cmsHeader causes segmentation violation using ROOT v6.40 #77

ROOT Version: 6.40.00
Built for linuxx8664gcc on May 22 2026, 18:02:23
From tags/6-40-00@6-40-00

Python 3.14.5

uv pip show cmsstyle
Using Python 3.14.5 environment at: ...
Name: cmsstyle
Version: 0.5.0
Location: ...
Requires: typing-extensions
Required-by:

#!/usr/bin/env python3
import cmsstyle as cms
import ROOT as rt


def fixed_cmsHeader(
    leg,
    legTitle,
    textAlign=12,
    textSize=0.04,
    textFont=42,
    textColor=rt.kBlack,
    isToRemove=True,
):
    header = rt.TLegendEntry(0, legTitle, "h")
    header.SetTextFont(textFont)
    header.SetTextSize(textSize)
    header.SetTextAlign(textAlign)
    header.SetTextColor(textColor)
    if isToRemove:
        leg.SetHeader(legTitle, "C")
        leg.GetListOfPrimitives().Remove(leg.GetListOfPrimitives().At(0))
        leg.GetListOfPrimitives().AddAt(header, 0)
    else:
        leg.GetListOfPrimitives().AddLast(header)
    rt.SetOwnership(
        header, False
    )  # This otherwise gets garbage collected as of ROOT 6.40 and python 3.14

def show_with_legend(header_text, header_func):
    canvas = cms.cmsCanvas("canvas", 0, 1, 0, 1, "x", "y")
    leg = cms.cmsLeg(0.2, 0.2, 0.8, 0.8)

    header_func(leg, header_text)
    canvas.Update()
    canvas.Draw()

def run_reproducer():

    show_with_legend("Test header text", fixed_cmsHeader)
    input("A working canvas with a header is now visible. Press return to trigger crash")

    print(
        "Attempting to paint the canvas with a cmsHeader triggers segv.\n"
        "Python garbage collection is at the same time already freeing the header."
    )
    show_with_legend("Broken header text", cms.cmsHeader)
    input("Version not affected. Press return to exit.")

run_reproducer()