Скачать или смотреть Resolving External Function Call Failure in Inno Setup

Discover how to fix the `External function call failure` issue you might encounter while developing with Inno Setup by using a simple solution.
---
This video is based on the question https://stackoverflow.com/q/74079424/ asked by the user 'Alexander Dyagilev' ( https://stackoverflow.com/u/3765267/ ) and on the answer https://stackoverflow.com/a/74081764/ provided by the user 'Alexander Dyagilev' ( https://stackoverflow.com/u/3765267/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: External function call failure

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Resolving External Function Call Failure in Inno Setup: A Step-by-Step Guide

When creating installers with Inno Setup, developers occasionally encounter hurdles that can disrupt their workflow. One common issue arises when performing actions during uninstall—specifically, an External function call failure. If you've tried to remove a folder to the Recycle Bin using SHFileOperation and encountered strange runtime errors, you’re not alone! In this guide, we will unpack the issue, diagnose its root cause, and provide a straightforward solution.

Understanding the Problem

What is the External Function Call Failure?

The External function call failure typically manifests itself in various forms during uninstallation. In your case, you might see:

Inno Setup 5: Runtime Error (at 2:67): Internal error: An attempt was made to access WizardForm before it has been created.

Inno Setup 6: Runtime error (at 2:82): Could not call proc.

These errors can be confusing and might lead you to question whether you're encountering a bug in Inno Setup or if there’s something amiss in your code.

The Cause of the Issue

Upon close examination, the issue boils down to how you’re assigning the handle for the FileOp structure. In your original code, you assigned the handle using the WizardForm object:

[[See Video to Reveal this Text or Code Snippet]]

This approach works fine when installing. However, during uninstallation, the wizard form may not be initialized, leading to the errors you've encountered.

The Solution

The solution to this issue is surprisingly simple! Instead of assigning the handle to WizardForm.Handle, you will want to set it to 0. This change prevents the code from attempting to access the wizard form when it's not present.

Here’s the correct code snippet:

[[See Video to Reveal this Text or Code Snippet]]

Steps to Implement the Solution

Open Your Inno Setup Script: Start by locating the .iss script where you're defining the uninstallation process.

Adjust the Code: In the procedure for the uninstallation step, replace the line where you set the FileOp.hwnd:

From:

[[See Video to Reveal this Text or Code Snippet]]

To:

[[See Video to Reveal this Text or Code Snippet]]

Test the Changes: Re-run your installation and uninstallation processes to confirm that the changes resolved the External function call failure.

Conclusion

By setting the FileOp.hwnd to 0 during the uninstallation process in Inno Setup, you can circumvent the External function call failure issue. This small, yet significant, adjustment allows the SHFileOperation function to execute correctly without accessing an uninitialized wizard form.

Remember, when debugging installation scripts, it's essential to consider how and when various components of your installer are initialized. Through careful coding practices, you can ensure a smoother user experience. If you have any questions or run into further issues, feel free to reach out!