It looks as if there's an access violation in Hyperscan. Can you help find & fix it? I made simple updates to the Hyperscan library to build a DLL for Windows. When I compile the DLL using Release mode, it shows access violations in FDR_EXEC_TEDDY when attempting a simple match. To reproduce (replace BOOST_ROOT with your BOOST_ROOT): git clone git@github.com:wurp/hyperscan.git mkdir access-violation cd access-violation cmake -G "Visual Studio 15 2017 Win64" -DBUILD_SHARED_LIBS=ON -DBOOST_ROOT:PATH=c:\CxCache\boost.1.67.0.0\lib\native\include .. cmake --build . --config Release bin\hscheck.exe I put the code that evokes the AV in tools/hscheck/main.cpp. The crux of it is this: hs_database_t* pRegexDatabase = nullptr; hs_compile_error_t *compile_err = nullptr; hs_error_t hsError = hs_compile( "Sample?Value", 0, HS_MODE_BLOCK, nullptr, &pRegexDatabase, &compile_err); if (hsError != HS_SUCCESS) { printf("Dead 1\n"); exit(-2); } hs_scratch_t* pScratch = nullptr; hsError = hs_alloc_scratch(pRegexDatabase, &pScratch); if (hsError != HS_SUCCESS) { printf("Dead 2\n"); exit(-2); } bool matched = false; printf("Scan 1\n"); hsError = hs_scan( pRegexDatabase, "Sample\?Value", 12, 0, pScratch, blowupEventHandler, &matched); if (hsError != HS_SUCCESS) { printf("Dead 3\n"); exit(-2); } printf("Scan 2\n"); hsError = hs_scan( pRegexDatabase, "SampleeValue", 12, 0, pScratch, blowupEventHandler, &matched); if (hsError != HS_SUCCESS) { printf("Dead 4\n"); exit(-2); } printf("good exit"); The output shows "Scan 1", but never shows "Scan 2" or any "Dead"/"good" message. Note that I see no AV when building with /MT (non-DLL runtime) nor when compiling with /MDd (DLL runtime with debug info). Thanks! Bobby