diff --git a/.gitignore b/.gitignore
index cb8812c6..f1f12990 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,6 +22,9 @@ reconfigure.sh
 */Depend*.tmp
 .deps/
 database/database.h
+# autoconf config header, generated by ./configure (in-tree location; out-of-tree
+# it lives under the build dir's include/ and is covered by the build-dir rules).
+magic/autoconf/config.h
 
 # Editor / OS cruft
 .*.swp
diff --git a/scripts/configure b/scripts/configure
index 7dfa7d2a..5f93d65c 100755
--- a/scripts/configure
+++ b/scripts/configure
@@ -9398,6 +9398,24 @@ ac_config_files="$ac_config_files scripts/makedbh:scripts/makedbh.in"
 
 ac_config_files="$ac_config_files rules.mak:rules.mak"
 
+
+if test "`cd $srcdir && pwd`" = "`pwd`" ; then
+  magic_config_header=magic/autoconf/config.h
+else
+  magic_config_header=include/magic/autoconf/config.h
+fi
+mkdir -p "`dirname $magic_config_header`"
+{
+  echo "/* $magic_config_header -- generated by configure; DO NOT EDIT. */"
+  echo "/* Every autoconf define (>= all -D options on the compiler lines). */"
+  echo "#ifndef _MAGIC_AUTOCONF_CONFIG_H"
+  echo "#define _MAGIC_AUTOCONF_CONFIG_H 1"
+  grep '^#define ' confdefs.h | sort -u
+  echo "#endif /* _MAGIC_AUTOCONF_CONFIG_H */"
+} > "$magic_config_header"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: created config header $magic_config_header" >&5
+$as_echo "$as_me: created config header $magic_config_header" >&6;}
+
 cat >confcache <<\_ACEOF
 # This file is a shell script that caches the results of configure
 # tests run on this system so they can be shared between configure
diff --git a/scripts/configure.in b/scripts/configure.in
index a703cdc1..c928c238 100644
--- a/scripts/configure.in
+++ b/scripts/configure.in
@@ -2002,6 +2002,38 @@ dnl Copy rules.mak into the build top (it has no @...@ substitutions; this just
 dnl places it next to the generated defs.mak so a single ${MAGICDIR} resolves
 dnl both `include`s in every subdir Makefile out-of-tree).
 AC_CONFIG_FILES([rules.mak:rules.mak])
+
+dnl Emit an autoconf config header, available to the tree as
+dnl   #include <magic/autoconf/config.h>
+dnl It carries every autoconf define (i.e. at least all the -D options that
+dnl appear on the compiler command lines, plus anything else configure knows).
+dnl We build it here, from confdefs.h, rather than via AC_CONFIG_HEADERS on
+dnl purpose: that keeps @DEFS@ (hence the command lines and the whole build)
+dnl exactly as-is, so the header is a pure additional artifact with no consumers
+dnl yet.  confdefs.h holds every AC_DEFINE and is still present at this point
+dnl (AC_OUTPUT removes it), so it must run before AC_OUTPUT.
+dnl
+dnl Location mirrors the generated database.h (see defs.mak GENINC): at the
+dnl build top when in-tree (build dir == source dir), else under a clean
+dnl include/ subdir so the -I include/ rule finds <magic/autoconf/config.h> and
+dnl the raw build dir is never on the search path.  Regenerated on every
+dnl ./configure; the directory is created on demand.
+if test "`cd $srcdir && pwd`" = "`pwd`" ; then
+  magic_config_header=magic/autoconf/config.h
+else
+  magic_config_header=include/magic/autoconf/config.h
+fi
+mkdir -p "`dirname $magic_config_header`"
+{
+  echo "/* $magic_config_header -- generated by configure; DO NOT EDIT. */"
+  echo "/* Every autoconf define (>= all -D options on the compiler lines). */"
+  echo "#ifndef _MAGIC_AUTOCONF_CONFIG_H"
+  echo "#define _MAGIC_AUTOCONF_CONFIG_H 1"
+  grep '^#define ' confdefs.h | sort -u
+  echo "#endif /* _MAGIC_AUTOCONF_CONFIG_H */"
+} > "$magic_config_header"
+AC_MSG_NOTICE([created config header $magic_config_header])
+
 AC_OUTPUT
 
 dnl