enable ax_restrict

re-format docs: autoconf-archive is pretty strict
gcc-9.2 on fedora has it fixed.

enable it.  we do have several small inlined functions with loops on arrays,
so it might affects us. See GH #141

configure.ac

@@ -103,7 +103,6 @@ ac_cv_func_realloc_0_nonnull=yes
 AC_CHECK_HEADERS([stdlib.h string.h stddef.h unistd.h malloc.h wchar.h ctype.h \
                   libgen.h getopt.h alloca.h valgrind/valgrind.h])
 AX_INCLUDE_STRCASECMP
-# AX_RESTRICT
 
 # Don't bother testing for libps headers if libps is not available.
 if test yes = "$libredwg_have_libps" ; then
@@ -223,6 +222,21 @@ case $host in
 esac
 dnl x86_64-mingw-w64-gcc-9.2 is seriously broken, and not just mingw-w64
 
+dnl --enable-debug sets DEBUG_CLASSES, will crash acad import
+AC_MSG_CHECKING([--enable-debug])
+AC_ARG_ENABLE([debug],AS_HELP_STRING([--enable-debug],[
+    Enable unstable DEBUG_CLASSES (default: no).]),
+  [if test x$ac_compiler_gnu = xyes; then
+    CFLAGS="`echo $CFLAGS|sed 's,-O2,,'` -fno-omit-frame-pointer"
+  fi
+  CFLAGS="$CFLAGS -DDEBUG_CLASSES"]
+  AC_MSG_RESULT([yes]),
+  AC_MSG_RESULT([no (default)]))
+AM_CONDITIONAL([ENABLE_DEBUG], [test x$enable_debug = xyes])
+
+AX_ADD_FORTIFY_SOURCE
+AX_RESTRICT
+
 dnl Feature: --disable-write
 AC_MSG_CHECKING([--disable-write])
 AC_ARG_ENABLE([write],AS_HELP_STRING([--disable-write],[
@@ -250,20 +264,6 @@ AC_CHECK_FUNCS([setenv],[],
     [AC_MSG_RESULT([setenv not needed. no --enable-trace.])]
     ))
 
-dnl --enable-debug sets DEBUG_CLASSES, will crash acad import
-AC_MSG_CHECKING([--enable-debug])
-AC_ARG_ENABLE([debug],AS_HELP_STRING([--enable-debug],[
-    Enable unstable DEBUG_CLASSES (default: no).]),
-  [if test x$ac_compiler_gnu = xyes; then
-    CFLAGS="`echo $CFLAGS|sed 's,-O2,,'` -fno-omit-frame-pointer"
-  fi
-  CFLAGS="$CFLAGS -DDEBUG_CLASSES"]
-  AC_MSG_RESULT([yes]),
-  AC_MSG_RESULT([no (default)]))
-AM_CONDITIONAL([ENABLE_DEBUG], [test x$enable_debug = xyes])
-
-AX_ADD_FORTIFY_SOURCE
-
 dnl --disable-dxf only useful for faster debug/test cycles
 AC_MSG_CHECKING([--disable-dxf])
 AC_ARG_ENABLE([dxf],AS_HELP_STRING([--disable-dxf],[

m4/ax_restrict.m4

@@ -1,5 +1,5 @@
 # ===========================================================================
-#  https://www.gnu.org/software/autoconf-archive/ax_restrict.html
+#       https://www.gnu.org/software/autoconf-archive/ax_restrict.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -9,10 +9,11 @@
 # DESCRIPTION
 #
 #   This macro checks if the C99 restrict keyword is broken with the current
-#   compiler and optimizations settings. If broken, it undefines restrict to do
-#   no harm. As of 2019 gcc since 5.0 and clang since 6.0 (June 2017) are known to be
-#   broken and not yet fixed. See https://github.com/rust-lang/rust/issues/54878
-#   with the links to the gcc and clang tickets.
+#   compiler and optimizations settings. If broken, it undefines restrict to
+#   do no harm. As of 2019 gcc since 5.0 and clang since 6.0 (June 2017) are
+#   known to be broken and not yet fixed. See
+#   https://github.com/rust-lang/rust/issues/54878 with the links to the gcc
+#   and clang tickets.
 #
 # LICENSE
 #

src/config.h.in

@@ -217,6 +217,9 @@
 /* Define to rpl_realloc if the replacement function should be used. */
 #undef realloc
 
+/* If restrict is broken with this compiler */
+#undef restrict
+
 /* Define to `unsigned int' if <sys/types.h> does not define. */
 #undef size_t