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From f7439f9b1089e17b6721f28e228682831a2f0135 Mon Sep 17 00:00:00 2001
From: "Gabriel F. T. Gomes" <gftg@linux.vnet.ibm.com>
Date: Mon, 21 Aug 2017 14:23:27 +0200
Subject: [PATCH] Do not use __builtin_types_compatible_p in C++ mode (bug
21930)
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.
(cherry picked from commit 47a67213a9f51c5f8816d240500b10db605d8b77)
[Romain rebase on glibc 2.26]
Signed-off-by: Romain Naour <romain.naour@gmail.com>
---
math/math.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/math/math.h b/math/math.h
index e217080..dea8dbe 100644
--- a/math/math.h
+++ b/math/math.h
@@ -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))
--
2.9.5
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