[Bug c/80354] Poor support to silence -Wformat-truncation=1

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80354

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning does just what it's designed to do: point out the potential
unhandled truncation.  If the argument values are such that the truncation
cannot occur then using snprintf is unnecessary and sprintf can be used
instead.  Otherwise, if there is a combination of argument values that can
result in truncation a warning is issued.  Note that the length of output
produced by each directive can be constrained by specifying a precision for %s
(e.g., "%.24s" if arena->m_name in the LibreOffice code cannot be longer than
24 characters), or by asserting that an integer argument is in some limited
range of its type (or by using a narrower type to store it).

Like all warnings that depend on data flow analysis it is subject to false
positives but there is no evidence to suggest that on balance it's unhelpful or
difficult to use.  Quite the contrary.