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Missing Implementation for __FlashStringHelper related String functions #439
Description
Prerequisites
Can you reproduce the problem reliably?
Yes, undefined reference errors are thrown when trying to use the SimpleSerialShell.h library
Did you check current release notes for known issues?
If this is not the latest release, have you checked newer releases?
I've checked with the latest 3.5.5 Version
Description:
A clear and concise description of what the bug is.
When registering new commands using the F() Macro using SimpleSerialShell.h, the compiler throws undefined reference errors related to the string library. Looking at the source code of WString.h and WString.cpp in the XMC Core it looks like the declaration for the following functions exist in the header but there is no actual implementation:
- String & String::copy(const __FlashStringHelper *pstr, unsigned int length)
- String &String::operator=(const __FlashStringHelper *str)
- String::String(const __FlashStringHelper *pstr)
The compiler issues can be resolved by copying the implementation from the AVR Core, however I have not tested if the code works with this as of yet.
Steps to Reproduce:
- Install SimpleSerialShell.h and try to configure custom functions
Expected Result:
No Compiler Error 😃
Actual Result:
Compiler Error 🥲
Frequency (1/1, 1/50, 1/100):
1/1
Build/Commit:
3.5.5
Target:
XMC1100 Boot Kit
Host OS and Version:
Windows
Compiler:
Include the version!
Environment
Provide the context surrounding this problem. Perhaps an IDE, a debug probe, an RTOS, etc. (and versions)
Activity
cores: Add missing __FlashStringHelper String implementations.
cores/WString: Add missing __FlashStringHelper implementations.
cores/WString: Add missing __FlashStringHelper implementations.
cores/WString: Add missing __FlashStringHelper implementations.
jaenrig-ifx commentedon Jun 11, 2026
Hi @MaxIfx,
Did you try the latest version 4.x? ->https://github.com/Infineon/XMC-for-Arduino/releases/tag/4.1.1
These functions should be supported in that version.
Any reasons to stay with 3.x?
cores/WString: Add missing __FlashStringHelper implementations.
MaxIfx commentedon Jun 11, 2026
Hi @jaenrig-ifx,
3.5.5 is the latest Version that is shown in my Board Manager so I guess the paths are not up to date in the installation. Thanks for updating the Files!
jaenrig-ifx commentedon Jun 11, 2026
You'll have to update the Additional Boards Manager URL with:
See docs.
ederjc commentedon Jun 18, 2026
Hi @MaxIfx!
As Juan mentioned please update to the latest 4.x release by updating the link in your Arduino IDE.
If you need to work with 3.x for a reason we have also added the missing FlashStringHelper implementation in #441. This was released in https://github.com/Infineon/XMC-for-Arduino/releases/tag/3.5.7.
Best regards
Julian