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On a Mac, you may encounter the following error when using gdb for the first time:

(gdb) run
Starting program: /usr/local/bin/order_monitor
Unable to find Mach task port for process-id 26551: (os/kern) failure (0x5).
(please check gdb is codesigned - see taskgated(8))

This is because the Darwin kernel does not allow debugging other processes without special permissions. Debugging a process means that you have full control over the process, so it is disabled by default to prevent malicious use. The best way to allow gdb to control other processes is to sign it with a certificate that the system trusts.

Create a certificate

Follow these steps to create a code signing certificate:

1. Open the Keychain Access application
2. Go to menu Keychain Access -> Certificate Assistant -> Create Certificate
3. Fill in the following information:
   • Name: gdb_codesign (you can customize other names)
   • Identity Type: Self-signed root certificate
   • Certificate Type: Code Signing
   • Check: Let me override these defaults
4. Continue until you reach the step to specify the certificate location and select System
5. Click "Create" and you will be prompted for the data system login password, and the creation is complete. (Note: If you select the system in the fourth step , the creation may fail. At this time, you can choose to log in in the fourth step to create it. After the creation is successful, just drag the newly created certificate directly into the system on the left . If you can create it directly by selecting the system , ignore this note)
6. In the Keychain Access program, select System and My Certificates in the left column, find the gdb_codesign certificate you just created , double-click it to open the certificate information window, expand the Trust item, and set When using this certificate : Always trust .
7. Close the certificate information window and the system will ask you to enter the system login password again.

Sign gdb

Execute the following command

 codesign -fs gdb_codesign(上面创建的证书名称) $(which gdb)

Note: The above signing command is for Mac systems before version 10.14 (Mojave). If our system is after 10.14 (Mojave), we need to create a file gdb-entitlement.xml first , the content is as follows:

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
<key>com.apple.security.cs.debugger</key>
   <true/>
</dict>
</plist>
</pre>

Then execute

codesign --entitlements gdb-entitlement.xml -fs gdb_codesign $(which gdb)

After completion, be sure to restart the system, otherwise the signature will not take effect.

Solve the problem of gdb debugging failure

After the above operation, the gdb signature problem is solved. However, sometimes you may encounter the following problems.

(gdb) run
Starting program: /usr/local/bin/order_monitor
During startup program terminated with signal ?, Unknown signal.

The solution is very simple, just execute the following command

set startup-with-shell off

For convenience, this command can be written to the .gdbinit file in your personal directory.