On Mon, 20 Feb 2023 at 12:59, Xi Ruoyao <xry111@xxxxxxxxxxx> wrote: > > On Mon, 2023-02-20 at 11:30 +0000, Jonny Grant wrote: > > > Thank you for the suggestion, I gave that nonnull attribute a try, but > > it doesn't appear to warn for this example. > > > > https://godbolt.org/z/boqTj6oWE > > Ouch... The optimizer inlined make_std_string so both -Wnonnull and - > fanalyzer fails to catch the issue here. > > Adding noipa attribute for make_std_string will work, but will also > cause the generated code stupidly slow. Maybe: > > #ifdef WANT_DIAGNOSTIC > #define MAKE_STD_STRING_ATTR __attribute__ ((noipa, nonnull)) > #else > #define MAKE_STD_STRING_ATTR > #endif > > std::string make_std_string(const char * const str) MAKE_STD_STRING_ATTR; > > It still looks very stupid though. > > > Feels useful to get build warnings if compiler knows nullptr is going > > to be dereferenced, as clang does. > > The problem is in this case nullptr is not dereferenced, at all. So if > we want a warning here we'll have to invent some new __builtin or > __attribute__ to give the compiler a hint. AFAIK there is no such > facility now. I think __attribute__((access(read_only, 1))) should do it.
