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Delphi, IBX and the Turkish I problem

June 12, 2018, 10:00 pm
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Last year, it took a while to reproduce and it is likely not fixed anytime soon: if you use Delphi and IBX (InterBase Express) to connect to either InterBase or FireBird database, then in the Turkish locale do not use lowercase SQL in your Delphi code as it will break on the

I’ve decided to put this in a separate post than the one I discovered the issue in as that one focused on the Unicode and language background of the various i/I/ characters and this post on the Delphi part.

So for the non-Delphi part, read Source: Field “id” not found and the The Turkish-İ/I/i/ı and case conversion – Update on the dasBlog Turkish-I bug and a reminder to me on Globalization – Scott Hanselman.

In general, this problem is called [WayBack] Case Folding and many environments do not have good and ready to use solutions for this.

Basically when working with case-insensitive language identifiers, you should always use culture invariant text comparison operations. In most languages, people use either lowercase or uppercase converted operations which for Delphi >= come down to using :

The reason is simple:

  • without any parameter, ToLower and ToUpper will use [Archive.is] SysLocale.DefaultLCID.
  • without any parameter, LowerCase and UpperCase will implicitly behave as if called with TLocaleOptions.loInvariantLocale, but lots of people forget they do.

The functions ToLowerInvariant and  ToUpperInvariant  were added in Delphi XE3, but ToLower(LocaleID) and ToUpper(LocaleID) in Delphi XE4.

Instead of doing uppercase and lowercase comparisons you could also use the [Archive.is] System.SysUtils.CompareText function.

IBX however uses case conversion, and by now you will probably guessed it: IBX got it all wrong. One reproduction is at https://gist.github.com/jpluimers/643b382944ff991d07ec96abbf85548c and a thread with background is at [WayBack] What’s the Delphi equivalent of doing UpperCase with an InvariantCulture in Unicode Delphi versions? (XE and up) – Jeroen Wiert Pluimers – Google+

IBX isn’t alone: just search for other uppercase issues like Turkish i to see tons of other issues.

For IBX, I did the replacements in the diff below to fix it in Delphi XE8. I only replaced where identifiers were compared, not were actual database content was compared.

Unluckily, in the past IBX sources were hosted on CodeCentral at http://cc.embarcadero.com/Author/102 but no new bundles have been released since 2012.

Of all the locations I think IBX should not have used any case conversion here:

IBX.IBDatabaseINI.pas – function LocalServerPath(sFile: string): string

This function uses LowerCase() but I think an NTFS specific comparison should have been used, but I’ve not investigated into a solution for that yet.

–jeroen

PS: Potentially related is [WayBack/Archive.is] FireDAC problem with MSSQL: We have an issue using FireDAC on Microsoft SQL Server 2016, in that we have a case sensitive ( not the insensitive default) … – Tony Danby – Google+

PS: To make it easier finding back the archived URLs of the links above, here is a list:

Reproduction: IBDataSetTestsUnit

Diff of the Delphi XE8 IBX sources against the fixed sources

Reproducible case

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