Copy makecontext macro from pthRELEASE-0_5_0-LIVINGABROADBRANCH-RELEASE-0_5_0-ROOT

Original commit message from CVS:
Copy makecontext macro from pth

1 files changed, 79 insertions, 0 deletions

diff --git a/m4/gst-mcsc.m4 b/m4/gst-mcsc.m4
new file mode 100644
index 0000000..ffcbe76
--- /dev/null
+++ b/m4/gst-mcsc.m4
@@ -0,0 +1,79 @@
+
+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
+