This patch addresses some issues in RAD Studio 12.1, around the new editor split view feature of the IDE, the Delphi 64-bit compiler when building packages, debugging, and strings.
Installation via GetIt
If you download the patch via GetIt, it is installed automatically, creating a backup of the files replaced and a log of the operations. However, because PAServer is installed on remote computers, you need to manually reinstall PAServer on each of the target platforms you are working with, following the steps at:

https://docwiki.embarcadero.com/RADStudio/en/Installing_the_Platform_Assistant_on_Windows

https://docwiki.embarcadero.com/RADStudio/Athens/en/Installing_the_Platform_Assistant_on_a_Mac

https://docwiki.embarcadero.com/RADStudio/Athens/en/Installing_the_Platform_Assistant_on_Linux

Manual Download and Installation
This patch is also available in the download portal at my.embarcadero.com. In this case, after downloading and expanding the ZIP file, you should run the patch.R121.patch1_install.bat file or manually expand the R121.patch1.zip into the respective subfolders of the RAD Studio installation folder. You also need to update PAServer on target platforms as discussed above.
Uninstallation Steps
If you installed the patch via GetIt:
* Open the Catalog Repository installation folder and move to the patch folder
* Run the patch.R121.patch1_uninstall.bat file
* Only *after* you have cleared the patch, uninstall the package from GetIt
If you installed the patch manually:
* Open the folder you expanded the patch ZIP file into
* Run the patch.R121.patch1_uninstall.bat file
* Delete the folder and patch ZIP file
Notice on Delphi Win64 Packages
This patch modifies the symbols exported by Delphi packages built for the Windows 64 platform, to address a problem introduced in 12.1. Packages that include unit names with a single underscore character or that refer to units with single underscore character in other packages and built with the RTM version of 12.1 can conflict with unit names using the dot notation. We addressed this issue in the patch, but the net effect is that using packages built with the RTM version of 12.1 might have compatibility issues with the code built after applying this patch. We recommend any third party vendor or developer to update the binary of Delphi Win64 packages built with 12.1 with a version built with this patch applied. This is not required for Delphi Win64 packages built with 12.0. In fact, the compiler in this patch offers improved compatibility with the 12.0 compiler.
Publicly Reported Issues Addresses by This Patch
These issues have been reported in the new quality portal, see this blog post for details on how to create an account, with the exception of the last one, which is in the on the old portal (still available in read-only mode):
RSS-574 [dcc32 Fatal Error] PythonFmx.dpk(70): Internal Error: AV00B5992F-R0000014C-0
RSS-536 Delphi 64-bit DPK compilation problem
RSS-497 F2084 Internal Error: NI5166
RSS-447 F2084 Internal Error: compiling Win64 Package
RSS-425 Error F2084: Interner Fehler: AV006A992F-R0000014C-0
RSS-391 String with non-ASCII characters directly attached to a #xx or #$xx literal corrupts the final string
RSP-40084 StringTable and LoadStr
In addition, this patch addresses two beta reports (not publicly accessible at this time):
- Division by zero when clicking "Move Designer" after Editor split
- Crash in rtl290.bpl when assigning an action to a TPopupMenu via object inspector
The patch also addresses other duplicate issues and the following internally found issues:
- iOS: Can't Run application without Debugging (Ctrl+Shift+F9)
- macOS: Cannot evaluate Edit1.Text + 'abc'
- Split Code Editor: Closing the additional right editor switches the left editor to the Design tab
- Split Code Editor: issue with selecting editor tabs through the menu
- Split Code Editor: AV in IDE if creating a new project after using a split code editor.
- Editor tab group title bar draws incorrectly
RAD Studiois the fastest way to develop cross-platform native apps with flexible cloud services and broad IoT connectivity using Delphi or C++. RAD Studio provides powerful VCL controls for Windows 10 and enables FMX development for Windows, Mac and Mobile. RAD Studio supports Delphi or C++ with a wide array of services for Enterprise Strong Development.
Behind the Build: RAD Studio and C++Builder 12.0 - David Millington
C++Builder 12 brings some massive improvements. We'd like to give you a look behind the scenes and a preview of what's coming. Expect to see in-development tech, an exciting, unfiltered, behind-the-scenes look at what's coming soon in two major areas: the new Clang toolchain, with massive improvements across the RTL, STL, linker, debugger, and more; and the Visual Assist integration, providing navigation, search, and refactoring for C++.
Embarcadero Technologies, Inc.builds tools that solve productivity problems for application developers. The company's products allow users to design, build, and run applications from a single code base across all platforms. Ninety of the Fortune 100 companies and a community of more than three million C++ and Delphi users worldwide rely on Embarcadero's award-winning products to deliver critical enterprise applications. Embarcadero is a division of Idera, Inc.