https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80354
--- Comment #2 from Stephan Bergmann <sbergman at redhat dot com> --- But that makes this warning extremely hard to use. Is it really useful for -Wall in that case? I came across this with a real-world use-case in the LibreOffice code base, where some code deliberately uses snprintf to produce a fixed-size prefix, see <https://gerrit.libreoffice.org/#/c/36211/> "WaE: ‘%lu’ directive output may be truncated". (And older builds of GCC towards GCC 7 did not emit that unhelpful warning with -Wall => -Wformat-truncation=1, but would only have emitted it with an explicit -Wformat-truncation=2.) Addressing false positives for this warning thus becomes an unpleasant whack-a-mole (given different builds of the code are done with different optimization switches), unpleasant enough so that we'll likely have to use -Wall -Wformat-truncation=0 for LibreOffice. Which is unfortunate, given that casting-to-void would be a well-understood and well-accepted way to silence false positives (but one hard to implement in GCC, if I understand you correctly).
