https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115160
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
CC| |jakub at gcc dot gnu.org
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This is just bogus testcase, anything can happen.
If you use
unsigned char data[] = { 1, 0, 0, 0 }, *b = data;
instead of the
std::vector<uint8_t> data;
data.emplace_back(1);
data.emplace_back(0);
data.emplace_back(0);
data.emplace_back(0);
auto b = data.begin();
lines, g++ -Wall diagnoses it:
pr115160.C: In function ‘int main()’:
pr115160.C:12:50: warning: operation on ‘b’ may be undefined [-Wsequence-point]
12 | std::cout << (int)( (*b++) | (*b++ << 8) | (*b++ << 16 ) | ( *b <<
24 ) )<< std::endl;
| ~^~
pr115160.C:12:50: warning: operation on ‘b’ may be undefined [-Wsequence-point]
pr115160.C:12:50: warning: operation on ‘b’ may be undefined [-Wsequence-point]
pr115160.C:12:50: warning: operation on ‘b’ may be undefined [-Wsequence-point]
While https://wg21.link/p0145r3 in C++17 made evaluation order in some cases
well defined, it certainly didn't do that for non-overloaded operator| or
similar operators.
