Avoid UBSan invalid-null-argument

...as seen at least with --without-latest-c++ after
d0b2f5f65e80a4262425bb87d5716d7b4341dfea "pdfium: drop not needed annot.patch.1"
during CppunitTest_sw_core_text,

> workdir/UnpackedTarball/pdfium/core/fxcrt/string_data_template.cpp:76:20: runtime error: null pointer passed as argument 2, which is declared to never be null
> /usr/include/string.h:44:28: note: nonnull attribute specified here
>  #0 in fxcrt::StringDataTemplate<char>::CopyContents(char const*, unsigned long) at workdir/UnpackedTarball/pdfium/core/fxcrt/string_data_template.cpp:76:3
>  #1 in fxcrt::ByteString::ByteString(fxcrt::StringViewTemplate<char>, fxcrt::StringViewTemplate<char>) at workdir/UnpackedTarball/pdfium/core/fxcrt/bytestring.cpp:160:12
>  #2 in fxcrt::operator+(fxcrt::ByteString const&, fxcrt::ByteString const&) at workdir/UnpackedTarball/pdfium/core/fxcrt/bytestring.h:265:10
>  #3 in CPDFSDK_AppStream::SetAsTextField(absl::optional<fxcrt::WideString>) at workdir/UnpackedTarball/pdfium/fpdfsdk/cpdfsdk_appstream.cpp:1805:34
>  #4 in CPDFSDK_Widget::ResetAppearance(absl::optional<fxcrt::WideString>, CPDFSDK_Widget::ValueChanged) at workdir/UnpackedTarball/pdfium/fpdfsdk/cpdfsdk_widget.cpp:655:17
>  #5 in CPDFSDK_PageView::NewAnnot(CPDF_Annot*) at workdir/UnpackedTarball/pdfium/fpdfsdk/cpdfsdk_pageview.cpp:108:12
>  #6 in CPDFSDK_PageView::LoadFXAnnots() at workdir/UnpackedTarball/pdfium/fpdfsdk/cpdfsdk_pageview.cpp:566:45
>  #7 in CPDFSDK_FormFillEnvironment::GetOrCreatePageView(IPDF_Page*) at workdir/UnpackedTarball/pdfium/fpdfsdk/cpdfsdk_formfillenvironment.cpp:625:14
>  #8 in (anonymous namespace)::FormHandleToPageView(fpdf_form_handle_t__*, fpdf_page_t__*) at workdir/UnpackedTarball/pdfium/fpdfsdk/fpdf_formfill.cpp:169:39
>  #9 in FORM_OnAfterLoadPage at workdir/UnpackedTarball/pdfium/fpdfsdk/fpdf_formfill.cpp:730:37
>  #10 in vcl::pdf::(anonymous namespace)::PDFiumPageImpl::onAfterLoadPage(vcl::pdf::PDFiumDocument*) at vcl/source/pdf/PDFiumLibrary.cxx:764:5
>  #11 in testContentControlPDFFont::TestBody() at sw/qa/core/text/text.cxx:746:12

Change-Id: Iba73a9401eb10a8c03843dba038cd3a6eeeb0c4a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141210
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/external/pdfium/ubsan.patch b/external/pdfium/ubsan.patch
index bc9868244275..f1d3552b20d2 100644
--- a/external/pdfium/ubsan.patch
+++ b/external/pdfium/ubsan.patch
@@ -1,5 +1,14 @@
 --- core/fxcrt/string_data_template.cpp
 +++ core/fxcrt/string_data_template.cpp
+@@ -73,7 +73,7 @@
+                                                 size_t nLen) {
+   DCHECK_GE(nLen, 0);
+   DCHECK_LE(nLen, m_nAllocLength);
+-  memcpy(m_String, pStr, nLen * sizeof(CharType));
++  if (nLen != 0) memcpy(m_String, pStr, nLen * sizeof(CharType));
+   m_String[nLen] = 0;
+ }
+ 
 @@ -82,7 +82,8 @@ void StringDataTemplate<CharType>::CopyContentsAt(size_t offset,
    DCHECK_GE(offset, 0);
    DCHECK_GE(nLen, 0);