This tests for a bug that was introduced in commit edc1686a ("vfprintf: Reuse work_buffer in group_number") and fixed as a side effect of commit 6caddd34 ("Remove most vfprintf width/precision-dependent allocations (bug 14231, bug 26211).").
mentioned in commit 8b915921
mentioned in commit 6da40102
mentioned in commit d0aac8b4
mentioned in commit c8f2a3e8
