halt: switch __progname tests to use strncmp

[heliocat]

The pending change to allow for alternate init power controls requires
that the halt binary provided here be somewhat less strict in its
argv[0] matching in order to allow for halt, reboot, and poweroff to
still function in situations where the binary has been renamed.

This switches from strcmp(__progname, "string") to strncmp(__progname,
"string", len), where len is the name of the power command sans any
suffix.

Signed-off-by: Colin Booth colin@heliocat.net

[heliocat]

@Duncaen @leahneukirchen

[pullmoll]

Just a personal preference because I refrain from using numeric constants for string lengths. This has been proven to be error prone in copy+pasta cases.

static const char s_halt[] = "halt";
static const char s_reboot[] = "reboot";
static const char s_poweroff[] = "poweroff";

…

if (strncmp(__progname, s_halt, sizeof(s_halt)-1) == 0)
    action = HALT;
if (strncmp(__progname, s_reboot, sizeof(s_reboot)-1) == 0)
    action = REBOOT;
if (strncmp(__progname, s_poweroff, sizeof(s_poweroff)-1) == 0)
    action = POWEROFF;

The else if is IMO redundant, i.e. last hit wins...

Just my .02€

[heliocat]

Just a personal preference because I refrain from using numeric constants for string lengths. This has been proven to be error prone in copy+pasta cases.

static const char s_halt[] = "halt";
static const char s_reboot[] = "reboot";
static const char s_poweroff[] = "poweroff";

…

if (strncmp(__progname, s_halt, sizeof(s_halt)-1) == 0)
    action = HALT;
if (strncmp(__progname, s_reboot, sizeof(s_reboot)-1) == 0)
    action = REBOOT;
if (strncmp(__progname, s_poweroff, sizeof(s_poweroff)-1) == 0)
    action = POWEROFF;

The else if is IMO redundant, i.e. last hit wins...

Just my .02€

Thanks. I'll keep that in mind if we ever give this a more heavy refactor but I wanted to keep the diff as minimal as possible.