Shell functions pointlessly specialized on _AC_LANG_ABBREV

[Zack Weinberg]

While poking at something else, I happened to notice that we seem to be
defining redundant copies of many shell functions, one for each language
under test. Concretely, if you do this:

AC_INIT([test], [0.0.0])
AC_CONFIG_HEADERS([config.h])

AC_PROG_CC
AC_PROG_CXX

AC_LANG([C])
AC_CHECK_HEADERS([stddef.h])
AC_LANG([C++])
AC_CHECK_HEADERS([cstddef])

AC_OUTPUT

the generated configure script will contain functions named
'ac_fn_c_check_header_compile' and 'ac_fn_cxx_check_header_compile' (and
also 'ac_fn_c_try_compile' and 'ac_fn_cxx_try_compile') whose bodies are
character-for-character identical, and both of which depend on the
variables set and reset by AC_LANG to control the compiler actually in
use. It looks like it has been this way since the shell functions were
introduced back in 2008.

What was the intention, here? Right now it seems to me that it would
make most sense to remove _AC_LANG_ABBREV from the function names (so
there would be just one of each, and it would still depend on the
current AC_LANG setting).

zw

[Eric Blake]

Post by Zack Weinberg
While poking at something else, I happened to notice that we seem to be
defining redundant copies of many shell functions, one for each language
AC_INIT([test], [0.0.0])
AC_CONFIG_HEADERS([config.h])
AC_PROG_CC
AC_PROG_CXX
AC_LANG([C])
AC_CHECK_HEADERS([stddef.h])
AC_LANG([C++])
AC_CHECK_HEADERS([cstddef])
AC_OUTPUT
the generated configure script will contain functions named
'ac_fn_c_check_header_compile' and 'ac_fn_cxx_check_header_compile' (and
also 'ac_fn_c_try_compile' and 'ac_fn_cxx_try_compile') whose bodies are
character-for-character identical, and both of which depend on the
variables set and reset by AC_LANG to control the compiler actually in
use. It looks like it has been this way since the shell functions were
introduced back in 2008.
What was the intention, here? Right now it seems to me that it would
make most sense to remove _AC_LANG_ABBREV from the function names (so
there would be just one of each, and it would still depend on the
current AC_LANG setting).

I think the original goal was to ensure if there ARE any language
dependencies on the function bodies, that we have the right setup to
differentiate between them. But you are welcome to try and patch things
to use fewer functions if they really did end up being identical in a
project that targets both languages.