gdb fails with "Unable to find Mach task port for process-id" error

Here is a really useful guide which solved my problem(OSX 10.13.6).

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. Run codesign -fs gdbc /usr/local/bin/gdb in terminal: this asks for the root password

These instructions work for OSX High Sierra and avoid running gdb as root (yuck!). I recently updated from OSX 10.13.2 to 10.3.3. I think this is when gdb 8.0.1 (installed w/ homebrew) started failing for me.

I had difficulty with other people's instructions. After different instructions, everything was a mess. So I started a fresh. I more or less followed these instructions.

Clean the mess :

1. brew uninstall --force gdb # This deletes _all_ versions of gdb on the machine
2. In Applications -> Utilities -> Keychain Access, I deleted all previous gdb certificates and keys (be sure you know what you're doing here!). It's unclear if this is necessary, but since I'd buggered up trying to create those certificates and keys using other instructions I eliminated them anyways. I had keys and certificates in both login and system.

Now reinstall gdb.

3. brew install gdb
4. Within Keychain Access, go to menu Keychain Access-> Certificate Assistant -> Create a Certificate
5. Check "Let me override defaults" and set

Name : gdb-cert
Identity Type: Self Signed Root
Certificate Type : Code Signing

[X] Let me override defaults

6. On 1st Certificate Information page:

Serial Number : 1
Validity Period (days): 3650

7. On 2nd Certificate Information page, I left all fields blank except those already filled in.

8. On Key Pair Information page, I left the defaults

Key Size : 2048
Algorithm : RSA

9. On Key Usage Extension page, I left the defaults checked.

[X] Include Key Usage Extension
[X] This extension is critical
Capabilities:
[X] Signature

10. On Extended Key Usage Extension page, I left the defaults checked.

[X] Include Extended Key Usage Extension
[X] This extension is critical
Capabilities:
[X] Code Signing

11. On Basic Constraints Extension Page, nothing was checked (default).

12. On Subject Alternate Name Extension page, I left the default checked and didn't add anything else.

[X] Include Subject Alternate Name Extension

13. On Specify a Location for the certificate page, I set

Keychain: System

14. I clicked Create and was prompted for my password.

15. Back in the Keychain Access app, I went to System and right clicked on gdb-cert and under dropdown menu Trust, I changed all the fields to Always Trust.

16. Rebooted computer.

17. At the Terminal, I ran codesign -s gdb-cert /usr/local/bin/gdb. I entered my password when prompted.

18. At the Terminal, I ran echo "set startup-with-shell off" >> ~/.gdbinit

19. I ran gdb myprogram and then start within the gdb console. Here, I believe, it prompted for me for my password. After that, all subsequent runs, it did not prompt for my password.