Re: libgpg-error 1.61: t-printf failure on powerpc64-linux

[C. Neidahl via Gnupg-users]

It's also in little-endian, I suppose.

Well, yes and no.





> +# ifdef __powerpc64__
> +  if (verbose)
> +    show ("IBM double-double - skipping LDBL_MAX test\n");



The GCC on my machine, after importing <float.h> with C23 enabled, defines:

#define __LDBL_IS_IEC_60559__ 0
#define LDBL_IS_IEC_60559 __LDBL_IS_IEC_60559__
#define __LONG_DOUBLE_IBM128__ 1





#define __LDBL_IS_IEC_60559__ 1
#define LDBL_IS_IEC_60559 __LDBL_IS_IEC_60559__
#define __LONG_DOUBLE_IEEE128__ 1




diff --git a/tests/t-printf.c b/tests/t-printf.c
index b0a3f3f..79f6470 100644
--- a/tests/t-printf.c
+++ b/tests/t-printf.c
@@ -469,7 +469,13 @@ check_large_float (void)
     show ("format \"%%.100Lf\" with DBL_MAX: ->%s<-\n", buf);
   gpgrt_free (buf);

-# ifdef HAVE_LONG_DOUBLE_WIDER
+# if defined(__powerpc64__) && !LDBL_IS_IEC_60559
+  if (verbose)
+    show ("IBM double-double - skipping LDBL_MAX test\n");
+# elif !defined(HAVE_LONG_DOUBLE_WIDER)
+  if (verbose)
+    show ("LDBL_MAX == DBL_MAX - skipping LDBL_MAX test\n");
+# else
   ld = LDBL_MAX;
   buf = gpgrt_bsprintf ("%.100Lf\n", ld);
   if (buf)
@@ -479,9 +485,6 @@ check_large_float (void)
   else if (verbose)
     show ("format \"%%.100Lf\" with LDBL_MAX failed as expected\n");
   gpgrt_free (buf);
-# else
-  if (verbose)
-    show ("LDBL_MAX == DBL_MAX - skipping LDBL_MAX test\n");
 # endif

 #endif /*HAVE_LO
NG_DOUBLE*/


[0]: https://gcc.gnu.org/onlinedocs/gcc/Floating-Types.html

If usage of the VSX extension is enabled, then an IEEE-compliant 128-bit floating-point type is made available [0]. Glibc can be configured to use that type for long double, and i.e. Fedora has made that switch for its powerpc64le-linux target [1]. powerpc64-linux should be available on systems that predate the VSX extension though, so the default for those is generally still the IBM double-double. For example, the machine that I'm testing things on is an Apple Power Mac G5 from 2005, which lacks both VSX and the option to switch to little-endian mode without bricking the system. As a result of that, powerpc64le-linux is not something that I can test in any way, but I'm still *somewhat* aware of it. I suppose the most exact check for this situation would have to inspect some more LDBL_* defines, otherwise 128-bit IEEE-backed long double would end up not getting checked. LDBL_IS_IEC_60559 of 0 indicates that the long double type does not match an IEC 60559 format (1: format, but not operation; 2: format and operation) [2]. The rest of the floating-point types have their corresponding defines at 1 on my system. By comparison, a powerpc64le-linux GCC cross toolchain on my main system gives: Doesn't seem like Clang itself implements LDBL_IS_IEC_60559, but you use gnulib, which handles that. It sets LDBL_IS_IEC_60559 to 0 with x86_64-linux Clang due to the 80-bit floating-point type, while x86_64-linux GCC sets it to 1 with the same type, so there's some discrepancies on other platforms though... So maybe: [1]: https://fedoraproject.org/wiki/Releases/36/ChangeSet#New_128-bit_IEEE_long_double_ABI_for_IBM_64-bit_POWER_LE [2]: https://github.com/gcc-mirror/gcc/blob/b77cf8f055cce3e42f09410cbbf1e4f1e196b25d/gcc/c-family/c-cppbuiltin.cc#L321-L323

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