tests: fix placement of test coroutine stacks

placing the coroutine stacks on the main coroutine stack is undefined behavior.
found with clang -fstack-protector-strong.

fixes #75

Signed-off-by: Ariadne Conill <ariadne@ariadne.space>

Author: kaniini

test_libucontext.c

@@ -54,12 +54,12 @@ static void f2 (void) {
 }
 
 
-int main (int argc, const char *argv[]) {
-	char st1[8192];
-	char st2[8192];
-	volatile int done = 0;
+char st1[8192];
+char st2[8192];
+volatile int done = 0;
 
 
+int main (int argc, const char *argv[]) {
 	/* poison each coroutine's stack memory for debugging purposes */
 	memset(st1, 'A', sizeof st1);
 	memset(st2, 'B', sizeof st2);

test_libucontext_posix.c

@@ -54,10 +54,12 @@ static void f2 (void) {
 }
 
 
+char st1[8192];
+char st2[8192];
+volatile int done = 0;
+
+
 int main (int argc, const char *argv[]) {
-	char st1[8192];
-	char st2[8192];
-	volatile int done = 0;
 
 
 	/* poison each coroutine's stack memory for debugging purposes */