[1/3] Do not use __builtin_types_compatible_p in C++ mode (bug 21930)
Commit Message
The logic to define isinf for float128 depends on the availability of
__builtin_types_compatible_p, which is only available in C mode,
however, the conditionals do not check for C or C++ mode. This lead to
an error in libstdc++ configure, as reported by bug 21930.
This patch adds a conditional for C mode in the definition of isinf for
float128. No definition is provided in C++ mode, since libstdc++
headers undefine isinf.
Tested for powerpc64le (glibc test suite and libstdc++-v3 configure).
[BZ #21930]
* math/math.h (isinf): Check if in C or C++ mode before using
__builtin_types_compatible_p, since this is a C mode feature.
---
math/math.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Comments
On Tue, 15 Aug 2017, Gabriel F. T. Gomes wrote:
> The logic to define isinf for float128 depends on the availability of
> __builtin_types_compatible_p, which is only available in C mode,
> however, the conditionals do not check for C or C++ mode. This lead to
> an error in libstdc++ configure, as reported by bug 21930.
>
> This patch adds a conditional for C mode in the definition of isinf for
> float128. No definition is provided in C++ mode, since libstdc++
> headers undefine isinf.
OK.
On Tue, 15 Aug 2017 19:56:44 +0000
Joseph Myers <joseph@codesourcery.com> wrote:
> On Tue, 15 Aug 2017, Gabriel F. T. Gomes wrote:
>
> > The logic to define isinf for float128 depends on the availability of
> > __builtin_types_compatible_p, which is only available in C mode,
> > however, the conditionals do not check for C or C++ mode. This lead to
> > an error in libstdc++ configure, as reported by bug 21930.
> >
> > This patch adds a conditional for C mode in the definition of isinf for
> > float128. No definition is provided in C++ mode, since libstdc++
> > headers undefine isinf.
>
> OK.
>
Thanks. I pushed patches 1 and 3 in this thread. Patch 2 still needs
more changes.
@@ -442,8 +442,12 @@ enum
/* Return nonzero value if X is positive or negative infinity. */
# if __HAVE_DISTINCT_FLOAT128 && !__GNUC_PREREQ (7,0) \
- && !defined __SUPPORT_SNAN__
- /* __builtin_isinf_sign is broken for float128 only before GCC 7.0. */
+ && !defined __SUPPORT_SNAN__ && !defined __cplusplus
+ /* Since __builtin_isinf_sign is broken for float128 before GCC 7.0,
+ use the helper function, __isinff128, with older compilers. This is
+ only provided for C mode, because in C++ mode, GCC has no support
+ for __builtin_types_compatible_p (and when in C++ mode, this macro is
+ not used anyway, because libstdc++ headers undefine it). */
# define isinf(x) \
(__builtin_types_compatible_p (__typeof (x), _Float128) \
? __isinff128 (x) : __builtin_isinf_sign (x))