Relax non-null requirement for some rtl_uString_* functions

...that take a pointer and a length, and where it should be OK that the pointer
is null if the length is zero.  Those rtl_uString_* functions are targets of
OUString member functions that take std::[u16]string_view arguments, and
19926ed35ebb623fc896942b1f232b83edf1fc1e "loplugin:stringview: Flag empty string
converted to string view" (which changed some call sites to pass in default-
constructed std::[u16]string_view, for which data() returns null) revealed that
those rtl_uString_* functions were not prepared for such input.

(The guardings of memcpy are necessary because memcpy still requires its pointer
arguments to be non-null, even if the corresponding length is zero.)

The new sal/qa/rtl/strings/test_strings_defaultstringview.cxx systematically
tests all O[U]String[Buffer] member functions taking std::[u16]string_view
arguments.  It revealed one further issue in
IMPL_RTL_STRNAME(compare_WithLength), where UBSan reported a
nullptr-with-nonzero-offset

> sal/rtl/strtmpl.cxx:149:9: runtime error: applying non-zero offset 18446744073709551614 to null pointer

Also, rtl_uString_newReplaceFirstUtf16LUtf16L was found to lack a check for its
`from` argument to be non-null.

Change-Id: I6a7a712570f7d1e8d52097208c8a43a5a24797af
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/106295
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/sal/CppunitTest_sal_rtl.mk b/sal/CppunitTest_sal_rtl.mk
index f559202c54d5..02b6c94e3d1b 100644
--- a/sal/CppunitTest_sal_rtl.mk
+++ b/sal/CppunitTest_sal_rtl.mk
@@ -31,6 +31,7 @@ $(eval $(call gb_CppunitTest_add_exception_objects,sal_rtl,\
 	sal/qa/rtl/ref/rtl_ref \
 	sal/qa/rtl/strings/nonconstarray \
 	sal/qa/rtl/strings/test_strings_replace \
+	sal/qa/rtl/strings/test_strings_defaultstringview \
 	sal/qa/rtl/strings/test_ostring \
 	sal/qa/rtl/strings/test_ostring_concat \
 	sal/qa/rtl/strings/test_ostring_stringliterals \