I took some time to narrow down the issue I mentioned and found: The c version detects and reports the incorrect use of: %define api.token.constructor The c++ version does not report this error. (it actually fails silently, leaving a couple of temp files around).
Source: %language "c++" // Try with and without this line %define api.token.constructor %start s %% s: 'x' | 'x'; %% Yes, the above is a silly example. My point is without that error message, there is no visual difference in the output between success or failure (for the c++ version). To borrow a phrase: "a bee expecting the window to magically vanish at some point" Well, that's what happened to me. Using Microsoft Visual Studio and a recommended plug-in, when I launch Bison, the build report shows 0 errors. There is an unexpected error return code of 1 and the build fails. So, armed with countless of previous cycles of "it always worked as expected", I began to chase the wind :) Thanks
