kerberos5: Avoid embedding full paths in generated files

[markj]

Summary

When reproducible builds are enabled, we want to use /usr/src and
/usr/obj as the canonical src and obj paths.

Various files generated by the Heimdal Kerberos builds embed the
original source path in generated files. It doesn't look like the
utilities which generate those files can be taught to perform
substitution, so the easiest thing to do is fix them up after the fact.

[emaste]

No objection from me

[cy]

[brooks]

I fear the underlying code code isn't safe. The problem is that each of the value of GEN_* is a target on its own. As a demonstrator I created a trivial makefile:

GEN=a b c d
${GEN}:
        touch ${GEN}

I you ask it to make multiple targets in parallel with something like make -j40 a b c d the generator runs more than once:

--- a ---
--- b ---
--- c ---
--- d ---
--- a ---
touch a b c d
--- b ---
touch a b c d
--- c ---
touch a b c d
--- d ---
touch a b c d

It probably works out ok in practice because it just recreates the files with the same contents, but I'm afraid adding the sed will introduce more races. I'm not sure what the correct solution is. Make doesn't really deal well with multiple outputs.

[markj]

In D50952#1182272, @brooks wrote:

I fear the underlying code code isn't safe. The problem is that each of the value of GEN_* is a target on its own. As a demonstrator I created a trivial makefile:

GEN=a b c d
${GEN}:
        touch ${GEN}

I you ask it to make multiple targets in parallel with something like make -j40 a b c d the generator runs more than once:

--- a ---
--- b ---
--- c ---
--- d ---
--- a ---
touch a b c d
--- b ---
touch a b c d
--- c ---
touch a b c d
--- d ---
touch a b c d

It probably works out ok in practice because it just recreates the files with the same contents, but I'm afraid adding the sed will introduce more races. I'm not sure what the correct solution is. Make doesn't really deal well with multiple outputs.

Ah, I hadn't realized this. Absent a clear solution and given that Heimdal kerberos is no longer the default (and krb5 doesn't have any reproducibility problems that I've found), I'm inclined to just drop this.

[kevans]

Note that all of these have .ORDER declarations a few lines up that effectively serializes all of the generated targets.