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

Question

I'm having trouble debugging a C++ program in Eclipse (the latest RC of Helios, updated with latest CDT from within itself) on OSX.

The program is very simple (esentially Lesson 2 from NeHe's OpenGL tutorials), consisting of one cpp file and, using OpenGL and Cocoa frameworks, and linking with libSDL.a and libSDLmain.a.

The structure of the project is very simple: the source file(s) are in a subdirectory of the project called src/ and the executable is built to the project's root directory.

The problem is that whenever I try to add breakpoints and debug it, the breakpoints seem to get hit perfectly but no source is displayed - instead I just get a "No source available for main()" error in the code window.

The compiler flags have optimisations set to none, and both the compiler and linker have the debug symbols flag set (-g).

The debugging setting in Eclipse is set to "Standard spawn progess" and the debugger is set to "gdb".

Now the strangest thing is that if I try to debug the exact same executable - ie. the exact same one that was built by Eclipse - using gdb from the Terminal (shell) then everything works fine. Breakpoints are hit, source code is displayed, no problems at all.

I've made sure that both Eclipse and the shell are using the same gdb executable, and they are (it's /usr/bin/gdb).

Now I may be wrong, but this all suggests to me that there can't be a problem with the compiler and linker flags (because the same executable is debuggable from the shell), so presumably the problem must be with how gdb is being invoked from within Eclipse? Perhaps when run from Eclipse gdb is picking up different config files or something than when it's run from the shell? (Anyone know?)

I'd really appreciate any help with this because it's slowly driving me loopy!

Please let me know if there are any other details that would be useful - exact version numbers of Eclipse/cdt/gdb, exact linker/compiler command lines, etc. - and I'll very gladly update this post with them.

Many thanks in advance,

thoughton.

--- edited @ "14 hours ago" ---

I tried the "add filesystem path" (with "search sub-folders") option, but that didn't work. I also tried creating a new completely flat project, but that didn't work either. I even tried getting a Galileo release (eclipse-SDK-3.5.2RC4 with CDT update), but that made no difference (apart from gdb being slower to launch).

And here's something else strange I noticed: once I get the "No source available" message, if I then switch Eclipse's Console to display the "gdb" console, and also turn on "Verbose console mode" so I can communicate it, I can then issue "l" and "bt" commands and have them work succesfully, showing the correct source and stack where my breakpoint was hit. Which, correct me if I'm wrong, must mean that the information is there and gdb is being invoked correctly - so why will Eclipse not see this information?

I'm getting close to giving up on Eclipse to be honest... I came to it with such high hopes, too.

Any additional help or thoughts would be hugely appreciated.

t.

Answer 1

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.

Answer 2

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.