Perhaps I can save Paul an explanation: running the shell has some time cost so if the command looks simple enough then make executes it without passing to any shell.
On 13 October 2015 at 15:11, Mark Galeck <mark_gal...@pacbell.net> wrote: > Thank you Paul! > > Well, the recipe I am using is the simplest possible recipe: > all: echo $(SHELL) > > OK, what do you mean by "runs the command directly rather than invoking a > shell" > > I tested that possibility (even though the manual clearly says that is not > the case). I custom modified /bin/sh, then ran that, so that my > _current_shell_ was the modified one. Then _in_that_context_ ran GNU Make > with the simple recipe. > I had shell modified so that each time it interpreted a command, it would > print something to a log file. > Nope. When I ran GNU Make , the log file was not updated, so that meant, the > current modified shell, was not interpreting any command. > > From: Paul Smith <psm...@gnu.org> > To: Mark Galeck <mark_gal...@pacbell.net> > Cc: "help-make@gnu.org" <help-make@gnu.org> > Sent: Tuesday, October 13, 2015 5:02 AM > Subject: Re: how to use a different /bin/sh with GNU Make? > > On Tue, 2015-10-13 at 04:35 +0000, Mark Galeck wrote: >> as root, I replaced the default /bin/sh with a shell compiled by me >> with custom changes. I expected GNU Make will use that shell by >> default , but it does not - it still uses the original /bin/sh (which >> was really bash) even though it is not there anymore. > > It would be very helpful if you provided an example of the recipe you're > using. Without that we can only speculate. > > GNU make contains a special "fast path" capability. If it knows that > the shell is a POSIX-compliant shell (because the shell is one of a set > of known POSIX-compliant shells such as /bin/sh, /bin/bash, or others... > for the complete list see the unix_shells[] array in the jobs.c file in > the GNU make source code), and it determines that the recipe is "simple > enough": it's a single command, has no IO redirection or pipes, the > quoting is straightforward, and there are no shell variables in it, then > make runs the command directly rather than invoking a shell. > > So for example, this recipe is run directly by make rather than starting > > > a shell: > > cc -Wall -o foo.o -c foo.c > > but this recipe would always start a shell: > > cc -Wall -o foo.o -c foo.c; echo "Compilation complete" > > If you want to force make to always start a shell and never use the fast > path the best way is to name your shell something else, like /bin/mgsh > or something, then set make's SHELL variable to that path. Since make > is no longer sure if your shell is a POSIX shell, it will never use the > fast path. > > > > > _______________________________________________ > Help-make mailing list > Help-make@gnu.org > https://lists.gnu.org/mailman/listinfo/help-make -- You could help some brave and decent people to have access to uncensored news by making a donation at: http://www.thezimbabwean.co.uk/friends/ _______________________________________________ Help-make mailing list Help-make@gnu.org https://lists.gnu.org/mailman/listinfo/help-make
