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From: "mimomorin at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/109891] New: Null pointer special handling in ostream's operator << for C-strings Date: Wed, 17 May 2023 14:20:25 +0000 [thread overview] Message-ID: <bug-109891-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109891 Bug ID: 109891 Summary: Null pointer special handling in ostream's operator << for C-strings Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: mimomorin at gmail dot com Target Milestone: --- This code #include <iostream> int main() { std::cout << (char*)nullptr; } does not cause any bad things (like SEGV), because libstdc++'s operator<<(ostream, char const*) has special handling of null pointers: template<typename _CharT, typename _Traits> inline basic_ostream<_CharT, _Traits>& operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s) { if (!__s) __out.setstate(ios_base::badbit); else __ostream_insert(...); return __out; } Passing a null pointer to this operator is a precondition violation, so the current implementation perfectly conforms to the C++ standard. But, why don't we remove this special handling? By doing so, we get - better interoperability with toolings (i.e. sanitizers can find the bug easily) - unnoticeable performace improvement and we lose - deterministic behaviors (of poor codes) on a particular stdlib I believe the first point makes more sense than the last point. It seems that old special handling `if (s == NULL) s = "(null)";` (https://github.com/gcc-mirror/gcc/blob/6599da0/libio/iostream.cc#L638) was removed in GCC 3.0, but reintroduced (in the current form) in GCC 3.2 in response to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=6518 .
next reply other threads:[~2023-05-17 14:20 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-17 14:20 mimomorin at gmail dot com [this message] 2023-05-17 14:28 ` [Bug libstdc++/109891] " redi at gcc dot gnu.org 2023-05-17 14:32 ` redi at gcc dot gnu.org 2023-05-17 15:10 ` mimomorin at gmail dot com 2023-05-17 15:13 ` pinskia at gcc dot gnu.org 2023-05-17 16:52 ` redi at gcc dot gnu.org 2023-05-18 15:08 ` mimomorin at gmail dot com 2023-05-18 15:36 ` redi at gcc dot gnu.org 2023-05-18 16:01 ` xry111 at gcc dot gnu.org 2023-05-20 12:58 ` mimomorin at gmail dot com 2023-07-09 21:33 ` pinskia at gcc dot gnu.org
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