* Bug in GCC 7.1?
@ 2017-05-05 9:21 Helmut Zeisel
2017-05-05 9:51 ` Marc Glisse
0 siblings, 1 reply; 3+ messages in thread
From: Helmut Zeisel @ 2017-05-05 9:21 UTC (permalink / raw)
To: gcc
The following program gives a warning under GCC 7.1 (built on cygwin, 64 bit)
#include <vector>
int main()
{
std::vector<int> c {1,2,3,0};
while(c.size() > 0 && c.back() == 0)
{
auto sz = c.size() -1;
c.resize(sz);
}
return 0;
}
$ c++7.1 -O3 tt.cxx
In Funktion »int main()«:
cc1plus: Warnung: »void* __builtin_memset(void*, int, long unsigned int)«: angegebene Größe 18446744073709551612 überschreitet maximale Objektgröße 9223372036854775807 [-Wstringop-overflow=]
Compiling with GCC 6.1 (c++6.1 -O3 tt.cxx) works fine.
Is this a problem of my program or a problem of GCC 7.1?
Helmut
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: Bug in GCC 7.1?
2017-05-05 9:21 Bug in GCC 7.1? Helmut Zeisel
@ 2017-05-05 9:51 ` Marc Glisse
2017-05-05 10:14 ` Helmut Zeisel
0 siblings, 1 reply; 3+ messages in thread
From: Marc Glisse @ 2017-05-05 9:51 UTC (permalink / raw)
To: Helmut Zeisel; +Cc: gcc
(I think you are looking for gcc-help@gcc.gnu.org, or gcc's bugzilla,
rather than this mailing list)
On Fri, 5 May 2017, Helmut Zeisel wrote:
> The following program gives a warning under GCC 7.1 (built on cygwin, 64 bit)
>
> #include <vector>
> int main()
> {
> std::vector<int> c {1,2,3,0};
> while(c.size() > 0 && c.back() == 0)
> {
> auto sz = c.size() -1;
> c.resize(sz);
> }
> return 0;
> }
>
> $ c++7.1 -O3 tt.cxx
Please use
$ LC_ALL=C c++7.1 -O3 tt.cxx
when you want to post the result, unless you are sending to a German
forum.
> In Funktion »int main()«:
> cc1plus: Warnung: »void* __builtin_memset(void*, int, long unsigned int)«: angegebene Größe 18446744073709551612 überschreitet maximale Objektgröße 9223372036854775807 [-Wstringop-overflow=]
>
> Compiling with GCC 6.1 (c++6.1 -O3 tt.cxx) works fine.
>
> Is this a problem of my program or a problem of GCC 7.1?
Sounds like a problem with gcc, maybe optimization creates a path that
corresponds to size==0 and fails to notice that it cannot be taken.
--
Marc Glisse
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2017-05-05 9:21 Bug in GCC 7.1? Helmut Zeisel
2017-05-05 9:51 ` Marc Glisse
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