gcc -O2 is smaller then gcc -O2 -g followed by strip --strip-all

Question

I am building code that I want to produce release versions. However I also want to be able to debug cores if they crash.

So I read that building with debug symbols can be used followed by producing a copy of the binary that you run strip on. Then you can take the core produced by the stripped binary (the released/customer binary) and then gdb this against your copy of the binary with debug symbols...

So step one for me was to generate the binary, I do:

• gcc -O2 ... -o testbin_release_orig (original release bin without symbols)
• gcc -O2 -g ... -o testbin_debug (full debug binary)
• cp testbin_debug testbin_release
• strip --strip-all testbin_release (stripped debug binary)

This produces three files with different sizes:

• testbin_release_orig: ~1.7Mb
• testbin_debug: ~13Mb
• testbin_release: ~2.1Mb

My question is, why is testbin_release not exactly the same size as testbin_release_orig ? I am guessing that strip can't strip all the debug symbols that gcc adds. But there is about 0.4Mb of "extra stuff" - what does that consist of?

Answer 1

The difference is from the debug code.

For an 1.7 MB executable you are probably using a library or two. Usually they have something like:

#ifdef _DEBUG
    // some debug code
#endif

Also common practice for big projects, so some of it may be your code as well.

strip removes only the symbols. The debug code stays.