Unable to debug GNT in Windows 10



Stepping on a CALL to a GNT simply runs through. The debugger is unable to step in the GNT or stop at any of the breakpoints in a GNT program.

This problem occurs only in Windows 10, not in any other Windows versions.


Microsoft released a major update for Windows 10 in August or September 2016, which is called the "Windows 10 Anniversary update." This update somehow broke the possibility of debugging GNT programs in Visual COBOL.

To determine if you have the Windows 10 Anniversary update, click the Start button, then click Settings > System > About.

  • If the About window shows Version 1511 (OS Build 10565), it means the Windows 10 Anniversary update is not installed, and debugging GNT should work fine.
  • If the About window shows Version 1607 (OS Build 14393), it means the Windows 10 Anniversary update was already installed, and debugging GNT does not work.

Microsoft will release another major update of Windows 10 in spring of 2017, and we were unable to recreate the problem with the preview build starting with 14931.

In the meantime, you might want to consider one of the following alternatives:

  • remove Windows 10 Anniversary update
  • compile the GNT to DLL
  • use another machine running one of the supported environments (e.g. Windows 7, Windows 8.1, Windows Server 2012, etc.)

It is not recommended to install the preview build of Windows 10 as it is still on a test phase.

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