In NC, it is "duty to inform." The twisted part is that if one os pulled over, the cop already knows. NC ties CCH permits to DMV records. So, no matter what state I'm in, if I got pulled over, the trooper already knows.
In NC, if the first words out of my mouth are not "I have a permit, I have a gun and is on my hip at the 8:00 position, I could lose my permit.
Only criminals do not have to inform as requiring a criminal to tell a police officer that they have a gun would be a violation of the 5th amendment.
Another problem is that informing gives the officer immediate justification to draw and shoot. Trigger happy cops without body cam, obstructed cruiser cam. "I thought he was reaching for the gun (he was required by law to tell me he had).
One guy wrote about how his wife got pulled over. She complied with the law, told the cop she was armed. The a-hole stepped back, put his hand on his side arm and says "you are going to shoot me are you?"