If, for example, I create a program containing only a main.cpp

int main(void) {
  return 0;
}

and then try to export to GCC ARM Embedded for target FRDM-K64F, the status line goes to "Downloading file..." and then immediately to "Ready" but without downloading anything.

The same happens if I choose a different target (Nucleo F207ZG).

The same happens if I add the mbed-os library.

I do get a download if I instead add the mbed library.

I do get a download if I choose a different toolchain (Keil uVision, Kinetis Design Studio, IAR, emblocks, zipfile)

If I choose GCC (Code Sourcery), the status line changes to "Downloading file..." but then nothing further happens (no download, no "Ready".

GCC Code Sourcery should be removed from the online IDE (we do not release mbed sdk lib to it anymore) - at least for newer mbed SDK releases (I cant recall since when it was deprecated).

What's the mbed lib revision you have been testing exporting with?

Exporting works with mbed revisions 122 and 123.

Exporting fails with mbed-os revisions 2240 and 2242.

Exporting fails if neither mbed nor mbed-os is present.