https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112442
--- Comment #10 from Xi Ruoyao <xry111 at gcc dot gnu.org> --- (In reply to Adam Andersson from comment #9) > I was sure I had tried -fno-strict-aliasing without any difference, but I > guessed I messed up somehow. Sorry about that. > > Still, is it not strange that -Wall doesn't generate a warning about this > then? -Wall only enables -Wstrict-aliasing=3 which may have false negatives. -Wstrict-aliasing=1 or -Wstrict-aliasing=2 warns about this, but generally they can produce many false positives (as they are documented). Generally it's impossible to make a reliable way to detect aliasing violation at compile time. For runtime checking LLVM folks were developing a Type Sanitizer (https://llvm.org/devmtg/2017-10/slides/Finkel-The%20Type%20Sanitizer.pdf) but the development seems stalled now. Thus we document "try -fno-strict-aliasing" in the "new bug" page as a "not so bad" way to rule out aliasing issues (it's only "not so bad", not "very good" because it may still hide real bugs).
