If you wish to compile for debugging, you should use GCC. After
running configure but before running make, edit the
Makefile and remove the -O2 flag from the definition of
CFLAGS. Optionally, do the same for support/Makefile and/or
extensions/Makefile.
Then run make.
You can enable additional debugging code by creating a file
named .developing in the gawk source code directory
before running configure. Doing so enables additional
conditionally-compiled debugging code within gawk, and adds
additional warning and debugging options if compiling with GCC.
It also disables optimization.