alloca.h

/* Cfr https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.71/html_node/Particular-Functions.html */
#ifndef __VMS
#include <stdlib.h>
#include <stddef.h>
#ifdef HAVE_ALLOCA_H
# include <alloca.h>
#elif !defined alloca
# ifdef __GNUC__
#  define alloca __builtin_alloca
# elif defined _MSC_VER
#  include <malloc.h>
#  define alloca _alloca
# elif !defined HAVE_ALLOCA
#  ifdef  __cplusplus
extern "C"
#  endif
void *alloca (size_t);
# endif
#endif
#else /* __VMS */
#ifndef alloca
/* alloca is a built-in */
#include <builtins.h>
#define alloca(__x) __ALLOCA(__x)
#endif
#endif