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]; }