Debugging the failed LibreOffice rawhide i686 build <https://koji.fedoraproject.org/koji/taskinfo?taskID=27975925>, it looks like the CLucene that LibreOffice builds against has been built with float_t (from math.h) being a typedef for (80 bit) long double instead of the usual (32 bit) float:

/usr/include/CLucene/document/Field.h defines a class Field with last data member

> 	float_t boost;

and LibreOffice creates a Field instance on the heap with

>     doc->add(*_CLNEW Field(_T("path"), &aPath[0], Field::STORE_YES | Field::INDEX_UNTOKENIZED));

(HelpIndexer::helpDocument in helpcompiler/source/HelpIndexer.cxx).  LibreOffice calls ::operator new with its idea of sizeof(Field) based on float_t being a typedef for float, but CLucene's Field ctor writes a long double into the boost member, witness the "fstpt 0x18(%esi)" instruction in _ZN6lucene8document5FieldC2EPKwPNS_4util6ReaderEi (/lib/libclucene-core.so.1), which causes a write of 10 - 4 = 6 bytes past the end of the allocated memory.

And running the code under valgrind (`LD_LIBRARY_PATH=/builddir/build/BUILD/libreoffice-6.0.5.2/instdir/program valgrind workdir/LinkTarget/Executable/HelpIndexer -lang en-US -mod help -dir /builddir/build/BUILD/libreoffice-6.0.5.2/workdir/Extension/nlpsolver/root/help/en-US`) shows

> ==88== Invalid write of size 4
> ==88==    at 0x4AFADEA: lucene::document::Field::Field(wchar_t const*, wchar_t const*, int, bool) (in /usr/lib/libclucene-core.so.2.3.3.4)
> ==88==    by 0x4CE5DC3: HelpIndexer::helpDocument(rtl::OUString const&, lucene::document::Document*) const (HelpIndexer.cxx:118)
> ==88==    by 0x4CE6649: HelpIndexer::indexDocuments() (HelpIndexer.cxx:64)
> ==88==    by 0x10985F: main (HelpIndexer_main.cxx:81)
> ==88==  Address 0x7541404 is 0 bytes after a block of size 28 alloc'd
> ==88==    at 0x4831829: operator new(unsigned int) (vg_replace_malloc.c:328)
> ==88==    by 0x4CE5DA5: HelpIndexer::helpDocument(rtl::OUString const&, lucene::document::Document*) const (HelpIndexer.cxx:118)
> ==88==    by 0x4CE6649: HelpIndexer::indexDocuments() (HelpIndexer.cxx:64)
> ==88==    by 0x10985F: main (HelpIndexer_main.cxx:81)
> ==88== 
> ==88== Invalid write of size 2
> ==88==    at 0x4AFADEA: lucene::document::Field::Field(wchar_t const*, wchar_t const*, int, bool) (in /usr/lib/libclucene-core.so.2.3.3.4)
> ==88==    by 0x4CE5DC3: HelpIndexer::helpDocument(rtl::OUString const&, lucene::document::Document*) const (HelpIndexer.cxx:118)
> ==88==    by 0x4CE6649: HelpIndexer::indexDocuments() (HelpIndexer.cxx:64)
> ==88==    by 0x10985F: main (HelpIndexer_main.cxx:81)
> ==88==  Address 0x7541408 is 4 bytes after a block of size 28 alloc'd
> ==88==    at 0x4831829: operator new(unsigned int) (vg_replace_malloc.c:328)
> ==88==    by 0x4CE5DA5: HelpIndexer::helpDocument(rtl::OUString const&, lucene::document::Document*) const (HelpIndexer.cxx:118)
> ==88==    by 0x4CE6649: HelpIndexer::indexDocuments() (HelpIndexer.cxx:64)
> ==88==    by 0x10985F: main (HelpIndexer_main.cxx:81)
[...]

(CLucene's cmake machinery has a src/shared/cmake/DefineFloat.cmake that would "SET ( _FLT_EVAL_METHOD 2 )" if "NOT HAVE_SYMBOL_FLOAT_T".  In the C standard, if the value of FLT_EVAL_METHOD (float.h) is 2, float_t (math.h) will be a typedef for long double.)