Initial report buried here. Salient details are: when previewing results of modifying a <math> expression on English WikiSource with HHVM enabled, this error is presented:
Failed to parse (Missing <code>texvc</code> executable. Please see math/README to configure.):
\scriptstyle{i=\frac{702\cdot25}{2\times10}=35\cdot11,\quad\mu=1\cdot738} .
\scriptstyle{i=\frac{702\cdot25}{2\times10}=35\cdot11,\quad\mu=1\cdot738} .
Notes:
- The second line of the error message is simply informational regarding the input LaTeX string and is not likely pertinent to this report.
- The error reliably goes away when HHVM is deselected from Beta choices.
- Reliably returns when both HHVM reenabled and the previewed formula is tweaked to force re-evaluation.
- There is no problem displaying cached results irrespective of HHVM state.
- There may be further significance in the fact that <code> does not appear to have been parsed by the error processor.
- Verified similar results on English WikiPedia.