The runtime's tracing all sits inside #ifdef DEBUG, and nothing has been
defining DEBUG since the configure rewrite, so DEBUG=ALL has silently
produced nothing at all.
Three things were wrong. configure defaulted debug off, where the old
configure.in had it on unless --enable-optimised was given. --enable-debug
only added -g -O0 and never defined DEBUG, so the option did not work
either. And Makefile-common resets CFLAGS, so the flag cannot travel that
way - the template already had the right hook, DDEBUG=@DBGFLAG@, but
DBGFLAG was never substituted.
Now on by default, --enable-optimised to opt out. A run of test 671 that
previously gave no diagnostic at all now writes 450K of trace and names
the failing bind directly.
