spin2cpp Byte and ~ Error

SRLM

When converting the read_pulse_widths from the Eddie project I get the following error:

read_pulse_widths.cpp:40:11: warning: promoted ~unsigned is always non-zero [-Wsign-compare]

It looks like the problem code is

uint8_t	Cog;

int32_t read_pulse_widths::Stop(void)
{
  if (~Cog) {
    cogstop(Cog);
  }
  return 0;
}

And the spin source:

VAR

  byte                cog

PUB Stop                        'Stop the currently running cog, if any

  if !cog
    cogstop(cog)

Dave Hein

It's actually a warning that says that since Cog is a uint8_t "if (~Cog)" will always succeed. This is because the Cog will be promoted to a uint32_t, and since the upper bits are zero, the complement will always be non-zero.

It appears that there's an error in the original Spin code. The normal practice is to set Cog to the return value of cognew plus 1, and to test Cog for a non-zero value when doing a cogstop. The logic in the current Spin code is incorrect.

SRLM

Dave Hein wrote: »

It's actually a warning that says that since Cog is a uint8_t "if (~Cog)" will always succeed. This is because the Cog will be promoted to a uint32_t, and since the upper bits are zero, the complement will always be non-zero.

It appears that there's an error in the original Spin code. The normal practice is to set Cog to the return value of cognew plus 1, and to test Cog for a non-zero value when doing a cogstop. The logic in the current Spin code is incorrect.

Oops. You're right: the spin code does have an error. I'm making a list of the bugs in Eddie so I'll be sure to add that one. Thanks for catching it.