Project build failed: Build failed

I’m working in this project, I’m getting an error in the word “strlen”, but i don’t know why, i try compile the project and a message appears “Project build failed: Build failed” like appear in the image, can someone help me?

Hello,

Please can you make picture of your Output and Problems windows?
I do not trust the underlined error on strlen is real issue. How I remember KeilStudio and MbedStudio had an issue with Clang and it marks every function from STD library like “Use of undeclared identifier”.

image

BR, Jan