This patch fixes a memory leak when capturing and resuming delimited
continuations intensively, as is the case with the Shepherd 0.9+:

  https://issues.guix.gnu.org/59021

diff --git a/libguile/vm.c b/libguile/vm.c
index 6fd5c554f..516bae773 100644
--- a/libguile/vm.c
+++ b/libguile/vm.c
@@ -165,11 +165,13 @@ capture_stack (union scm_vm_stack_element *stack_top,
                scm_t_dynstack *dynstack, uint32_t flags)
 {
   struct scm_vm_cont *p;
+  size_t stack_size;
 
-  p = scm_gc_malloc (sizeof (*p), "capture_vm_cont");
-  p->stack_size = stack_top - sp;
-  p->stack_bottom = scm_gc_malloc (p->stack_size * sizeof (*p->stack_bottom),
-                                   "capture_vm_cont");
+  stack_size = stack_top - sp;
+  p = scm_gc_malloc (sizeof (*p) + stack_size * sizeof (*p->stack_bottom),
+                     "capture_vm_cont");
+  p->stack_size = stack_size;
+  p->stack_bottom = (void *) ((char *) p + sizeof (*p));
   p->vra = vra;
   p->mra = mra;
   p->fp_offset = stack_top - fp;