Use std::strong_ordering for version comparison

The actual motive here is the avoidance of integer overflow if we were
to make these use checked NixInts and retain the subtraction.

However, the actual *intent* of this code is a three-way comparison,
which can be done with operator<=>, so we should just do *that* instead.

Change-Id: I7f9a7da1f3176424b528af6d1b4f1591e4ab26bf

1 files changed, 2 insertions, 1 deletions

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 72ae1aeb9..80c64232f 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -4162,7 +4162,8 @@ static void prim_compareVersions(EvalState & state, const PosIdx pos, Value * *
 {
     auto version1 = state.forceStringNoCtx(*args[0], pos, "while evaluating the first argument passed to builtins.compareVersions");
     auto version2 = state.forceStringNoCtx(*args[1], pos, "while evaluating the second argument passed to builtins.compareVersions");
-    v.mkInt(compareVersions(version1, version2));
+    auto result = compareVersions(version1, version2);
+    v.mkInt(result < 0 ? -1 : result > 0 ? 1 : 0);
 }
 
 static RegisterPrimOp primop_compareVersions({