[Bug build/23681] New: Program environment variables (AR, LD, AS, ...) are ignored

[John.Ericson at Obsidian dot Systems]

https://sourceware.org/bugzilla/show_bug.cgi?id=23681

            Bug ID: 23681
           Summary: Program environment variables (AR, LD, AS, ...) are
                    ignored
           Product: glibc
           Version: 2.27
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: build
          Assignee: unassigned at sourceware dot org
          Reporter: John.Ericson at Obsidian dot Systems
                CC: carlos at redhat dot com
  Target Milestone: ---

In [aclocal.m4], we have the following:

  AS=`$CC -print-prog-name=as`
  LD=`$CC -print-prog-name=ld`
  AR=`$CC -print-prog-name=ar`
  ...

This is not idiomatic autoconf usage and causes user-specifications of those
environment variables to be ignored. There is a `--with-binutils` which at
least adds some `-B` flags to $CC so that more directories are searched, but
that doesn't work well in all use-cases. (The programs can be scattered around
various directories, as they are on my distro NixOS.) Why not use the standard
autoconf macros? Or at least take the path of the variables' old value if they
is defined and non-empty?

I did some digging in the history to try to answer those questions, and did not
come up with good answers.

  1. In [ff3d7ed36ae26261cc1c76e5f03ee053d65f9229] in 1995, using the idiomatic
AC_CHECK_TOOL.

  2. In [650425ceb40e840b2123b6c8cc65389589f41218] in 1997 The first instance
of this was added for AS and LD.

  3. In [650425ceb40e840b2123b6c8cc65389589f41218] in 1998 some of the
AC_CHECK_TOOL usages were changed to match the second *without explanation*.

  4. ...more programs added matching the status quo, probably just Cargo cults.

Without any explanation it's hard to tell what's going on, but I can't see
there being a problem with things like:

  AC_CHECK_TOOL(AR, ar, `$CC -print-prog-name=as`)

That would restore the idiom while preserving behavior when nothing is
specified.


[aclocal.m4]:
https://sourceware.org/git/?p=glibc.git;a=blob;f=aclocal.m4;hb=HEAD#l116

[ff3d7ed36ae26261cc1c76e5f03ee053d65f9229]:
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=ff3d7ed36ae26261cc1c76e5f03ee053d65f9229

[650425ceb40e840b2123b6c8cc65389589f41218]:
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=650425ceb40e840b2123b6c8cc65389589f41218

[650425ceb40e840b2123b6c8cc65389589f41218]:
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=6[50425ceb40e840b2123b6c8cc65389589f41218

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