libexpr: pass Exprs as references, not pointers

almost all places where Exprs are passed as pointers expect the pointers
to be non-null. pass them as references to encode this constraint in the
type system as well (and also communicate that Exprs must not be freed).

Change-Id: Ia98f166fec3c23151f906e13acb4a0954a5980a2

1 files changed, 5 insertions, 5 deletions

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index dba56c011..720ab1a3f 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -244,9 +244,9 @@ static void import(EvalState & state, const PosIdx pos, Value & vPath, Value * v
             // args[0]->attrs is already sorted.
 
             debug("evaluating file '%1%'", path);
-            Expr * e = state.parseExprFromFile(resolveExprPath(path), staticEnv);
+            Expr & e = state.parseExprFromFile(resolveExprPath(path), staticEnv);
 
-            e->eval(state, *env, v);
+            e.eval(state, *env, v);
         }
     }
 }
@@ -390,13 +390,13 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
     auto output = runProgram(program, true, commandArgs);
     Expr * parsed;
     try {
-        parsed = state.parseExprFromString(std::move(output), state.rootPath(CanonPath::root));
+        parsed = &state.parseExprFromString(std::move(output), state.rootPath(CanonPath::root));
     } catch (Error & e) {
         e.addTrace(state.positions[pos], "while parsing the output from '%1%'", program);
         throw;
     }
     try {
-        state.eval(parsed, v);
+        state.eval(*parsed, v);
     } catch (Error & e) {
         e.addTrace(state.positions[pos], "while evaluating the output from '%1%'", program);
         throw;
@@ -4494,7 +4494,7 @@ void EvalState::createBaseEnv()
         // the parser needs two NUL bytes as terminators; one of them
         // is implied by being a C string.
         "\0";
-    eval(parse(code, sizeof(code), derivationInternal, {CanonPath::root}, staticBaseEnv), *vDerivation);
+    eval(*parse(code, sizeof(code), derivationInternal, {CanonPath::root}, staticBaseEnv), *vDerivation);
 }