From 883d2ad4d2d689463f028b6be0b268f3683b1ff2 Mon Sep 17 00:00:00 2001
From: Puck Meerburg <puck@puckipedia.com>
Date: Sun, 17 Mar 2024 16:04:36 +0000
Subject: [PATCH] libexpr: use std::function rather than C function pointers
 for primops

In preparation for the C bindings, which use this.

Change-Id: Ic1c58998951e69e66a794976585a381754dfbbeb
---
 src/libexpr/eval.hh    | 2 +-
 src/libexpr/primops.cc | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 135e5fecb..2e3c73157 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -36,7 +36,7 @@ enum RepairFlag : bool;
 /**
  * Function that implements a primop.
  */
-typedef void (* PrimOpFun) (EvalState & state, const PosIdx pos, Value * * args, Value & v);
+typedef std::function<void (EvalState &, const PosIdx, Value **, Value &)> PrimOpFun;
 
 /**
  * Info about a primitive operation, and its implementation
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 86db527f6..236afb554 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3279,8 +3279,11 @@ static void prim_sort(EvalState & state, const PosIdx pos, Value * * args, Value
            callFunction. */
         /* TODO: (layus) this is absurd. An optimisation like this
            should be outside the lambda creation */
-        if (args[0]->isPrimOp() && args[0]->primOp->fun == prim_lessThan)
-            return CompareValues(state, noPos, "while evaluating the ordering function passed to builtins.sort")(a, b);
+        if (args[0]->isPrimOp()) {
+            auto target = args[0]->primOp->fun.target<decltype(&prim_lessThan)>();
+            if (target && *target == prim_lessThan)
+                return CompareValues(state, noPos, "while evaluating the ordering function passed to builtins.sort")(a, b);
+        }
 
         Value * vs[] = {a, b};
         Value vBool;