From 33f54cf4f81a51e5c8cbfb2408edd439bdee9435 Mon Sep 17 00:00:00 2001 From: "Gabriel F. T. Gomes" Date: Wed, 20 Sep 2017 15:10:26 -0300 Subject: [PATCH] Let fpclassify use the builtin when optimizing for size in C++ mode (bug 22146) When optimization for size is on (-Os), fpclassify does not use the type-generic __builtin_fpclassify builtin, instead it uses __MATH_TG. However, when library support for float128 is available, __MATH_TG uses __builtin_types_compatible_p, which is not available in C++ mode. On the other hand, libstdc++ undefines (in cmath) many macros from math.h, including fpclassify, so that it can provide its own functions. However, during its configure tests, libstdc++ just tests for the availability of the macros (it does not undefine them, nor does it provide its own functions). Finally, when libstdc++ is configured with optimization for size enabled, its configure tests include math.h and get the definition of fpclassify that uses __MATH_TG (and __builtin_types_compatible_p). Since libstdc++ does not undefine the macros during its configure tests, they fail. This patch lets fpclassify use the builtin in C++ mode, even when optimization for size is on. This allows the configure test in libstdc++ to work. Tested for powerpc64le and x86_64. [BZ #22146] math/math.h: Let fpclassify use the builtin in C++ mode, even when optimazing for size. (cherry picked from commit c5c4a626098ec884b8527356abdf2a4bb7b6bf27) [Romain rebase on glibc 2.26) Signed-off-by: Romain Naour --- math/math.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/math/math.h b/math/math.h index 7c0fc6d..f9348ec 100644 --- a/math/math.h +++ b/math/math.h @@ -402,7 +402,13 @@ enum /* Return number of classification appropriate for X. */ # if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__ \ - && !defined __OPTIMIZE_SIZE__ + && (!defined __OPTIMIZE_SIZE__ || defined __cplusplus) + /* The check for __cplusplus allows the use of the builtin, even + when optimization for size is on. This is provided for + libstdc++, only to let its configure test work when it is built + with -Os. No further use of this definition of fpclassify is + expected in C++ mode, since libstdc++ provides its own version + of fpclassify in cmath (which undefines fpclassify). */ # define fpclassify(x) __builtin_fpclassify (FP_NAN, FP_INFINITE, \ FP_NORMAL, FP_SUBNORMAL, FP_ZERO, x) # else -- 2.9.5