alloca.h
/* Cfr https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Particular-Functions.html */
#if HAVE_ALLOCA_H
# include <alloca.h>
#elif defined __GNUC__
# define alloca __builtin_alloca
#elif defined _AIX
# define alloca __alloca
#elif defined _MSC_VER
# include <malloc.h>
# define alloca _alloca
#else
# include <stddef.h>
# ifdef __cplusplus
extern "C"
# endif
void *alloca (size_t);
#endif