Reading from io.popen handle crashes in release build Lua

[Shane Liesegang <shane@...>]

I have this bit of (what I think is) innocuous Lua code: 

  local f = assert(io.popen(path .. " -version", 'r'))
  local s = assert(f:read('*a'))
  f:close()

Where
 "path" is a string pointing to a configuration program, and I do some 
processing on "s" afterwards to make sure it's at the correct version 
before proceeding. 

This worked fine in Lua 5.1.5, and it works fine when I build Lua 
5.2.1 in debug mode, but when I have a release version of the lua 
executable, it crashes on the second line with "Interrupted system 
call." 

I'm not sure which optimization in my particular Release 
configuration is  causing the issue, but I figured it worth asking 
if anyone had an idea of what might cause a problem like this, what 
might have changed in io between 5.1 and 5.2, etc. 

Is there a new, better way to get the output from an external program?