ffi: use expressions for bit field width also.

* ffi.c (ffi_type_compile): Evaluate width argument
of sbit and ubit type as as expression.

* txr.1: Documented.

2 files changed, 6 insertions, 5 deletions

diff --git a/ffi.c b/ffi.c
index db7ae8cd..84ec6b9f 100644
--- a/ffi.c
+++ b/ffi.c
@@ -2341,7 +2341,7 @@ val ffi_type_compile(val syntax)
                                    ffi_carray_put, ffi_carray_get,
                                    0, 0, 0, eltype);
     } else if (sym == sbit_s || sym == ubit_s) {
-      val nbits = cadr(syntax);
+      val nbits = ffi_eval_expr(cadr(syntax), nil, nil);
       cnum nb = c_num(nbits);
       val type = make_ffi_type_builtin(syntax, integer_s, 0, 0,
                                        &ffi_type_void,
diff --git a/txr.1 b/txr.1
index a9ba02de..c0f40cc3 100644
--- a/txr.1
+++ b/txr.1
@@ -53541,9 +53541,9 @@ be extended.
 
 Some constituents of compound type syntax are expressions which evaluate to
 integer values: the dimension value for array types, the size for buffers,
-and the value expressions for enumeration constants are such expressions.
-These expressions allow full use of \*(TL. They are evaluated without
-visibility into any apparent surrounding lexical scope.
+the width for bitfields and the value expressions for enumeration constants are
+such expressions. These expressions allow full use of \*(TL. They are
+evaluated without visibility into any apparent surrounding lexical scope.
 
 Some predefined types which are provided are in fact typedef names.
 For instance, the
@@ -54453,7 +54453,8 @@ Bitfields of any other type are not supported.
 
 The
 .meta width
-parameter of the type indicates the number of bits. It may range from
+parameter of is an expression evaluated in the top-level environment,
+indicates the number of bits. It may range from
 zero to the number of bits in the
 .code uint
 type.