Paul Eggert wrote:
> On your host, 64-bit signed preprocessor numbers work,
> but the unsigned ones don't.
Yes, it looks like this, assuming that the autoconf tests are correct.
> Can you please try this code:
>
> #if ! (18446744073709551615ULL <= -1u)
> error in preprocessor;
> #endif
>
> and tell me what diagnostics (if any) your compiler generates?
>
> Perhaps the simplest workaround is to change the above test to something like
> this:
>
> #if ! (18446744073709551614ULL <= 18446744073709551615ULL)
> error in preprocessor;
> #endif
Indeed, the result depends on the precise condition:
$ cat > foo.c
#if ! (18446744073709551615ULL <= -1u)
error in preprocessor;
#endif
$ cc -Ae -O -c foo.c
cc: "foo.c", line 2: error 1000: Unexpected symbol: "in".
cc: "foo.c", line 2: warning 557: Missing declaration specifiers, "int" assumed.
$ cat > foo.c
#if ! (18446744073709551615ULL <= -1ull)
error in preprocessor;
#endif
$ cc -Ae -O -c foo.c
cc: "foo.c", line 1: warning 501: Empty source file.
$ cat > foo.c
#if ! (-9223372036854775807LL < 0 && 0 < 9223372036854775807ll)
error in preprocessor;
#endif
$ cc -Ae -O -c foo.c
cc: "foo.c", line 1: warning 501: Empty source file.
$ cat > foo.c
#if ! (18446744073709551614ULL <= 18446744073709551615ULL)
error in preprocessor;
#endif
$ cc -Ae -O -c foo.c
cc: "foo.c", line 1: warning 501: Empty source file.
$ cat > foo.c
#if ! (18446744073709551615ULL <= 18446744073709551615ULL)
error in preprocessor;
#endif
$ cc -Ae -O -c foo.c
cc: "foo.c", line 1: warning 501: Empty source file.
As you can see, all tests pass except the one that uses -1u. Whereas the
one with -1ull works.
Quite explainable:
18446744073709551615ULL is 0xFFFFFFFFFFFFFFFFULL
-1u is 0xFFFFFFFFU
so you end up comparing
0xFFFFFFFFFFFFFFFFULL against 0x00000000FFFFFFFFULL
therefore I find it quite natural that this test fails.
I propose this fix (in gnulib, similarly for autoconf):
2007-10-22 Bruno Haible <[EMAIL PROTECTED]>
* m4/ulonglong.m4 (AC_TYPE_UNSIGNED_LONG_LONG_INT): Use -1ull, not
-1u, in preprocessor expression.
--- m4/ulonglong.m4.orig 2007-10-22 13:00:48.000000000 +0200
+++ m4/ulonglong.m4 2007-10-22 13:00:16.000000000 +0200
@@ -1,4 +1,4 @@
-# ulonglong.m4 serial 7
+# ulonglong.m4 serial 8
dnl Copyright (C) 1999-2007 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -21,7 +21,7 @@
[ac_cv_type_unsigned_long_long_int],
[AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
- [[#if ! (18446744073709551615ULL <= -1u)
+ [[#if ! (18446744073709551615ULL <= -1ull)
error in preprocessor;
#endif
unsigned long long int ull = 18446744073709551615ULL;
