HOME")), osl_getThreadTextEncoding());
+                if (auto const env = getenv("HOME"))
+                {
+                    aDir = OStringToOUString(OString(env), osl_getThreadTextEncoding());
+                }
             break;
         }
     }