Return within an unnamed macro: erratic behavior, regression wrt ROOT 5.34

[ferdymercury]

Check duplicate issues.

• Checked for duplicates

Description

See https://root-forum.cern.ch/t/return-from-an-unnamed-macro-in-root-6-broken/29867

Was a subpart of https://its.cern.ch/jira/browse/ROOT-4780

Return behavior was working well with ROOT 5.34 unnamed macros.

Workaround for ROOT6 is obvious, using named macros, but that prevents global variable reuse later from prompt (unless you brutally put all variable declarations outside the named macro upfront)

Reproducer

Run it via root test.cxx

{
  cout << "phase 1" << endl;
  return;
  cout << "phase 2" << endl;

  TChain c;
  cout << "phase3" << endl;

  cout << "end of the program" << endl;
}

You get:

phase 1
phase3
end of the program

It seems as if TChain c is kind of "restarting" the program flow (invalidating the return).

Funnily, it works fine if you copy-paste that snippet into the command prompt, and you just get as expected:

phase 1

ROOT version

ROOT v6.36.02
Built for linuxx8664gcc on Jul 08 2025, 22:08:50
From tags/v6-36-02@v6-36-02
With c++ (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Binary directory: /opt/root/bin

Installation method

Binary release

Operating system

Ubuntu 22.04

Additional context

Same issue with

    ------------------------------------------------------------------
  | Welcome to ROOT 6.39.01                        https://root.cern |
  | (c) 1995-2025, The ROOT Team; conception: R. Brun, F. Rademakers |
  | Built for linuxx8664gcc on Nov 15 2025, 17:33:58                 |
  | From heads/master@v6-23-01-RF-binSampling-25184-g9167c40c2a      |
  | With g++ (Ubuntu 11.4.0-1ubuntu1~22.04.2) 11.4.0 std201703       |
  | Try '.help'/'.?', '.demo', '.license', '.credits', '.quit'/'.q'  |
   ------------------------------------------------------------------