buffer. If snprintf truncated the output, the length returned will be
greater and we'll write trash. Just call strlen instead. (And since
what we're doing is writing progress messages to the user, checking
carefully for truncation isn't really worthwhile either.)
Spotted when attending to PR 50998 from David Binderman; the issue
there (computation of an unused value) popped up because one of the
prints was already calling strlen.
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