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cross-compilation guesses (10)


From: Bruno Haible
Subject: cross-compilation guesses (10)
Date: Wed, 02 May 2012 00:24:54 +0200
User-agent: KMail/4.7.4 (Linux/3.1.10-1.9-desktop; KDE/4.7.4; x86_64; ; )

When cross-compiling, I also see this wrong guess:

  checking for signbit macro... guessing no

This should fix it. (Most of this patch is merely reindentation.)


2012-05-01  Bruno Haible  <address@hidden>

        signbit: Avoid "guessing no" when cross-compiling to glibc systems.
        * m4/signbit.m4 (gl_SIGNBIT): Require AC_CANONICAL_HOST. When cross-
        compiling to a glibc system, set gl_cv_func_signbit to "guessing yes".

--- m4/signbit.m4.orig  Wed May  2 00:22:54 2012
+++ m4/signbit.m4       Wed May  2 00:22:51 2012
@@ -1,4 +1,4 @@
-# signbit.m4 serial 11
+# signbit.m4 serial 12
 dnl Copyright (C) 2007-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,6 +7,7 @@
 AC_DEFUN([gl_SIGNBIT],
 [
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
   AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit],
     [
       AC_RUN_IFELSE(
@@ -27,7 +28,13 @@
 ])],
         [gl_cv_func_signbit=yes],
         [gl_cv_func_signbit=no],
-        [gl_cv_func_signbit="guessing no"])
+        [case "$host_os" in
+                   # Guess yes on glibc systems.
+           *-gnu*) gl_cv_func_signbit="guessing yes" ;;
+                   # If we don't know, assume the worst.
+           *)      gl_cv_func_signbit="guessing no" ;;
+         esac
+        ])
     ])
   dnl GCC 4.0 and newer provides three built-ins for signbit.
   dnl They can be used without warnings, also in C++, regardless of <math.h>.
@@ -50,86 +57,91 @@
 ])],
         [gl_cv_func_signbit_gcc=yes],
         [gl_cv_func_signbit_gcc=no],
-        [gl_cv_func_signbit_gcc="guessing no"])
+        [# If we don't know, assume the worst.
+         gl_cv_func_signbit_gcc="guessing no"
+        ])
     ])
   dnl Use the compiler built-ins whenever possible, because they are more
   dnl efficient than the system library functions (if they exist).
   if test "$gl_cv_func_signbit_gcc" = yes; then
     REPLACE_SIGNBIT_USING_GCC=1
   else
-    if test "$gl_cv_func_signbit" != yes; then
-      dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built.
-      REPLACE_SIGNBIT=1
-      gl_FLOAT_SIGN_LOCATION
-      gl_DOUBLE_SIGN_LOCATION
-      gl_LONG_DOUBLE_SIGN_LOCATION
-      if test "$gl_cv_cc_float_signbit" = unknown; then
-        dnl Test whether copysignf() is declared.
-        AC_CHECK_DECLS([copysignf], , , [[#include <math.h>]])
-        if test "$ac_cv_have_decl_copysignf" = yes; then
-          dnl Test whether copysignf() can be used without libm.
-          AC_CACHE_CHECK([whether copysignf can be used without linking with 
libm],
-            [gl_cv_func_copysignf_no_libm],
-            [
-              AC_LINK_IFELSE(
-                [AC_LANG_PROGRAM(
-                   [[#include <math.h>
-                     float x, y;]],
-                   [[return copysignf (x, y) < 0;]])],
-                [gl_cv_func_copysignf_no_libm=yes],
-                [gl_cv_func_copysignf_no_libm=no])
-            ])
-          if test $gl_cv_func_copysignf_no_libm = yes; then
-            AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1],
-              [Define if the copysignf function is declared in <math.h> and 
available in libc.])
+    case "$gl_cv_func_signbit" in
+      *yes) ;;
+      *)
+        dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built.
+        REPLACE_SIGNBIT=1
+        gl_FLOAT_SIGN_LOCATION
+        gl_DOUBLE_SIGN_LOCATION
+        gl_LONG_DOUBLE_SIGN_LOCATION
+        if test "$gl_cv_cc_float_signbit" = unknown; then
+          dnl Test whether copysignf() is declared.
+          AC_CHECK_DECLS([copysignf], , , [[#include <math.h>]])
+          if test "$ac_cv_have_decl_copysignf" = yes; then
+            dnl Test whether copysignf() can be used without libm.
+            AC_CACHE_CHECK([whether copysignf can be used without linking with 
libm],
+              [gl_cv_func_copysignf_no_libm],
+              [
+                AC_LINK_IFELSE(
+                  [AC_LANG_PROGRAM(
+                     [[#include <math.h>
+                       float x, y;]],
+                     [[return copysignf (x, y) < 0;]])],
+                  [gl_cv_func_copysignf_no_libm=yes],
+                  [gl_cv_func_copysignf_no_libm=no])
+              ])
+            if test $gl_cv_func_copysignf_no_libm = yes; then
+              AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1],
+                [Define if the copysignf function is declared in <math.h> and 
available in libc.])
+            fi
           fi
         fi
-      fi
-      if test "$gl_cv_cc_double_signbit" = unknown; then
-        dnl Test whether copysign() is declared.
-        AC_CHECK_DECLS([copysign], , , [[#include <math.h>]])
-        if test "$ac_cv_have_decl_copysign" = yes; then
-          dnl Test whether copysign() can be used without libm.
-          AC_CACHE_CHECK([whether copysign can be used without linking with 
libm],
-            [gl_cv_func_copysign_no_libm],
-            [
-              AC_LINK_IFELSE(
-                [AC_LANG_PROGRAM(
-                   [[#include <math.h>
-                     double x, y;]],
-                   [[return copysign (x, y) < 0;]])],
-                [gl_cv_func_copysign_no_libm=yes],
-                [gl_cv_func_copysign_no_libm=no])
-            ])
-          if test $gl_cv_func_copysign_no_libm = yes; then
-            AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1],
-              [Define if the copysign function is declared in <math.h> and 
available in libc.])
+        if test "$gl_cv_cc_double_signbit" = unknown; then
+          dnl Test whether copysign() is declared.
+          AC_CHECK_DECLS([copysign], , , [[#include <math.h>]])
+          if test "$ac_cv_have_decl_copysign" = yes; then
+            dnl Test whether copysign() can be used without libm.
+            AC_CACHE_CHECK([whether copysign can be used without linking with 
libm],
+              [gl_cv_func_copysign_no_libm],
+              [
+                AC_LINK_IFELSE(
+                  [AC_LANG_PROGRAM(
+                     [[#include <math.h>
+                       double x, y;]],
+                     [[return copysign (x, y) < 0;]])],
+                  [gl_cv_func_copysign_no_libm=yes],
+                  [gl_cv_func_copysign_no_libm=no])
+              ])
+            if test $gl_cv_func_copysign_no_libm = yes; then
+              AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1],
+                [Define if the copysign function is declared in <math.h> and 
available in libc.])
+            fi
           fi
         fi
-      fi
-      if test "$gl_cv_cc_long_double_signbit" = unknown; then
-        dnl Test whether copysignl() is declared.
-        AC_CHECK_DECLS([copysignl], , , [[#include <math.h>]])
-        if test "$ac_cv_have_decl_copysignl" = yes; then
-          dnl Test whether copysignl() can be used without libm.
-          AC_CACHE_CHECK([whether copysignl can be used without linking with 
libm],
-            [gl_cv_func_copysignl_no_libm],
-            [
-              AC_LINK_IFELSE(
-                [AC_LANG_PROGRAM(
-                   [[#include <math.h>
-                     long double x, y;]],
-                   [[return copysignl (x, y) < 0;]])],
-                [gl_cv_func_copysignl_no_libm=yes],
-                [gl_cv_func_copysignl_no_libm=no])
-            ])
-          if test $gl_cv_func_copysignl_no_libm = yes; then
-            AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1],
-              [Define if the copysignl function is declared in <math.h> and 
available in libc.])
+        if test "$gl_cv_cc_long_double_signbit" = unknown; then
+          dnl Test whether copysignl() is declared.
+          AC_CHECK_DECLS([copysignl], , , [[#include <math.h>]])
+          if test "$ac_cv_have_decl_copysignl" = yes; then
+            dnl Test whether copysignl() can be used without libm.
+            AC_CACHE_CHECK([whether copysignl can be used without linking with 
libm],
+              [gl_cv_func_copysignl_no_libm],
+              [
+                AC_LINK_IFELSE(
+                  [AC_LANG_PROGRAM(
+                     [[#include <math.h>
+                       long double x, y;]],
+                     [[return copysignl (x, y) < 0;]])],
+                  [gl_cv_func_copysignl_no_libm=yes],
+                  [gl_cv_func_copysignl_no_libm=no])
+              ])
+            if test $gl_cv_func_copysignl_no_libm = yes; then
+              AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1],
+                [Define if the copysignl function is declared in <math.h> and 
available in libc.])
+            fi
           fi
         fi
-      fi
-    fi
+        ;;
+    esac
   fi
 ])
 




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