C++ builder EAccessViolation when calling Variant.OlePropertySet() for Excel Automation

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After migrating an application from C++ Builder 4 to C++builder 6, the excel COM automation started to crash with error EAccessViolation at address 00000800 when calling the Variant.OlePropertySet(), OlePropertyGet() or OleFunction() methods, as in the following code :

[code lang=cpp]
Variant xlApp = Variant::CreateObject(“Excel.Application”);
xlApp.OlePropertySet(“Visible”, true); // causes the EAccessViolation
Variant workbooks = xlApp.OlePropertyGet(“Workbooks”);
Variant currentWorkbook ClasseurCourant = workbooks.OleFunction(“Open”, L”C:\\MyExcelFile.xls”);
[/code]
Excel-OlePropertySet-EAccessViolation
This code was working fine with Builder 4, it was also working fine when used in a brand new application, but it always crashed in the converted app. Given that many developers reported the same error, with no known fix, and that one couldn’t expect support for a 12 years old IDE, I eventually fixed the issue by bypassing the Borland Wrappers and using directly COM.
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Wattpad API requests must contain a valid browser User-Agent header

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Recently, I’ve been playing with the Wattpad API. I was interested in collecting stats about the most popular publications.
Wattpad_logo_svg
Even though the API is simple and well documented, all attempts to use it through a python script failed. Requests were rejected with a “403 Access forbidden” HTTP error. My first intuition was that the basic authentication was incorrectly specified, but despite the API samples, I couldn’t figure out what was wrong with it.

Using WireShark to sniff the API sample requests would have helped solving the issue, but since the API only supports https, sniffing wasn’t an option (I later realized that I could have simply disabled https, just to sniff the request, since I didn’t care about the response).

Eventually, the problem came from the User-Agent header. The python script used a default User-Agent, which was rejected by the Wattpad server. Impersonating a legitimate browser (ex : chrome) solved the issue, requests were immediately accepted.

Below is a Python sample.
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How to execute the same SQL query on each database of a SQL Server instance ?

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You want to execute the same SQL query on each database of your SQL Server. For example, because you have one database per customer and want to collect info about your customers’ databases version, size, etc.

The following T-SQL code illustrates how to get the number of tables in each database whose name starts with “RH”, and presents the result in one single recordset. Continue reading →

When should you rewrite an application from scratch ?

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Recently, I had to work on an old C++ builder 4 (1998) application. The IDE couldn’t be installed anymore on Windows 7, there were global variables and singletons everywhere, client-based compilation directives, no separation between UI, business logic and data layer, no class isolation, memory leaks all over the place, compiler failure as soon as the source code got too big, dependencies on obsolete COM objects, etc. A nightmare. It looked like the perfect example of an application that should be rewritten from scratch, and it made me wonder when is it a good time to completely rewrite a product ?

Short answer : Never.
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