libexpr: Consolidate implementation between Value string constructors

Change-Id: I5bf8d58b534cd652d89f7b93019378b66a6a6964

lix/libexpr/value.cc

@@ -2,6 +2,7 @@
 
 #include <ostream>
 
+#include "libexpr/gc-alloc.hh"
 #include "lix/libexpr/eval.hh"
 #include "lix/libexpr/print.hh"
 
@@ -27,15 +28,18 @@ static_assert(alignof(Value::PrimOp) >= Value::Acb::TAG_ALIGN);
 static_assert(alignof(Value::Int) >= Value::Acb::TAG_ALIGN);
 static_assert(alignof(Value::Lambda) >= Value::Acb::TAG_ALIGN);
 
-static void copyContextToValue(Value::String & s, const NixStringContext & context)
+static char const ** copyContext(const NixStringContext & context)
 {
-    if (!context.empty()) {
-        size_t n = 0;
-        s.context = gcAllocType<char const *>(context.size() + 1);
-        for (auto & i : context)
-            s.context[n++] = gcCopyStringIfNeeded(i.to_string());
-        s.context[n] = 0;
+    if (context.empty()) {
+        return nullptr;
     }
+    auto contextPtr = gcAllocType<char const *>(context.size() + 1);
+    size_t n = 0;
+    for (auto & i : context) {
+        contextPtr[n++] = gcCopyStringIfNeeded(i.to_string());
+    }
+    contextPtr[n] = nullptr;
+    return contextPtr;
 }
 
 Value::Value(attrs_t, BindingsBuilder & bindings) : Value(NewValueAs::attrs, bindings.finish()) {}
@@ -62,11 +66,13 @@ void Value::mkPrimOp(PrimOp * p)
 }
 
 Value::Value(string_t, Str * s, const NixStringContext & context)
+    : Value(NewValueAs::string, s, copyContext(context))
+{
+}
+
+Value::Value(string_t, std::string_view s, const NixStringContext & context)
+    : Value(NewValueAs::string, s, copyContext(context))
 {
-    auto block = gcAllocType<String>();
-    *block = {.content = s, .context = nullptr};
-    raw = tag(tString, block);
-    copyContextToValue(*block, context);
 }
 
 #ifndef __APPLE__

lix/libexpr/value.hh

@@ -475,29 +475,7 @@ public:
     ///
     /// The string data *is* copied from @ref copyFrom, and this constructor
     /// performs a dynamic (GC) allocation to do so.
-    Value(string_t, std::string_view copyFrom, NixStringContext const & context = {})
-    {
-        auto block = gcAllocType<String>();
-        *block = {.content = Str::gcCopy(copyFrom), .context = nullptr};
-        raw = tag(tString, block);
-
-        if (context.empty()) {
-            // It stays nullptr.
-            return;
-        }
-
-        // Copy the context.
-        block->context = gcAllocType<char const *>(context.size() + 1);
-
-        size_t n = 0;
-        for (NixStringContextElem const & contextElem : context) {
-            block->context[n] = gcCopyStringIfNeeded(contextElem.to_string());
-            n += 1;
-        }
-
-        // Terminator sentinel.
-        block->context[n] = nullptr;
-    }
+    Value(string_t, std::string_view copyFrom, NixStringContext const & context = {});
 
     /// Constructs a nix language value of type "path", with the value of the
     /// C-string pointed to by @ref strPtr.