Re: bison 3.7.1 failing to build due to autoconf cache

[Bruno Haible]

Hi Paul,

Paul Smith wrote:
> > If I compare the configure output from a run with using the cache
> > (fails) with one that doesn't use the cache (succeeds) the only
> > difference of interest is:
> 
>   -checking for sigprocmask... (cached) 1
>   +checking for sigprocmask... yes
>      ...
>   -checking for sigprocmask... (cached) 1
>   +checking for sigprocmask... yes

The situation with the Autoconf cache is not pretty: The documentation
merely states how the caching works, but
  - neither when and how the 'configure' user is meant to use it,
  - nor how an Autoconf macro should be written for good interoperation
    with the cache.

More than 15 years ago, I heard "the autoconf cache is broken". As I
realized that the cache's contents depend on
  - the package you are compiling,
  - the version of a .m4 file with an autoconf macro,
  - the values of $CC and $CFLAGS (even '-m32' vs. '-m64'),
I stopped using it (except for collecting known values for cross-
compilation).

If you think that certain uses of the Autoconf cache can be made to
work reliably, please go ahead and document in the Autoconf manual
  - what these uses are,
  - what an Autoconf macro author should do for it to work.

Bruno