From: Jonathan Wakely <jwakely@redhat.com>
Date: Tue, 25 Jun 2019 13:18:36 +0000 (+0100)
Subject: Fix non-portable use of std::abs(double) in constexpr function
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=e88d863cbde6ee90709d291670a843346f84d3b6;p=gcc.git

Fix non-portable use of std::abs(double) in constexpr function

Although libstdc++ adds 'constexpr' to its std::abs(floating-point)
overloads (as a non-conforming extension), those overloads are not used
if the target libc provides them, which is the case on Solaris.

The fix is to avoid std::abs and simply apply the negation when needed.

	* include/std/numeric (midpoint(T, T)): Avoid std::abs in constexpr
	function.

From-SVN: r272653
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d7392553901..7222810984d 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,8 @@
+2019-06-25  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/numeric (midpoint(T, T)): Avoid std::abs in constexpr
+	function.
+
 2019-06-25  Jakub Jelinek  <jakub@redhat.com>
 
 	* include/pstl/pstl_config.h (_PSTL_PRAGMA_SIMD_SCAN,
diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric
index af684469769..2f9462183dd 100644
--- a/libstdc++-v3/include/std/numeric
+++ b/libstdc++-v3/include/std/numeric
@@ -162,7 +162,6 @@ _GLIBCXX_END_NAMESPACE_VERSION
 
 #if __cplusplus > 201703L
 #include <limits>
-#include <bits/std_abs.h>
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -196,11 +195,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{
 	  constexpr _Tp __lo = numeric_limits<_Tp>::min() * 2;
 	  constexpr _Tp __hi = numeric_limits<_Tp>::max() / 2;
-	  if (std::abs(__a) <= __hi && std::abs(__b) <= __hi) [[likely]]
+	  const _Tp __abs_a = __a < 0 ? -__a : __a;
+	  const _Tp __abs_b = __b < 0 ? -__b : __b;
+	  if (__abs_a <= __hi && __abs_b <= __hi) [[likely]]
 	    return (__a + __b) / 2; // always correctly rounded
-	  if (std::abs(__a) < __lo) // not safe to halve __a
+	  if (__abs_a < __lo) // not safe to halve __a
 	    return __a + __b/2;
-	  if (std::abs(__b) < __lo) // not safe to halve __b
+	  if (__abs_b < __lo) // not safe to halve __b
 	    return __a/2 + __b;
 	  return __a/2 + __b/2;	    // otherwise correctly rounded
 	}