Re: [configure bus while building] flex beta version 2.5.15

[Bruce Lilly]

Akim Demaille wrote:

> | 2. configure uses the following in a failed attempt to determine the
> |     default compiler output file name:
> | 
> | # Be careful to initialize this variable, since it used to be cached.
> | # Otherwise an old cache value of `no' led to `EXEEXT = no' in a Makefile.
> | ac_cv_exeext=
> | for ac_file in `ls a_out.exe a.exe conftest.exe 2>/dev/null;
> |                  ls a.out conftest 2>/dev/null;
> |                  ls a.* conftest.* 2>/dev/null`; do
> |    case $ac_file in
> |      *.$ac_ext | *.o | *.obj | *.xcoff | *.tds | *.d | *.pdb | *.xSYM ) ;;
> |      a.out ) # We found the default executable, but exeext='' is most
> |              # certainly right.
> |              break;;
> |      *.* ) ac_cv_exeext=`expr "$ac_file" : '[^.]*\(\..*\)'`
> |            # FIXME: I believe we export ac_cv_exeext for Libtool --akim.
> |            export ac_cv_exeext
> |            break;;
> |      * ) break;;
> |    esac
> | done
> | 
> | That's:
> | a: non-portable (in some cases, ls reports something like
> |     a_out.exe not found
> |     on stdout, which configure misinterprets as an indication that
> |     a_out.exe exists...)
>
> Great!  Please, show where you observed this, so that we can document
> this problem (an `ls' that reports errors on stdout).

# telnet dim
[...]
 UNIX System V (TWG-TCP/IP) (dim.blilly.com)
[...]
$ mkdir foo
$ cd foo
$ /bin/ls a.exe 2>/dev/null
a.exe not found
$ what /bin/ls
/bin/ls:
         fndcmd:fndcmd.sl 1.68
$ uname -a
UNIX dim SYSTEM5 3.51m mc68k
$ cd
$ rm -rf foo
$ exit

> | and
> | b: inefficient
> | 
> | It should be something like:
> | 
> | # Be careful to initialize this variable, since it used to be cached.
> | # Otherwise an old cache value of `no' led to `EXEEXT = no' in a Makefile.
> | ac_cv_exeext=
> | for ac_file in a_out.exe a.exe conftest.exe a.out conftest a.* conftest.* ; do
> |    if test -x $ac_file ; then
> |      case $ac_file in
> |        *.$ac_ext | *.o | *.obj | *.xcoff | *.tds | *.d | *.pdb | *.xSYM ) ;;
> |        a.out ) # We found the default executable, but exeext='' is most
> |                # certainly right.
> |                break;;
> |        *.* ) ac_cv_exeext=`expr "$ac_file" : '[^.]*\(\..*\)'`
> |              # FIXME: I believe we export ac_cv_exeext for Libtool --akim.
> |              export ac_cv_exeext
> |              break;;
> |        * ) break;;
> |      esac
> |      break
> |    fi
> | done
> | 
> | There are similar tests throughout the configure script.
>
> That's better, indeed.  Just -f instead of -x.

Using -x ensures that only executables are found; a further
improvement (w.r.t. maintainability) would then be to remove
all the .o .obj .xcoff .tds .d .pdb .xSYM cruft [of course,
if configure didn't insist on using -g when compiling throw-
away programs, much of that would have been unnecessary in
the first place...].