| 1 | # serial 5 |
| 2 | # Check for flexible array member support. |
| 3 | |
| 4 | # Copyright (C) 2006, 2009-2019 Free Software Foundation, Inc. |
| 5 | # This file is free software; the Free Software Foundation |
| 6 | # gives unlimited permission to copy and/or distribute it, |
| 7 | # with or without modifications, as long as this notice is preserved. |
| 8 | |
| 9 | # Written by Paul Eggert. |
| 10 | |
| 11 | AC_DEFUN([AC_C_FLEXIBLE_ARRAY_MEMBER], |
| 12 | [ |
| 13 | AC_CACHE_CHECK([for flexible array member], |
| 14 | ac_cv_c_flexmember, |
| 15 | [AC_COMPILE_IFELSE( |
| 16 | [AC_LANG_PROGRAM( |
| 17 | [[#include <stdlib.h> |
| 18 | #include <stdio.h> |
| 19 | #include <stddef.h> |
| 20 | struct m { struct m *next, **list; char name[]; }; |
| 21 | struct s { struct s *p; struct m *m; int n; double d[]; };]], |
| 22 | [[int m = getchar (); |
| 23 | size_t nbytes = offsetof (struct s, d) + m * sizeof (double); |
| 24 | nbytes += sizeof (struct s) - 1; |
| 25 | nbytes -= nbytes % sizeof (struct s); |
| 26 | struct s *p = malloc (nbytes); |
| 27 | p->p = p; |
| 28 | p->m = NULL; |
| 29 | p->d[0] = 0.0; |
| 30 | return p->d != (double *) NULL;]])], |
| 31 | [ac_cv_c_flexmember=yes], |
| 32 | [ac_cv_c_flexmember=no])]) |
| 33 | if test $ac_cv_c_flexmember = yes; then |
| 34 | AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [], |
| 35 | [Define to nothing if C supports flexible array members, and to |
| 36 | 1 if it does not. That way, with a declaration like 'struct s |
| 37 | { int n; short d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack |
| 38 | can be used with pre-C99 compilers. |
| 39 | Use 'FLEXSIZEOF (struct s, d, N * sizeof (short))' to calculate |
| 40 | the size in bytes of such a struct containing an N-element array.]) |
| 41 | else |
| 42 | AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [1]) |
| 43 | fi |
| 44 | ]) |