Use a nicely written autoconf macro to determine the sign of a type

This beats our old implementation, which wouldn't work when cross-compiling

5 files changed, 68 insertions, 22 deletions

diff --git a/Makefile.am b/Makefile.am
index 2854763d2..4639c22c4 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -7,6 +7,8 @@
 # 1.9 means we require automake vesion 1.9
 AUTOMAKE_OPTIONS = foreign 1.9 subdir-objects
 
+ACLOCAL_AMFLAGS = -I m4
+
 noinst_LIBRARIES=
 EXTRA_DIST=
 noinst_HEADERS=
diff --git a/autogen.sh b/autogen.sh
index efa2251c2..8c43a9798 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -17,7 +17,7 @@ fi
 set -e
 
 # Run this to generate all the initial makefiles, etc.
-aclocal && \
+aclocal -I m4 && \
 	autoheader && \
 	autoconf && \
 	automake --add-missing --copy
diff --git a/changes/signof_enum b/changes/signof_enum
new file mode 100644
index 000000000..fc9b9eda2
--- /dev/null
+++ b/changes/signof_enum
@@ -0,0 +1,4 @@
+  o Code simplifications and refactoring:
+    - Use Ville Laurikari's implementation of AX_CHECK_SIGN() to determine
+      the signs of types during autoconf. This is better than our old
+      approach, which didn't work when cross-compiling.
diff --git a/configure.ac b/configure.ac
index c27cbd2c8..e80e6f612 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5,6 +5,7 @@ dnl See LICENSE for licensing information
 
 AC_INIT([tor],[0.2.4.10-alpha-dev])
 AC_CONFIG_SRCDIR([src/or/main.c])
+AC_CONFIG_MACRO_DIR([m4])
 AM_INIT_AUTOMAKE
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 AC_CONFIG_HEADERS([orconfig.h])
@@ -957,8 +958,9 @@ AC_CHECK_TYPES([rlim_t], , ,
 #endif
 ])
 
-AC_CACHE_CHECK([whether time_t is signed], tor_cv_time_t_signed, [
-AC_RUN_IFELSE([AC_LANG_SOURCE([
+AX_CHECK_SIGN([time_t],
+       [ AC_DEFINE(TIME_T_IS_SIGNED, 1, [Define if time_t is signed]) ],
+       [ : ], [
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
@@ -968,32 +970,16 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([
 #ifdef HAVE_TIME_H
 #include <time.h>
 #endif
-int main(int c, char**v) { if (((time_t)-1)<0) return 1; else return 0; }])],
-  tor_cv_time_t_signed=no, tor_cv_time_t_signed=yes, tor_cv_time_t_signed=cross)
 ])
 
-if test "$tor_cv_time_t_signed" = cross; then
-  AC_MSG_NOTICE([Cross compiling: assuming that time_t is signed.])
-fi
-
-if test "$tor_cv_time_t_signed" != no; then
-  AC_DEFINE([TIME_T_IS_SIGNED], 1,
-            [Define to 1 iff time_t is signed])
-fi
-
-AC_CACHE_CHECK([whether size_t is signed], tor_cv_size_t_signed, [
-AC_RUN_IFELSE([AC_LANG_SOURCE([
+AX_CHECK_SIGN([size_t],
+       [ tor_cv_size_t_signed=yes ],
+       [ tor_cv_size_t_signed=no ], [
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
-int main(int c, char**v) { if (((size_t)-1)<0) return 1; else return 0; }])],
-  tor_cv_size_t_signed=no, tor_cv_size_t_signed=yes, tor_cv_size_t_signed=cross)
 ])
 
-if test "$tor_cv_size_t_signed" = cross; then
-  AC_MSG_NOTICE([Cross compiling: assuming that size_t is not signed.])
-fi
-
 if test "$tor_cv_size_t_signed" = yes; then
   AC_MSG_ERROR([You have a signed size_t; that's grossly nonconformant.])
 fi
diff --git a/m4/ax_check_sign.m4 b/m4/ax_check_sign.m4
new file mode 100644
index 000000000..104b17014
--- /dev/null
+++ b/m4/ax_check_sign.m4
@@ -0,0 +1,54 @@
+# ===========================================================================
+#       http://www.gnu.org/software/autoconf-archive/ax_check_sign.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_SIGN (TYPE, [ACTION-IF-SIGNED], [ACTION-IF-UNSIGNED], [INCLUDES])
+#
+# DESCRIPTION
+#
+#   Checks whether TYPE is signed or not. If no INCLUDES are specified, the
+#   default includes are used. If ACTION-IF-SIGNED is given, it is
+#   additional shell code to execute when the type is signed. If
+#   ACTION-IF-UNSIGNED is given, it is executed when the type is unsigned.
+#
+#   This macro assumes that the type exists. Therefore the existence of the
+#   type should be checked before calling this macro. For example:
+#
+#     AC_CHECK_HEADERS([wchar.h])
+#     AC_CHECK_TYPE([wchar_t],,[ AC_MSG_ERROR([Type wchar_t not found.]) ])
+#     AX_CHECK_SIGN([wchar_t],
+#       [ AC_DEFINE(WCHAR_T_SIGNED, 1, [Define if wchar_t is signed]) ],
+#       [ AC_DEFINE(WCHAR_T_UNSIGNED, 1, [Define if wchar_t is unsigned]) ], [
+#     #ifdef HAVE_WCHAR_H
+#     #include <wchar.h>
+#     #endif
+#     ])
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Ville Laurikari <vl@iki.fi>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 6
+
+AU_ALIAS([VL_CHECK_SIGN], [AX_CHECK_SIGN])
+AC_DEFUN([AX_CHECK_SIGN], [
+ typename=`echo $1 | sed "s/@<:@^a-zA-Z0-9_@:>@/_/g"`
+ AC_CACHE_CHECK([whether $1 is signed], ax_cv_decl_${typename}_signed, [
+   AC_TRY_COMPILE([$4],
+     [ int foo @<:@ 1 - 2 * !((($1) -1) < 0) @:>@ ],
+     [ eval "ax_cv_decl_${typename}_signed=\"yes\"" ],
+     [ eval "ax_cv_decl_${typename}_signed=\"no\"" ])])
+ symbolname=`echo $1 | sed "s/@<:@^a-zA-Z0-9_@:>@/_/g" | tr "a-z" "A-Z"`
+ if eval "test \"\${ax_cv_decl_${typename}_signed}\" = \"yes\""; then
+   $2
+ elif eval "test \"\${ax_cv_decl_${typename}_signed}\" = \"no\""; then
+   $3
+ fi
+])dnl