Hi,
This looks like an issue with mbed itself rather than VisualGDB. It could be caused by a buggy platform definition, incompatible settings, or unsupported combination of tools. Please try building the project manually using mbed-cli and check if the problem persists.
You can extract the command line used by VisualGDB by locating the build command line in the VisualGDB Build window (shown in cyan), right-clicking on it and selecting “Dump to a batch file”.
If the project builds manually, but doesn’t build under VisualGDB, please let us know and we will help you configure VisualGDB to match the results of the manual build.