From f536696b732bc81c0aa05e20ff0e37dd0d02a2d4 Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Fri, 8 Mar 2024 07:48:31 +0100
Subject: [PATCH] Add comments

(cherry picked from commit 474fc4078acbe062fcc31ce91c69c8f33bf00d5f)
Change-Id: I9f78f7afd8468d0ab676c0f60c4f7d6140128583
---
 src/libexpr/eval-error.cc |  2 +-
 src/libexpr/eval-error.hh | 30 ++++++++----------------------
 2 files changed, 9 insertions(+), 23 deletions(-)

diff --git a/src/libexpr/eval-error.cc b/src/libexpr/eval-error.cc
index b9411cbf4..250c59a19 100644
--- a/src/libexpr/eval-error.cc
+++ b/src/libexpr/eval-error.cc
@@ -91,7 +91,7 @@ void EvalErrorBuilder<T>::debugThrow()
 
     // `EvalState` is the only class that can construct an `EvalErrorBuilder`,
     // and it does so in dynamic storage. This is the final method called on
-    // any such instancve and must delete itself before throwing the underlying
+    // any such instance and must delete itself before throwing the underlying
     // error.
     auto error = std::move(this->error);
     delete this;
diff --git a/src/libexpr/eval-error.hh b/src/libexpr/eval-error.hh
index 1faf76781..e9076f28b 100644
--- a/src/libexpr/eval-error.hh
+++ b/src/libexpr/eval-error.hh
@@ -57,6 +57,11 @@ public:
     }
 };
 
+/**
+ * `EvalErrorBuilder`s may only be constructed by `EvalState`. The `debugThrow`
+ * method must be the final method in any such `EvalErrorBuilder` usage, and it
+ * handles deleting the object.
+ */
 template<class T>
 class EvalErrorBuilder final
 {
@@ -91,29 +96,10 @@ public:
     [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> &
     addTrace(PosIdx pos, std::string_view formatString, const Args &... formatArgs);
 
+    /**
+     * Delete the `EvalErrorBuilder` and throw the underlying exception.
+     */
     [[gnu::noinline, gnu::noreturn]] void debugThrow();
 };
 
-/**
- * The size needed to allocate any `EvalErrorBuilder<T>`.
- *
- * The list of classes here needs to be kept in sync with the list of `template
- * class` declarations in `eval-error.cc`.
- *
- * This is used by `EvalState` to preallocate a buffer of sufficient size for
- * any `EvalErrorBuilder<T>` to avoid allocating while evaluating Nix code.
- */
-constexpr size_t EVAL_ERROR_BUILDER_SIZE = std::max({
-    sizeof(EvalErrorBuilder<EvalError>),
-    sizeof(EvalErrorBuilder<AssertionError>),
-    sizeof(EvalErrorBuilder<ThrownError>),
-    sizeof(EvalErrorBuilder<Abort>),
-    sizeof(EvalErrorBuilder<TypeError>),
-    sizeof(EvalErrorBuilder<UndefinedVarError>),
-    sizeof(EvalErrorBuilder<MissingArgumentError>),
-    sizeof(EvalErrorBuilder<InfiniteRecursionError>),
-    sizeof(EvalErrorBuilder<CachedEvalError>),
-    sizeof(EvalErrorBuilder<InvalidPathError>),
-});
-
 }