https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83990
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Martin Jambor from comment #7) > (In reply to Jakub Jelinek from comment #4) > > > > ... > > > > The statement on which on the original testcase it warns indeed has no > > location, that was created during IPA optimizations: > > ipa_modify_call_arguments does: > > loc = DECL_P (base) ? DECL_SOURCE_LOCATION (base) > > : EXPR_LOCATION (base); > > This itself is weird in this case, base is a SSA_NAME this_4(D), so has no > > location and loc is UNKNOWN_LOCATION. > > Interesting, I see base being an ADDR_EXPR on trunk. But anyway... Are you looking at the #c0 testcase or the reduced one? The reduced one only shows the -Wnull-dereference warning, with correct location. Only the original one has the UNKNOWN_LOCATION on the statement on which the warning is emitted. > That might indeed make more sense, I will look into it. > > But please note that I get exactly the same warning when I add > -fno-ipa-sra on the command line (and I have verified in gdb that > ipa_modify_call_arguments is not invoked at all with the option just > to double check) so ipa_modify_call_arguments cannot be the whole > story. -fno-ipa-sra makes the warning go away altogether for me on the trunk on the original testcase: ./cc1plus -quiet -std=c++17 -O3 -Wnull-dereference pr83990.ii; echo ===; \ ./cc1plus -quiet -std=c++17 -O3 -Wnull-dereference pr83990.ii -fno-ipa-sra; \ echo === In function ‘void std::vector<_Tp, _Alloc>::reserve(std::vector<_Tp, _Alloc>::size_type) [with _Tp = std::__cxx11::basic_string<char>; _Alloc = std::allocator<std::__cxx11::basic_string<char> >]’: cc1plus: warning: potential null pointer dereference [-Wnull-dereference] === ===
