On 11/26/20 10:31 AM, Michael Kerrisk (man-pages) wrote: > Hello Davide, > > On Thu, 26 Nov 2020 at 01:01, Davide Giorgio <davide@xxxxxxxxxxxxxxxx> wrote: >> >> Good morning, >> >> reading the pivot_root man page >> (https://man7.org/linux/man-pages/man2/pivot_root.2.html) >> there seems to be an error in the example source program >> "pivot_root_demo.c". >> In particular, there is a wrong check on the return value of mount(2). >> https://man7.org/linux/man-pages/man2/mount.2.html#RETURN_VALUE >> >> The error is in this line >> if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL) == 1) >> >> that should be >> if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL) == -1) >> >> >> Thank you for your work, kind regards > > Thanks! Fixed! Hi Michael, What about fixing this from a different approach: instead of comparing against -1 for functions that either return either 0 or -1, we can include those functions in the greater family of functions that return either 0 or non-zero (error code). I propose comparing against 0: - if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL) == 1) + if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL) != 0) I consider this to be safer, simpler, and although negligible, also faster. What are your thoughts? Thanks, Alex > > Cheers, > > Michael >
