From a8b4c93ccd8ff8e1aadf89325f9cef7d3b8278a4 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Wed, 17 Jan 2018 13:27:57 +1100
Subject: [PATCH] coord: mitigate gcc ICE when using redim

---
 coord/base.hpp | 48 ++++++++++++++++++++++++++++++++----------------
 test/point.cpp |  3 +--
 2 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/coord/base.hpp b/coord/base.hpp
index 41c370d6..52dd0ccd 100644
--- a/coord/base.hpp
+++ b/coord/base.hpp
@@ -148,21 +148,24 @@ namespace util::coord {
         ///
         /// explicitly does not allow a fill parameter given it can't be used
         /// when reducing dimensions.
+        ///
+        /// HACK,gcc#,gcc-7.x: This function _must not_ use std::copy or
+        /// similar algorithms to move the data as it produces an ICE on some
+        /// code fragements if it does. Namely:
+        ///   "internal compiler error: in trunc_int_for_mode, at explow.c:55"
         template <
             size_t D,
-            typename _sfinae = SelfT
-        >
-        std::enable_if_t<
-            has_redim_v<_sfinae>,
-            redim_t<_sfinae,D>
+            typename = std::enable_if_t<
+                has_redim_v<SelfT> && S >= D,
+                void
+            >
         >
+        auto
         redim (void) const
         {
             redim_t<SelfT,D> out;
-
-            std::copy_n (std::cbegin (this->data),
-                         min (S, D),
-                         std::begin  (out.data));
+            for (size_t i = 0; i < D; ++i)
+                out[i] = this->data[i];
             return out;
         }
 
@@ -174,17 +177,24 @@ namespace util::coord {
         ///
         /// explicitly requires a fill parameter so that we avoid undefined
         /// values.
+        ///
+        /// HACK,gcc#,gcc-7.x: This function _must not_ use std::copy or
+        /// similar algorithms to move the data as it produces an ICE on some
+        /// code fragements if it does. Namely:
+        ///   "internal compiler error: in trunc_int_for_mode, at explow.c:55"
         template<size_t D,typename _sfinae = SelfT>
         std::enable_if_t<
-            has_redim_v<_sfinae>,
+            has_redim_v<_sfinae> && S <= D,
             redim_t<_sfinae,D>
         >
         redim (const redim_t<_sfinae,D> fill) const
         {
             redim_t<SelfT,D> out;
 
-            auto next = std::copy (cbegin (), cend (), std::begin (out));
-            std::copy (std::cbegin (fill) + S, std::cend (fill), next);
+            for (size_t i = 0; i < S; ++i)
+                out[i] = this->data[i];
+            for (size_t i = S; i < D; ++i)
+                out[i] = fill[i];
             return out;
         }
 
@@ -194,20 +204,26 @@ namespace util::coord {
         ///
         /// explicitly requires a fill parameter so that we avoid undefined
         /// values.
+        ///
+        /// HACK,gcc#,gcc-7.x: This function _must not_ use std::copy or
+        /// similar algorithms to move the data as it produces an ICE on some
+        /// code fragements if it does. Namely:
+        ///   "internal compiler error: in trunc_int_for_mode, at explow.c:55"
         template <
             size_t D,
             typename _sfinae = SelfT
         >
         std::enable_if_t<
-            has_redim_v<_sfinae>,
+            has_redim_v<_sfinae> && S <= D,
             redim_t<_sfinae,D>
         >
         redim (T fill) const
         {
             redim_t<SelfT,D> out;
-
-            auto next = std::copy (cbegin (), cend (), std::begin (out));
-            std::fill (next, std::end (out), fill);
+            for (size_t i = 0; i < S; ++i)
+                out[i] = this->data[i];
+            for (size_t i = S; i < D; ++i)
+                out[i] = fill;
             return out;
         }
 
diff --git a/test/point.cpp b/test/point.cpp
index 14261df6..d63559df 100644
--- a/test/point.cpp
+++ b/test/point.cpp
@@ -20,6 +20,7 @@ main (void)
         const point2f r { 0.f, 1.f };
 
         tap.expect_eq (q, r, "redim to lower dimension");
+
     }
 
     // Redim to higher dimension without fill
@@ -39,7 +40,6 @@ main (void)
     //
     // HACK: This fails under GCC-7.1.0, and i'm not wasting any more time
     // reducing this test case. it's _really_ template heavy.
-#if !(__GNUC_PREREQ (7, 1))
     {
         static const point4f FILL (1.f, 2.f, 3.f, 4.f);
         const point2f p (0.1f, 1.f);
@@ -54,7 +54,6 @@ main (void)
             "redim to higher with fill"
         );
     }
-#endif
 
     // Simple linking check for coord type casting. Relies on truncation.
     {