boost::program_options::parse_command_line crashes with argc of ISO Cpp valid value of 0 #127
Description
boost::program_options::parse_command_line(argc, argv, parameters) invokes undefined behavior and crashes with a value of argc of 0 (and argv nullptr).
These values for argc and argv are perfectly valid according to
6.9.3.1 main function[basic.start.main]
The value of argc shall be non-negative. The value of argv[argc] shall be 0.
(Of course this assumes 0 is non-negative, but the cpp standard seems to assume this too as it states „If argc is nonzero these arguments shall…“).
To be fair, almost none implementation might uses 0, when writing an integration test, as I did, that surrogates argc and argv, as any regular parameter for this boost function, I would expect no UB, when not violating any API contract.
Looking at the code this is no suprise as
basic_command_line_parser(int argc, const charT* const argv[])
: detail::cmdline(
to_internal(std::vector<std::basic_string<charT> >(argv+1, argv+argc))),
uses the std::vector(begin,end) constructor, however with argc of 0, end will be < than begin, hence undefined behaviour and luckily an exception.
Older boost code did righteously check for argc == 0
basic_command_line_parser(int argc, const charT* const argv[])
: detail::cmdline(
to_internal(std::vector<std::basic_string<charT> >(
// When argc == 0, we must produce a valid empty range,
// even with a nullptr argv. We can ignore the
// obviously illegal argc < 0.
argc ? argv+1 : argv, argv+argc))),
#include <boost/program_options.hpp>
int main() {
boost::program_options::options_description parameters("Parameters");
int argc = 0; //Allowed value see https://eel.is/c++draft/basic.start.main#2.2
char* argv[] {nullptr};
boost::program_options::parse_command_line(argc, argv, parameters);
}
crashes, luckily with an exception from std::vector