Hello,
I manage to find a solution: define a new procedure 'system**' which is
implemented in C using fork-exec-waitpid. The code is in the attchment.
To compile the C extension, run:
$ gcc -o libguile-system_star_star.so -shared -fPIC \
`pkg-config --cflags guile-2.2` -O2 -Wall -Wextra system_star_star.c
To test the C extension, try running something like:
(use-modules (ice-9 threads))
(load-extension "./libguile-system_star_star" "init_system_star_star")
(define n 10000)
(define s (make-string n #\s))
(define l (make-list n s))
(define main
(lambda _
(parallel (system** "echo" "foo" "bar")
(apply system** l)
(system** "echo" "foo" "bar")
(apply system** l))))
C-c should terminate the program.
My first solution was to use 'primitive-fork'. But it didn't work,
because guile warned me that 'primitive-fork' shouldn't be called in a
multithreaded program. I want to find out why. So I read the man-page
and it says after forking in a multithread program, it is only safe to
call async-safe functions. So I re-implement the whole thing in C and
exec right after forking. This is how I come up with the current
solution.
/* Copyright (C) 2017 Alex Vong <alexvong1...@gmail.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 3 of
* the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA
*/
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <libguile.h>
static SCM
system_star_star(SCM prog, SCM args)
{
SCM prog_args = scm_cons(prog, args);
size_t len = scm_to_size_t(scm_length(prog_args));
char **argv = scm_gc_malloc((len + 1) * sizeof(char *), "argv");
for (size_t k = 0; k < len; ++k)
{
SCM arg = SCM_CAR(prog_args);
size_t len = scm_c_string_length(arg);
argv[k] = scm_gc_malloc_pointerless(len + 1, "argv[k]");
scm_to_locale_stringbuf(arg, argv[k], len);
argv[k][len] = '\0';
prog_args = SCM_CDR(prog_args);
}
argv[len] = NULL;
int status = 0;
pid_t pid = fork();
if (pid == -1)
scm_syserror("system**");
if (pid == 0) /* child */
{
execvp(argv[0], argv);
_exit(127);
}
else /* parent */
{
if (waitpid(pid, &status, 0) == -1)
scm_syserror("system**");
}
return scm_from_int(status);
}
void
init_system_star_star(void)
{
scm_c_define_gsubr("system**", 1, 0, 1, system_star_star);
}
Cheers, Alex Alex Vong <alexvong1...@gmail.com> writes: > Hello, > > When running the external program "yes" in shell, > > $ yes > > We can terminate the process by pressing C-c. > > However, when running the external program "yes" in guile, > > $ guile -c '(system* "yes")' > > We cannot terminate the process by pressing C-c, > but we can suspend it by pressing C-z. > > Why is that? Is there any way I can terminate the process by pressing > C-c? > > Thanks, > Alex
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