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* [Bug c++/101119] New: Missing the check about modify global variable for __attribute__((const)) function
@ 2021-06-18 10:56 zhongyunde at huawei dot com
2021-06-18 12:37 ` [Bug c++/101119] " rguenth at gcc dot gnu.org
2021-06-18 17:05 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: zhongyunde at huawei dot com @ 2021-06-18 10:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101119
Bug ID: 101119
Summary: Missing the check about modify global variable for
__attribute__((const)) function
Product: gcc
Version: 10.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: zhongyunde at huawei dot com
Target Milestone: ---
As __attribute__((const)) function should have no side effect, so it won't
modify any global variable. but with the newest gcc, it doesn't do such check.
test base on the ARM64 gcc 11.1 on https://gcc.godbolt.org/ with option -O3 -S
-fno-inline -g0 -Wall -Werror.
=====================================================
#include <stdio.h>
int gValue = 1;
class NPair /*: protected Pointers */ {
public:
int bins[10];
//int exclusion(int n) __attribute__((const));
__attribute__((const)) int exclusion (int n) const {
printf ("before %d\n", bins[0]);
NPair* pt = const_cast<NPair*>(this);
pt->bins[0] = 1;
printf ("after %d\n", bins[0]);
return gValue++; // expect a error
}
NPair (void) {
bins[0] = 3;
}
};
// extern int * __restrict bins;
class NPair nPair;
int main (void)
{
int tmp = nPair.bins[0];
(void)nPair.exclusion(1);
return tmp == nPair.bins[0];
}
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2021-06-18 10:56 [Bug c++/101119] New: Missing the check about modify global variable for __attribute__((const)) function zhongyunde at huawei dot com
2021-06-18 12:37 ` [Bug c++/101119] " rguenth at gcc dot gnu.org
2021-06-18 17:05 ` pinskia at gcc dot gnu.org
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