lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

On 30 Jan 2019, at 16:11, Roberto Ierusalimschy <> wrote:

This exists since Lua 5.2. The culprit is the exit code on Windows having a different format than on unix/posix. The latter has 0-255 as common ground and mostly anything else is undefined. But on Windows the exit code is a 32bit signed integer.

Now this code:
Treats -1 as a special case, and goes looking for an error message here:

This results in “No error” in the windows case of -1, since it is a valid exit code.

(Sorry for such a late reply...)

I don't understand the problem here. The documentation for 'system' in
Windows says this:

 A return value of -1 indicates an error, and errno is set to one of the
 following values: […]

It’s in the preceding line: 
> It returns the value 0 only if the command interpreter returns the value 0. A return
> value of - 1 indicates an error, and errno is set to one of the following values:

And this makes the result of -1 ambiguous, because both an error and a -1 return value from the command result in a -1 result.

I think the proper approach would be to reset `errno` before the `system` call and then check for: `stat` being -1, AND `errno` being non-0.


-- Roberto