fix a bug loading functions with 8 or more arguments

* libguile/vm-i-loader.c: A combination of superstition and a bugfix:
  make sure that we treat bits as being of a type as wide as we think it
  is, and, more importantly, allow for programs with 8 <= nargs < 16.

diff --git a/libguile/vm-i-loader.c b/libguile/vm-i-loader.c
index db0ee9b..3b232cb 100644 (file)
--- a/libguile/vm-i-loader.c
+++ b/libguile/vm-i-loader.c
@@ -144,19 +144,21 @@ VM_DEFINE_LOADER (load_program, "load-program")
       int i = SCM_I_INUM (x);
       if (-128 <= i && i <= 127)
        {
+          scm_t_uint8 c = (scm_t_uint8)i;
          /* 8-bit representation */
-         p->nargs = (i >> 6) & 0x03;   /* 7-6 bits */
-         p->nrest = (i >> 5) & 0x01;   /*   5 bit  */
-         p->nlocs = (i >> 2) & 0x07;   /* 4-2 bits */
-         p->nexts = i & 0x03;          /* 1-0 bits */
+         p->nargs = (c >> 6) & 0x03;   /* 7-6 bits */
+         p->nrest = (c >> 5) & 0x01;   /*   5 bit  */
+         p->nlocs = (c >> 2) & 0x07;   /* 4-2 bits */
+         p->nexts = c & 0x03;          /* 1-0 bits */
        }
       else
        {
+          scm_t_uint16 s = (scm_t_uint16)i;
          /* 16-bit representation */
-         p->nargs = (i >> 12) & 0x07;  /* 15-12 bits */
-         p->nrest = (i >> 11) & 0x01;  /*    11 bit  */
-         p->nlocs = (i >> 4)  & 0x7f;  /* 10-04 bits */
-         p->nexts = i & 0x0f;          /* 03-00 bits */
+         p->nargs = (s >> 12) & 0x0f;  /* 15-12 bits */
+         p->nrest = (s >> 11) & 0x01;  /*    11 bit  */
+         p->nlocs = (s >> 4)  & 0x7f;  /* 10-04 bits */
+         p->nexts = s & 0x0f;          /* 03-00 bits */
        }
     }
   else