[gcc r9-8347] Add 'noexcept' to std::lerp

[Jonathan Wakely]

https://gcc.gnu.org/g:494166791ea6b669f17cf3fbb037000396018420

commit r9-8347-g494166791ea6b669f17cf3fbb037000396018420
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Mar 5 16:52:19 2020 +0000

    Add 'noexcept' to std::lerp
    
    Backport from mainline
    2019-06-17  Jonathan Wakely  <jwakely@redhat.com>
    
    	* include/c_global/cmath (__lerp, lerp): Add noexcept (LWG 3201).

Diff:
---
 libstdc++-v3/ChangeLog              | 5 +++++
 libstdc++-v3/include/c_global/cmath | 8 ++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d5eb49b..0b91af9 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,6 +1,11 @@
 2020-03-05  Jonathan Wakely  <jwakely@redhat.com>
 
 	Backport from mainline
+	2019-06-17  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/c_global/cmath (__lerp, lerp): Add noexcept (LWG 3201).
+
+	Backport from mainline
 	2019-11-07  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/stl_algo.h (for_each_n): Handle negative count.
diff --git a/libstdc++-v3/include/c_global/cmath b/libstdc++-v3/include/c_global/cmath
index b843c18..01e56a5 100644
--- a/libstdc++-v3/include/c_global/cmath
+++ b/libstdc++-v3/include/c_global/cmath
@@ -1891,7 +1891,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   template<typename _Fp>
     constexpr _Fp
-    __lerp(_Fp __a, _Fp __b, _Fp __t)
+    __lerp(_Fp __a, _Fp __b, _Fp __t) noexcept
     {
       if (__a <= 0 && __b >= 0 || __a >= 0 && __b <= 0)
 	return __t * __b + (1 - __t) * __a;
@@ -1908,15 +1908,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     }
 
   constexpr float
-  lerp(float __a, float __b, float __t)
+  lerp(float __a, float __b, float __t) noexcept
   { return std::__lerp(__a, __b, __t); }
 
   constexpr double
-  lerp(double __a, double __b, double __t)
+  lerp(double __a, double __b, double __t) noexcept
   { return std::__lerp(__a, __b, __t); }
 
   constexpr long double
-  lerp(long double __a, long double __b, long double __t)
+  lerp(long double __a, long double __b, long double __t) noexcept
   { return std::__lerp(__a, __b, __t); }
 #endif // C++20