Hello Forum,

I have an build issue and I don't know how to solve it.

I have an big project with many libs and files. It targets the wemos d1 mini pro / lite (esp2866 chip).
If I build it in visual micro, this error appears:

stdio.h:6: In file included from
stdio.h:63: from
cstdio:42: from
random:39: from
stl_algo.h:65: from
algorithm:62: from
WiFiClientSecureBearSSL.cpp:27: from
pgmspace.h: In function uint32_t pgm_read_dword_unaligned(const void*)
pgmspace.h: 121:1: error: a15 cannot be used in asm here

This is a known error in the esp2866 community for some time and one fix was to downgrade the board definition, but this was not very helpful because then I got trouble with some libs. 

But this is not why I am here. 
If I build the same ino file in Arduino IDE, then all works very well.
I have checked all build options, that they are the same in VM and in Arduino ide. I've tried all build optimization settings, rescanned toolchains, uninstalled and reinstalled libs, switch between "visual micro (no die)" and "arduino 1.6/1.8". I deleted temp folders everywhere I could find them.
Also easy example-projects in VisualMicro build very well.
I also create a new project and moved all files there to get rid of possible old configs in the project file, but the error still occures. And I rebooted my PC several times.


This is driving me crazy. I have no idea what else I could investigate or try.
Have you an Ideas why both ideas behave so different on the same code? I mean they won't use different compilers, or?

I haven't used this project for like 6 months and so I don't remember possible changes in the last time. But i know that the building worked last time I used this project on my old PC. Now I am on a new PC and I installed all "fresh".
On my old PC it works like a charm. So the issue must be at the visual micro instance at this specific pc.

I really hope you can help me with some ideas.

Attached is the verbose build output.

Best regards, Tobi.

VisualMicro Version new PC: 2021.106.0
VisualMicro Version old PC: 2020.910.8
Windows 10 20H2
Visual Stuio new PC: 2019 16.8.4
Visual Stuio old PC: 2019 16.8.1

Hi and thanks for the answere.

Yes I saw this post and have tried every Optimisation and did not achive something.

However. I tried it now again after reverted several git version back and forth and revertet libs and boards and now it works. 
I am a bit shocked and don't understand why it works. But besides that I am very thankfull that you said the right thing at the right moment.

It works now just with the defaul Optimisation. 
Why it works also with no Optimisation at my old pc probably remains a mystery.

Best regards, Tobi