Hide FunctionCallTrace constructor/destructor

This prevents them from being inlined. On gcc 9, this reduces the
stack size needed for

  nix-instantiate '<nixpkgs>' -A texlive.combined.scheme-full --dry-run

from 12.9 MiB to 4.8 MiB.

1 files changed, 2 insertions, 12 deletions

diff --git a/src/libexpr/function-trace.hh b/src/libexpr/function-trace.hh
index 2c39b7430..472f2045e 100644
--- a/src/libexpr/function-trace.hh
+++ b/src/libexpr/function-trace.hh
@@ -9,17 +9,7 @@ namespace nix {
 struct FunctionCallTrace
 {
     const Pos & pos;
-
-    FunctionCallTrace(const Pos & pos) : pos(pos) {
-        auto duration = std::chrono::high_resolution_clock::now().time_since_epoch();
-        auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
-        printMsg(lvlInfo, "function-trace entered %1% at %2%", pos, ns.count());
-    }
-
-    ~FunctionCallTrace() {
-        auto duration = std::chrono::high_resolution_clock::now().time_since_epoch();
-        auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(duration);
-        printMsg(lvlInfo, "function-trace exited %1% at %2%", pos, ns.count());
-    }
+    FunctionCallTrace(const Pos & pos);
+    ~FunctionCallTrace();
 };
 }