https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70792
Bug ID: 70792
Summary: Incorrect sequence point warning with uniform
initializer syntax
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: lefticus at gmail dot com
Target Milestone: ---
The following code:
#include
struct Do_Call
{
template
Do_Call(const Func &f, T && ... t)
{
f(std::forward(t)...);
}
};
int main()
{
const auto sum = [](int w, int x, int y, int z) {
return w + x + y + z;
};
int i = 0;
Do_Call{sum, ++i, ++i, ++i, ++i};
}
Generates the -Wsequence-point warning for the variable 'i'. However, the
standard states:
"Within the initializer-list of a braced-init-list, the initializer-clauses,
including any that result from pack expansions (14.5.3), are evaluated in the
order in which they appear. That is, every value computation and side effect
associated with a given initializer-clause is sequenced before every value
computation and side effect associated with any initializer-clause that follows
it in the comma-separated list of the initializer-list. [Note: This evaluation
ordering holds regardless of the semantics of the initialization; for example,
it applies when the elements of the initializer-list are interpreted as
arguments of a constructor call, even though ordinarily there are no sequencing
constraints on the arguments of a call. —end note ]"
The "Note: This evaluation ordering holds regardless of the semantics of the
initialization; for example, it applies when the elements of the
initializer-list are interpreted as arguments of a constructor call, even
though ordinarily there are no sequencing constraints on the arguments of a
call. —end note" is the most applicable to this bug report.
This occurs in all versions tested between 4.7.3->6
