Re: Infinite recusion in test-timespec_getres.exe

[Paul Eggert]

On 12/31/21 04:56, Gisle Vanem wrote:
> Paul Eggert wrote:
>
> > On 12/30/21 07:48, Gisle Vanem wrote:
> > > -#elif defined HAVE_TIMESPEC_GETRES
> > > +#elif defined HAVE_TIMESPEC_GETRES && HAVE_TIMESPEC_GETRES
> >
> > This change has an effect only if there's the equivalent of '#define 
> > HAVE_TIMESPEC_GETRES 0' somewhere. 
>
> Since 'time.in.h' says:
>    #  if ! @HAVE_TIMESPEC_GETRES@
>    _GL_FUNCDECL_SYS (timespec_getres, int, (struct timespec *ts, int base)
> ..
>
> it makes sense to me this should be replaced with a '0' or '1'.

That would make sense, but it's not how it works. Although the shell 
variable and Makefile macro (which is what @HAVE_TIMESPEC_GETRES@ 
expands to) is either 0 or 1, the C preprocessor macro of the same name 
is either 1 or undefined. This is like most other HAVE_ symbols, e.g., 
HAVE_OPENAT.


> Or you mean it should be replaced with
>    defined HAVE_TIMESPEC_GETRES ?

I don't see why anything needs replacing.

Perhaps you configured or built with the compiler option 
'-DHAVE_TIMESPEC_GETRES=0'? If so, don't do that. On the other hand, if 
'./gnulib-tool --test timespec_getres' caused the stack overflow you 
mentioned, without any special compiler options, we need to figure out 
how the HAVE_TIMESPEC_GETRES preprocessor macro was incorrectly #defined 
to 0.


> I fail to understand how the value of 'HAVE_TIMESPEC_GETRES'
> is used by m4 etc.

gnulib-tool creates Makefile snippets that use HAVE_TIMESPEC_GETRES. The 
'time' module replaces @HAVE_TIMESPEC_GETRES@ with 
$(HAVE_TIMESPEC_GETRES) in these snippets. When you then run 
'configure', it replaces @HAVE_TIMESPEC_GETRES@ with 
$(HAVE_TIMESPEC_GETRES) in those snippets, and it also defines the 
Makefile HAVE_TIMESPEC_GETRES macro to be 1 or 0 in the generated 
Makefiles. 'configure' also arranges for '#define HAVE_TIMESPEC_GETRES 
1', or just a comment, to appear in config.h.

$ git grep HAVE_TIMESPEC_GETRES
lib/gettime-res.c:#elif defined HAVE_TIMESPEC_GETRES
lib/time.in.h:#  if ! @HAVE_TIMESPEC_GETRES@
m4/time_h.m4:  HAVE_TIMESPEC_GETRES=1; 
AC_SUBST([HAVE_TIMESPEC_GETRES])
m4/timespec_getres.m4:    HAVE_TIMESPEC_GETRES=0
modules/time:	      -e 
's|@''HAVE_TIMESPEC_GETRES''@|$(HAVE_TIMESPEC_GETRES)|g' \
modules/timespec_getres:gettime-res     [test $HAVE_TIMESPEC_GETRES = 0]
modules/timespec_getres:if test $HAVE_TIMESPEC_GETRES = 0; then