I checked with valgrind that on every run it reports
"==2247== Warning: unimplemented fcntl command: 1033
==2247== Thread 32:
==2247== Conditional jump or move depends on uninitialised value(s)
==2247== at 0x14B4107: SBAlgorithmCreateParagraph"
I tried to narrow down the part of memory which is uninitialized according to valgrind and it came out that if I will add in CreateParagraphContext function just after BidiChainInitialize additional code

for (int i = 0;i < length;++i) fixedTypes[i] = SBBidiTypeNil;

the valgrind is not reporting any problem.

I followed PopulateBidiChain code and it looks that in some cases it can omit initialization of some links in the chain. I do not understand sheenbidi well enough to say if this mean we have a data error in such case. Anyway application is not crashing because of it, the only visible problem so far is valgrind report.