configuring base requires working tclsh

[ryandesign (Ryan Carsten Schmidt)]

It was a surprise to me to discover that tcllib's configure script, which our configure script runs, requires a working tclsh, and that if ${prefix}/libexec/macports/bin/tclsh8.5 exists, it will choose that one. This is a problem when ${prefix}/libexec/macports/bin/tclsh8.5 exists but is broken, which was the case on my system and was one of the reasons why I was trying to rebuild from source.

The symptom was:

Installing Tcllib 1.18
You have chosen the following configuration ...

Packages:      /Users/rschmidt/macports-base/vendor/vendor-destroot/opt/local/libexec/macports/lib/.
Applications:  Not installed.
Examples:      Not installed.
Documentation: Not installed.
[snip]
chmod: /Users/rschmidt/macports-base/vendor/vendor-destroot/opt/local/libexec/macports/lib/tcllib*: No such file or directory

The packages path is wrong! It should not end with lib/.; it should end with lib/tcllib1.18.

tcllib's configure script replaces placeholder strings @PACKAGE@ and @VERSION@ with values computed by a script called sak.tcl. The version consists of the major version, then a literal dot, then the minor version. Since in my case tclsh did not work, the package, major and minor version strings were empty, leaving only the literal dot.

My workaround was to move the directory ${prefix} to ${prefix}old, then run configure and make, then move ${prefix}old back to ${prefix}, then sudo make install.

Apple has announced that scripting languages like tclsh won't necessarily be included in future versions of macOS. We should modify our build process so that we first build tclsh, and only then do we configure tcllib and point it at the tclsh that we built.

[jmroot (Joshua Root)]

Yes, this came up when our vendored Tcl was first added, and is why https://www.macports.org/install.php#other still lists Tcl as a build requirement.

[jmroot (Joshua Root)]

In 2eeba4da73a93102cac669ea55c1946c401730ec/macports-base (master):

Allow building without an external tclsh

Fixes: #61253