Re: [PATCH] top-level configure: setup target_configdirs based on repository

[Richard Biener <richard.guenther@gmail.com>]

On Wed, Sep 22, 2021 at 5:47 PM Andrew Burgess
<andrew.burgess@embecosm.com> wrote:
>
> The top-level configure script is shared between the gcc repository
> and the binutils-gdb repository.
>
> The target_configdirs variable in the configure.ac script, defines
> sub-directories that contain components that should be built for the
> target using the target tools.
>
> Some components, e.g. zlib, are built as both host and target
> libraries.
>
> This causes problems for binutils-gdb.  If we run 'make all' in the
> binutils-gdb repository we end up trying to build a target version of
> the zlib library, which requires the target compiler be available.
> Often the target compiler isn't immediately available, and so the
> build fails.
>
> The problem with zlib impacted a previous attempt to synchronise the
> top-level configure scripts from gcc to binutils-gdb, see this thread:
>
>   https://sourceware.org/pipermail/binutils/2019-May/107094.html
>
> And I'm in the process of importing libbacktrace in to binutils-gdb,
> which is also a host and target library, and triggers the same issues.
>
> I believe that for binutils-gdb, at least at the moment, there are no
> target libraries that we need to build.
>
> My proposal then is to make the value of target_libraries change based
> on which repository we are building in.  Specifically, if the source
> tree has a gcc/ directory then we should set the target_libraries
> variable, otherwise this variable is left entry.
>
> I think that if someone tries to create a single unified tree (gcc +
> binutils-gdb in a single source tree) and then build, this change will
> not have a negative impact, the tree still has gcc/ so we'd expect the
> target compiler to be built, which means building the target_libraries
> should work just fine.
>
> However, if the source tree lacks gcc/ then we assume the target
> compiler isn't built/available, and so target_libraries shouldn't be
> built.
>
> There is already precedent within configure.ac for check on the
> existence of gcc/ in the source tree, see the handling of
> -enable-werror around line 3658.
>
> I've tested a build of gcc on x86-64, and the same set of target
> libraries still seem to get built.  On binutils-gdb this change
> resolves the issues with 'make all'.
>
> Any thoughts?

Hmm, why not use make all-binutils instead?  Otherwise this does
look like a reasonable thing to do.

Richard.

> ChangeLog:
>
>         * configure: Regenerate.
>         * configure.ac (target_configdirs): Only set this when building
>         within the gcc repository.
> ---
>  ChangeLog    |  6 ++++++
>  configure    | 12 ++++++++++--
>  configure.ac | 12 ++++++++++--
>  3 files changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/configure b/configure
> index 85ab9915402..3ef5c2b553f 100755
> --- a/configure
> +++ b/configure
> @@ -2849,9 +2849,17 @@ target_tools="target-rda"
>  ## We assign ${configdirs} this way to remove all embedded newlines.  This
>  ## is important because configure will choke if they ever get through.
>  ## ${configdirs} is directories we build using the host tools.
> -## ${target_configdirs} is directories we build using the target tools.
> +##
> +## ${target_configdirs} is directories we build using the target
> +## tools, these are only needed when working in the gcc tree.  This
> +## file is also reused in the binutils-gdb tree, where building any
> +## target stuff doesn't make sense.
>  configdirs=`echo ${host_libs} ${host_tools}`
> -target_configdirs=`echo ${target_libraries} ${target_tools}`
> +if test -d ${srcdir}/gcc; then
> +  target_configdirs=`echo ${target_libraries} ${target_tools}`
> +else
> +  target_configdirs=""
> +fi
>  build_configdirs=`echo ${build_libs} ${build_tools}`
>
>
> diff --git a/configure.ac b/configure.ac
> index 1df038b04f3..d1217e3f886 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -180,9 +180,17 @@ target_tools="target-rda"
>  ## We assign ${configdirs} this way to remove all embedded newlines.  This
>  ## is important because configure will choke if they ever get through.
>  ## ${configdirs} is directories we build using the host tools.
> -## ${target_configdirs} is directories we build using the target tools.
> +##
> +## ${target_configdirs} is directories we build using the target
> +## tools, these are only needed when working in the gcc tree.  This
> +## file is also reused in the binutils-gdb tree, where building any
> +## target stuff doesn't make sense.
>  configdirs=`echo ${host_libs} ${host_tools}`
> -target_configdirs=`echo ${target_libraries} ${target_tools}`
> +if test -d ${srcdir}/gcc; then
> +  target_configdirs=`echo ${target_libraries} ${target_tools}`
> +else
> +  target_configdirs=""
> +fi
>  build_configdirs=`echo ${build_libs} ${build_tools}`
>
>  m4_divert_text([PARSE_ARGS],
> --
> 2.25.4
>