How to get gdb to work using macports under OSX 10.11 El Capitan?

Question

This arose from How to install gdb (debugger) in Mac OSX El Capitan?.

I have macports working under el capitan no problem and have installed the gdb port but I can\

Answer 1

I installed MacPorts gcc9 (gcc-9.2.0) on an older iMac (10.11.6 El Capitan), and recently needed to install the gdb port (gdb-9.1.0); predictably encountering the same code-signing / permission issue.

There's a list of instructions on github that worked perfectly for me, simply replacing: /usr/local/bin/gdb with: /opt/local/bin/ggdb. Since such snippets on github may be ephemeral, so I'll paste it here:

1. Open Keychain Access
2. In the menu, open Keychain Access > Certificate Assistant > Create a certificate
3. Give it a name (e.g. gdbc)
   • Identity type: Self Signed Root
   • Certificate type: Code Signing
   • Check: let me override defaults
4. Continue until it prompts you for: "specify a location for..."
5. Set Keychain location to System
6. Create a certificate and close assistant.
7. Find the certificate in System keychains, right click it > get info (or just double click it)
8. Expand Trust, set Code signing to always trust
9. Restart taskgated in terminal: killall taskgated
10. Enable root account:
    1. Open System Preferences
    2. Go to User & Groups > Unlock
    3. Login Options > "Join" (next to Network Account Server)
    4. Click "Open Directory Utility"
    5. Go up to Edit > Enable Root User
11. Run codesign -fs gdbc /usr/local/bin/gdb in terminal: this asks for the root password
12. Disable root account (see #10)

Done!