How does it work when I run two ninja commands (the 2nd begins before the 1st completes) in the same directory. Will it cause undefined behaviors?

[刘铭名]

Hi,

    I'm wondering how it works when I run two ninja commands (the 2nd begins before the 1st completes) in the same directory.

     The 1st one is still linking, but the 2nd one is re-building a target (that's possibly being used) in the 1st command anytime.

      I didn't see a violent warning message or error, so wondering if it would cause undefined behavior, or introduces bugs silently.

[Mingming Liu]

frt, https://stackoverflow.com/questions/70173482/how-does-it-work-when-i-run-two-ninja-commands-the-2nd-begins-before-the-1st-co/70173754#70173754 discussed the same question.

And to quote from the response, the short answer is

1) There is no blocking mechanism implemented in ninja to protect against concurrent execution

2) The behavior here will be a result of a race condition - two processes access, write and read, to the same set of files concurrently. That's nothing out of the ordinary