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, 2 insertions, 1 deletions

diff --git a/tools/source/xml/XmlWalker.cxx b/tools/source/xml/XmlWalker.cxx
index b21c22335018..219bf10c8bb5 100644
--- a/tools/source/xml/XmlWalker.cxx
+++ b/tools/source/xml/XmlWalker.cxx
@@ -90,7 +90,8 @@ OString XmlWalker::attribute(const OString& sName)
 {
     xmlChar* xmlName = xmlCharStrdup(sName.getStr());
     xmlChar* xmlAttribute = xmlGetProp(mpImpl->mpCurrent, xmlName);
-    OString aAttributeContent(reinterpret_cast<const char*>(xmlAttribute));
+    OString aAttributeContent(
+        xmlAttribute == nullptr ? "" : reinterpret_cast<const char*>(xmlAttribute));
     xmlFree(xmlAttribute);
     xmlFree(xmlName);