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From: "romain.geissler at amadeus dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/98465] Bogus warning stringop-overread wuth -std=gnu++20 -O2 and std::string::insert
Date: Wed, 30 Dec 2020 13:22:59 +0000	[thread overview]
Message-ID: <bug-98465-4-U6UYdLHWql@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-98465-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98465

--- Comment #3 from Romain Geissler <romain.geissler at amadeus dot com> ---
I have found another example in my code base raising this error:

#include <string>

std::string f1()
{
    std::string aString = "string";
    aString = "bigger str";

    return aString;
}

With: -O2 -std=gnu++20 -Werror=stringop-overread -Wno-system-headers -g
raises:

/opt/compiler-explorer/gcc-trunk-20201230/include/c++/11.0.0/bits/char_traits.h:402:56:
error: 'void* __builtin_memcpy(void*, const void*, long unsigned int)' reading
10 bytes from a region of size 7 [-Werror=stringop-overread]
  402 |         return static_cast<char_type*>(__builtin_memcpy(__s1, __s2,
__n));
      |                                       
~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

Yet now what confuses me is that if I add copy of this function later using
bigger strings (so not exposing the bug), the new f2 function makes the warning
disappear form the f1 function:

#include <string>

std::string f1()
{
    std::string aString = "string";
    aString = "bigger str"; // <--- no more warning here when we have function
f2 !

    return aString;
}

std::string f2()
{
    std::string aString = "initial string with enough capacity";
    aString = "smaller str";

    return aString;
}

Why does having a function f2 affects warnings in function f1 ?

  parent reply	other threads:[~2020-12-30 13:22 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-28 18:36 [Bug middle-end/98465] New: " romain.geissler at amadeus dot com
2020-12-28 20:54 ` [Bug middle-end/98465] " msebor at gcc dot gnu.org
2020-12-30 12:49 ` romain.geissler at amadeus dot com
2020-12-30 13:22 ` romain.geissler at amadeus dot com [this message]
2020-12-30 21:25 ` msebor at gcc dot gnu.org
2021-01-06 22:38 ` msebor at gcc dot gnu.org
2021-01-06 22:59 ` msebor at gcc dot gnu.org
2021-01-06 23:14 ` msebor at gcc dot gnu.org
2021-01-07 20:26 ` msebor at gcc dot gnu.org
2021-01-13 18:19 ` msebor at gcc dot gnu.org
2021-01-13 18:41 ` law at redhat dot com
2021-01-13 18:52 ` jakub at gcc dot gnu.org
2021-01-13 19:02 ` msebor at gcc dot gnu.org
2021-01-13 19:14 ` jakub at gcc dot gnu.org
2021-01-13 19:30 ` msebor at gcc dot gnu.org
2021-01-14  2:21 ` msebor at gcc dot gnu.org
2021-01-19 19:00 ` msebor at gcc dot gnu.org
2021-01-20 23:20 ` [Bug middle-end/98465] [11 Regression] Bogus -Wstringop-overread with " msebor at gcc dot gnu.org
2021-02-04 14:03 ` jakub at gcc dot gnu.org
2021-02-04 14:39 ` redi at gcc dot gnu.org
2021-02-04 15:25 ` jakub at gcc dot gnu.org
2021-02-04 15:53 ` redi at gcc dot gnu.org
2021-02-04 15:54 ` redi at gcc dot gnu.org
2021-02-04 16:02 ` msebor at gcc dot gnu.org
2021-02-04 16:58 ` jakub at gcc dot gnu.org
2021-02-04 17:12 ` jakub at gcc dot gnu.org
2021-02-04 20:57 ` msebor at gcc dot gnu.org
2021-02-04 21:09 ` jakub at gcc dot gnu.org
2021-02-05 10:15 ` jakub at gcc dot gnu.org
2021-02-08 18:51 ` jakub at gcc dot gnu.org
2021-02-09 11:33 ` cvs-commit at gcc dot gnu.org
2021-02-09 11:35 ` [Bug middle-end/98465] " jakub at gcc dot gnu.org
2021-02-19 23:41 ` msebor at gcc dot gnu.org
2021-11-12 19:53 ` msebor at gcc dot gnu.org
2022-02-15  3:55 ` Randy at miningrigrentals dot com
2022-02-15  9:47 ` redi at gcc dot gnu.org
2022-02-15  9:55 ` Randy at miningrigrentals dot com
2022-02-15 10:02 ` redi at gcc dot gnu.org
2022-02-15 10:50 ` Randy at miningrigrentals dot com
2022-02-15 12:29 ` redi at gcc dot gnu.org
2022-02-15 12:40 ` Randy at miningrigrentals dot com
2022-02-15 12:52 ` redi at gcc dot gnu.org
2022-02-15 19:23 ` Randy at miningrigrentals dot com
2022-02-17 10:37 ` redi at gcc dot gnu.org

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