dnl configure.ac — nulsl-libc, a very lightweight C17 libc for Linux.
dnl
dnl Static-only on purpose: the dynamic linker is a memory tax we refuse to
dnl pay (see docs/architecture.md). libc.a is a plain archive, so no libtool.
dnl
dnl IMPORTANT: never run ./configure at the repository root. The root holds a
dnl hand-written driver Makefile that builds into bin/{release,debug}; the
dnl guard below refuses to overwrite it.

AC_PREREQ([2.71])
AC_INIT([nulsl-libc], [0.1.0], [], [nulsl-libc],
        [https://git.spectoria.dev/The-Null-Linux-Project/nulsl-libc])
AC_CONFIG_SRCDIR([include/stdio.h])
AC_CONFIG_AUX_DIR([build-aux])
AC_CANONICAL_HOST

AM_INIT_AUTOMAKE([foreign subdir-objects])

dnl C17, and only C17 (project guideline #1). Modern autoconf ships no
dnl AC_PROG_CC_C17 macro, so prove it with a compile test instead.
AC_PROG_CC
saved_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -std=c17"
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#if __STDC_VERSION__ < 201710L
#error "not C17"
#endif
], [])],
    [],
    [AC_MSG_ERROR([nulsl-libc requires a C17 compiler (GCC >= 8 or Clang >= 6); -std=c17 was rejected])])
CFLAGS="$saved_CFLAGS"

dnl Target validation: Linux on x86_64, for now.
AS_CASE([$host_os],
        [linux*], [],
        [AC_MSG_ERROR([nulsl-libc currently targets Linux only (configured for $host_os)])])
AS_CASE([$host_cpu],
        [x86_64], [],
        [AC_MSG_ERROR([nulsl-libc currently targets x86_64 only (configured for $host_cpu); src/arch/ is where new ports go])])

dnl Plain archives need ar/ranlib; no libtool, no shared objects.
AC_CHECK_TOOL([AR], [ar])
AC_PROG_RANLIB

dnl Refuse in-tree configuration: it would clobber the committed driver
dnl Makefile that dispatches into bin/{release,debug}.
AS_IF([test "x$srcdir" = "x." && test -f Makefile],
      [AC_MSG_ERROR([in-tree builds are disabled — run 'make release' or 'make debug' from the repository root instead])])

AC_CONFIG_FILES([Makefile])
AC_OUTPUT