Re: single-threaded optimizations

[Paul Eggert]

On 3/7/21 1:58 AM, Bruno Haible wrote:
> The mbrtowc modules states:
>
>    Link:
>    $(LIB_MBRTOWC)

Thanks for explaining that. Over time Gnulib has evolved and 'tar' 
hadn't caught up with all those Link: lines. So I just now added 
$(LIB_ACL), $(LIB_GETRANDOM), $(LIB_HARD_LOCALE), $(LIB_HAS_ACL), 
$(LIB_MBRTOWC), and $(LIB_SETLOCALE_NULL) to the tar linking instructions.

However, I have a new problem now. Even though 'tar' now defines 
GNULIB_EXCLUDE_SINGLE_THREAD, GNULIB_MBRTOWC_SINGLE_THREAD, 
GNULIB_REGEX_SINGLE_THREAD, and GNULIB_WCHAR_SINGLE_LOCALE, 'configure' 
still unnecessarily arranges for GNU Tar to be linked with -lpthread, 
because of these lines in src/Makefile:

LIB_HARD_LOCALE = -lpthread
LIB_MBRTOWC = -lpthread
LIB_SETLOCALE_NULL = -lpthread

I can work around this unnecessary dynamic dependency for GNU Tar by 
removing $(LIB_HARD_LOCALE), $(LIB_MBRTOWC) and $(LIB_SETLOCALE_NULL) 
from the tar linking instructions. But this seems brittle, as these 
$(LIB_...) macros might expand to something other than a threading 
library in the future. Is there a better way?