[libcxx] [llvm] [libc++][math][c++17] P0226R1 - Mathematical Special Functions: infra + `std::assoc_laguerre` (PR #205649)

[via llvm-commits]

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+# Local libc++ patch for the vendored Boost.Math snapshot.
+#
+# Boost.Math only uses <sstream>/<iomanip> and detail::prec_format to build the
+# what() text of the exceptions it throws. That machinery sits OUTSIDE Boost's own
+# `#ifndef BOOST_MATH_NO_EXCEPTIONS` guard (unlike the adjacent <stdexcept> /
+# throw_exception.hpp includes), so it is compiled even when exceptions are disabled.
+# libc++ builds the Math Special Functions back-end with BOOST_MATH_NO_EXCEPTIONS,
+# and on configurations without localization (e.g. -DLIBCXX_ENABLE_LOCALIZATION=OFF)
+# libc++ ships no functional <sstream>, so prec_format fails to compile.
+#
+# This patch guards the iostream-only message formatting under BOOST_MATH_NO_EXCEPTIONS.
+# Reported upstream: https://github.com/boostorg/math/issues/1412
+# Re-applied by update_boost_math.sh after each snapshot refresh; drop once upstream.
+diff --git a/boost-math/include/boost/math/policies/error_handling.hpp b/boost-math/include/boost/math/policies/error_handling.hpp
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PaulXiCao wrote:

Makes sense! Just created a pr for this: #223166 .

https://github.com/llvm/llvm-project/pull/205649