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dnl ## (Taken from pth-1.4.1)
dnl ##
dnl ## Check whether SVR4/SUSv2 makecontext(2), swapcontext(2) and
dnl ## friends can be used for user-space context switching
dnl ##
dnl ## configure.in:
dnl ## AC_CHECK_MCSC(<success-action>, <failure-action>)
dnl ##
AC_DEFUN(AC_CHECK_MCSC, [
AC_MSG_CHECKING(for usable SVR4/SUSv2 makecontext(2)/swapcontext(2))
AC_CACHE_VAL(ac_cv_check_mcsc, [
AC_TRY_RUN([
#include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
ucontext_t uc_child;
ucontext_t uc_main;
void child(void *arg)
{
if (arg != (void *)12345)
exit(1);
if (swapcontext(&uc_child, &uc_main) != 0)
exit(1);
}
int main(int argc, char *argv[])
{
FILE *fp;
void *stack;
/* the default is that it fails */
if ((fp = fopen("conftestval", "w")) == NULL)
exit(1);
fprintf(fp, "no\n");
fclose(fp);
/* configure a child user-space context */
if ((stack = malloc(64*1024)) == NULL)
exit(1);
if (getcontext(&uc_child) != 0)
exit(1);
uc_child.uc_link = NULL;
uc_child.uc_stack.ss_sp = (char *)stack+(32*1024);
uc_child.uc_stack.ss_size = 32*1024;
uc_child.uc_stack.ss_flags = 0;
makecontext(&uc_child, child, 2, (void *)12345);
/* switch into the user context */
if (swapcontext(&uc_main, &uc_child) != 0)
exit(1);
/* Fine, child came home */
if ((fp = fopen("conftestval", "w")) == NULL)
exit(1);
fprintf(fp, "yes\n");
fclose(fp);
/* die successfully */
exit(0);
}
],
ac_cv_check_mcsc=`cat conftestval`,
ac_cv_check_mcsc=no,
ac_cv_check_mcsc=no
)dnl
])dnl
AC_MSG_RESULT([$ac_cv_check_mcsc])
if test ".$ac_cv_check_mcsc" = .yes; then
ifelse([$1], , :, [$1])
else
ifelse([$2], , :, [$2])
fi
])dnl
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