"No source available for main()" error when debugging simple C++ in Eclipse with gdb

This thread suggests:

-g -O0

for debug flags to be set for Eclipse CDT compilation.
Sometime, it is simple a problem of rebuilding completely the application (like here)

See also this thread describing a similar situation:

I have noticed that sometimes in Eclipse I have to go and specifically add the path to my source files using the "add filesystem path" (with "search sub-folders") in the Debug Dialog (even when they are in the same project I am debugging), but I have not noticed a pattern to when I have to do this. But it may be worth a try.

I found the answer! And it's embarrassingly simple.

The problem was that I was using the Release version of SDL instead of the Debug version! (I had 'libsdl' from MacPorts whereas I should have had 'libsdl-devel'.)

So my generic answer is: make sure the libs you're linking against were compiled with debug flags set too, it's not always enough to just make sure your own code has them set.

Here is another reason for this problem. My configuration used -g3 as the option to gcc. Changing it to -g solved the problem. There seems to be some incompatibility between gcc and gdb. I checked that gdb was the latest revision (using apt-get).