Re: Why does sh in the build environment ignore SIGINT and SIGQUIT?

[Kaelyn <kaelyn.alexi@protonmail.com>]

Hi,

------- Original Message -------
On Monday, May 23rd, 2022 at 11:25 PM, Foo Chuan Wei <chuanwei.foo@hotmail.com> wrote:


> On 2022-05-23 03:14 +0000, Foo Chuan Wei wrote:
>
> > `(invoke "sh" "-c" "trap")` is merely a trivial example for
> > demonstrating that the shell ignores SIGINT and SIGQUIT. This might be
> > significant if the build step invokes the shell to do something more
> > significant (e.g. to build something).
> >
> > Anyway, I found that this behavior is possibly related to one specified
> > by POSIX [1]:
> >
> > > 2.11. Signals and Error Handling
> > >
> > > If job control is disabled (see the description of set -m) when the
> > > shell executes an asynchronous list, the commands in the list shall
> > > inherit from the shell a signal action of ignored (SIG_IGN) for the
> > > SIGINT and SIGQUIT signals.
>
>
> Maybe not. Guix's `invoke` procedure uses Guile's `system*` procedure,
> which ignores SIGINT and SIGQUIT as can be seen in Guile's source code:
> https://git.savannah.gnu.org/cgit/guile.git/tree/libguile/posix.c?h=v3.0.8#n1524
>
> > Do you have a solution to this problem?
>
>
> Guile's `system` procedure does not have this problem (compare
> `(system "bash -c trap")` with `(system* "bash" "-c" "trap")`).
> One possible solution is to replace `invoke` with `system`:

While `system` may not show the problem that `system*`, note that they aren't strictly interchangeable. To quote https://www.gnu.org/software/guile/manual/html_node/Processes.html#index-system_002a:

"system* is similar to system, but accepts only one string per-argument, and performs no shell interpretation. The command is executed using fork and execlp. Accordingly this function may be safer than system in situations where shell interpretation is not required."

Cheers,
Kaelyn

>
> diff --git a/gnu/packages/sml.scm b/gnu/packages/sml.scm
> index 04411c02c3..fafdba9a3f 100644
> --- a/gnu/packages/sml.scm
> +++ b/gnu/packages/sml.scm
> @@ -175,10 +175,14 @@ function interface, and a symbolic debugger.")
> "sml.boot.amd64-unix/SMLNJ-BASIS/.cm/amd64-unix/basis-common.cm"))
>
> ;; Build.
> - (invoke "./config/install.sh" "-default"
> - (if (string=? "i686-linux" ,(%current-system))
> - "32"
> - "64"))
> + (let ((exit-code
> + (system (string-append "./config/install.sh -default "
> + (if (string=? "i686-linux"
> + ,(%current-system))
> + "32"
> + "64")))))
> + (unless (zero? exit-code)
> + (error (format #f "Exit code: ~a" exit-code))))
>
> ;; Undo the binary patch.
> (for-each