Yeah, exactly. Thanks for this very interesting discussion. Bye On Thursday, October 26, 2023, Gabriel Ravier <gabrav...@gmail.com> wrote:
> On 10/26/23 11:55, Oğuz wrote: > >> On Wed, Oct 25, 2023 at 9:47 PM Gabriel Ravier <gabrav...@gmail.com> >> wrote: >> > Isn't this a similar situation to e.g. `getuid`/`geteuid`/etc. failures >> >> Not similar enough to draw a conclusion. Unlike system(), those functions >> are not part of the language defined by ISO C, but the operating system >> interface defined by POSIX. How operating systems are designed is outside >> the scope of ISO C; it can not require that system(NULL) perform additional >> checks to determine if the command processor is currently available, as it >> might require the user to enter his credentials, have a working internet >> connection, etc. And an environment where the command shell is unavailable >> is not supported by POSIX, so system(NULL) always returns non-zero. >> >> I don't think POSIX allows (or should allow) system(NULL) to return 0, >> but feel free to request clarification. >> > > > POSIX does not allow `system(NULL)` to return 0, yes. That's very clear in > the standard - it says as much directly. I do not see how that impacts > behavior in a non-conforming environment - POSIX does not define the > behavior of a non-conforming environment, does it ? (the very idea seems > tautologically false...) > > I also do not see how POSIX can forbid tests that could only fail in an > environment which does not conform to POSIX - by the very definition of > that statement, this means `system(NULL)` will still always return non-0 in > a POSIX-confirming environment. Those tests are not observable to any > program executing in a POSIX-conforming environment - from the point of > view of the standard they may as well not occur, so POSIX cannot impose > anything upon them. > > (I suppose you could say that makes things needlessly slower when > executing in a POSIX-conforming environment, but I see no requirement in > the standard that implementations be fast) > > >> >> -- >> Oğuz >> >> > -- Oğuz
