lambda
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switch statement case label has only `int` template argument
Before gcc9, if a template argument is an integral value, no compiler error/warning generated when the specified value is bigger than the integral value MAX.
This leads the following runtime issue:
#include <iostream>
#include <boost/lambda/lambda.hpp>
#include <boost/lambda/switch.hpp>
int main() {
using namespace boost;
using namespace boost::lambda;
switch_statement(
_1,
case_statement<2147483648>(std::cout << constant("big")),
default_statement(std::cout << constant("other"))
)(2147483648); // prints 'other'
// static_cast<int>(2147483648) is OK
}
This issue prone working can be eliminated in any following way:
- replace case_statement template argument from
int
touintmax_t
orintmax_t
or any bigger than int. This solves that not onlyint
parameters can be accepted in later gcc's and clang too. - switch_statement lambda accepts/casts argument
int
. This solves type safety. - some other template magic, where at case statement can be set the acceptable integral type, and switch statement recognizes, and uses
common_type
to casts lambda parameter to that.