[adding bug-autoconf]
On 06/13/2010 05:43 PM, Bruno Haible wrote:
> Hi Ben,
>
>> The problem is that AC_FUNC_STRTOD assumes that strtod does not
>> exist when cross-compiling, which in turn makes the strtod module
>> assume that it does not need to handle an existing declaration.
>
> Ah, so AC_FUNC_STRTOD makes gnulib think that strtod() does not exist,
> although in fact it does exist. Just because of the worst-case guess
> that says "ac_cv_func_strtod=no".
>
> - When we are cross-compiling, we should avoid pessimistic guesses
> such as "ac_cv_func_strtod=no". The reason is that the most frequent
> use of cross-compiling is done for embedded Linux devices (devices
> with BusyBox, or everything-on-a-chip systems). In such cases,
> it is not well seen if gnulib provides a replacement function when
> in fact it is not needed at all. So, please, when cross-compiling,
> give a thought to the embedded Linux case (with glibc or uClibc).
>
> So: Do current embedded Linuxes have the strtod bugs or not? Take a
> look at the AC_FUNC_STRTOD macro in autoconf/lib/autoconf/functions.m4:
>
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1537)#
> AC_FUNC_STRTOD
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1538)#
> --------------
> 7134f17d (Akim Demaille 2002-09-28 14:06:07 +0000
> 1539)AN_FUNCTION([strtod], [AC_FUNC_STRTOD])
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000
> 1540)AC_DEFUN([AC_FUNC_STRTOD],
> 1492d7c5 (Akim Demaille 2001-11-12 15:47:35 +0000
> 1541)[AC_SUBST(POW_LIB)dnl
> 1492d7c5 (Akim Demaille 2001-11-12 15:47:35 +0000
> 1542)AC_CACHE_CHECK(for working strtod, ac_cv_func_strtod,
> 6a2a74c2 (Akim Demaille 2001-07-04 14:37:52 +0000
> 1543)[AC_RUN_IFELSE([AC_LANG_SOURCE([[
> 11ee0ab5 (Paul Eggert 2004-05-03 20:15:44 +0000
> 1544)]AC_INCLUDES_DEFAULT[
> 11ee0ab5 (Paul Eggert 2004-05-03 20:15:44 +0000 1545)#ifndef
> strtod
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1546)double
> strtod ();
> 11ee0ab5 (Paul Eggert 2004-05-03 20:15:44 +0000 1547)#endif
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1548)int
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1549)main()
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1550){
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1551) {
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1552) /*
> Some versions of Linux strtod mis-parse strings with leading '+'. */
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1553) char
> *string = " +69";
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1554) char
> *term;
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1555)
> double value;
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1556)
> value = strtod (string, &term);
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1557) if
> (value != 69 || term != (string + 4))
> a71c24a7 (Paul Eggert 2006-04-03 03:18:39 +0000 1558)
> return 1;
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1559) }
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1560)
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1561) {
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1562) /*
> Under Solaris 2.4, strtod returns the wrong value for the
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1563)
> terminating character under some conditions. */
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1564) char
> *string = "NaN";
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1565) char
> *term;
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1566)
> strtod (string, &term);
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1567) if
> (term != string && *(term - 1) == 0)
> a71c24a7 (Paul Eggert 2006-04-03 03:18:39 +0000 1568)
> return 1;
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1569) }
> a71c24a7 (Paul Eggert 2006-04-03 03:18:39 +0000 1570) return
> 0;
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1571)}
> 6a2a74c2 (Akim Demaille 2001-07-04 14:37:52 +0000 1572)]])],
> b44e483c (Akim Demaille 2003-05-17 10:30:07 +0000 1573)
> ac_cv_func_strtod=yes,
> b44e483c (Akim Demaille 2003-05-17 10:30:07 +0000 1574)
> ac_cv_func_strtod=no,
> b44e483c (Akim Demaille 2003-05-17 10:30:07 +0000 1575)
> ac_cv_func_strtod=no)])
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1576)if test
> $ac_cv_func_strtod = no; then
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1577)
> _AC_LIBOBJ_STRTOD
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1578)fi
> 7bd04c77 (Akim Demaille 2000-08-01 11:16:33 +0000 1579)])
>
> With two old old old tests and no reasonable cross-compiling behaviour I
> would say that the best thing to do is to move these two blocks of C code
> into gl_FUNC_STRTOD's test, and stop using AC_FUNC_STRTOD. Then the
> autoconf documentation can mark this macro obsolescent, and on the gnulib
> side this test runs one program, not two, and we have full control over
> the cross-compilation behaviour.
Or even better, why not push those two tests upstream into autoconf,
then have gnulib override AC_FUNC_STRTOD if it detects older autoconf,
so that everyone using upstream AC_FUNC_STRTOD can reliably detect these
same bugs?
> @@ -28,6 +34,24 @@
> }
> ]], [[
> {
> + /* In some old versions of Linux (2000 or before), strtod mis-parses
> + strings with leading '+'. */
> + const char *string = " +69";
> + char *term;
> + double value = strtod (string, &term);
> + if (value != 69 || term != (string + 4))
> + return 1;
> + }
> + {
> + /* Under Solaris 2.4, strtod returns the wrong value for the
> + terminating character under some conditions. */
> + const char *string = "NaN";
> + char *term;
> + strtod (string, &term);
> + if (term != string && *(term - 1) == 0)
> + return 1;
> + }
> + {
> /* Older glibc and Cygwin mis-parse "-0x". */
> const char *string = "-0x";
> char *term;
>
>
>
--
Eric Blake ebl...@redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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