From 8311c83f91a3127ccd2fe684e25bc60c5178d23b Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Thu, 7 Feb 2019 09:03:02 +0100 Subject: [PATCH] array_length: Make usable as a constant expression Do not use a statement expression in array_length, so that array_length can be used at file scope and as a constant expression. Instead, put the _Static_assert into a struct (as a declaration), and nest this in the expression using a sizeof expression. --- ChangeLog | 6 ++++++ include/array_length.h | 12 ++++++------ 2 files changed, 12 insertions(+), 6 deletions(-) diff --git a/ChangeLog b/ChangeLog index 1c477228f3..3270662983 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2019-02-07 Florian Weimer + + * include/array_length.h (array_length): Do not use a statement + expression and _Static_assert, so that array_length can be used at + file scope and as a constant expression. + 2019-02-07 Florian Weimer * support/xdlfcn.h (xdlmopen): Declare. diff --git a/include/array_length.h b/include/array_length.h index 65f583063d..db98a69899 100644 --- a/include/array_length.h +++ b/include/array_length.h @@ -22,12 +22,12 @@ /* array_length (VAR) is the number of elements in the array VAR. VAR must evaluate to an array, not a pointer. */ #define array_length(var) \ - __extension__ ({ \ - _Static_assert (!__builtin_types_compatible_p \ - (__typeof (var), __typeof (&(var)[0])), \ - "argument must be an array"); \ - sizeof (var) / sizeof ((var)[0]); \ - }) + (sizeof (var) / sizeof ((var)[0]) \ + + 0 * sizeof (struct { \ + _Static_assert (!__builtin_types_compatible_p \ + (__typeof (var), __typeof (&(var)[0])), \ + "argument must be an array"); \ + })) /* array_end (VAR) is a pointer one past the end of the array VAR. VAR must evaluate to an array, not a pointer. */