favor comparison against 0 for error checking

When possible, comparisons against zero require one less load
and uses one less register, so this results in smaller code:

  $ ~/linux/scripts/bloat-o-meter before.so after.so
  add/remove: 0/0 grow/shrink: 0/5 up/down: 0/-57 (-57)
  function                                     old     new   delta
  rm_watch                                      84      83      -1
  rb_sp_set_nonblock                            80      79      -1
  add_watch                                    127     126      -1
  epwait                                       692     687      -5
  s_new                                        970     921     -49

This style is favored by major C projects, including glibc.

Note: since file and file descriptor flags may eventually use
more bits of an integer, we continue comparing F_GETFD/F_GETFL
return values against -1 to be future proof.

8 files changed, 24 insertions, 24 deletions

diff --git a/ext/sleepy_penguin/epoll.c b/ext/sleepy_penguin/epoll.c
index ca19786..8e49171 100644
--- a/ext/sleepy_penguin/epoll.c
+++ b/ext/sleepy_penguin/epoll.c
@@ -106,7 +106,7 @@ static VALUE s_new(VALUE klass, VALUE _flags)
                         rb_gc();
                         fd = epoll_create1(flags);
                 }
-                if (fd == -1)
+                if (fd < 0)
                         rb_sys_fail("epoll_create1");
         }
 
@@ -150,7 +150,7 @@ static VALUE epwait_result(struct ep_per_thread *ept, int n)
         struct epoll_event *epoll_event = ept->events;
         VALUE obj_events, obj;
 
-        if (n == -1)
+        if (n < 0)
                 rb_sys_fail("epoll_wait");
 
         for (i = n; --i >= 0; epoll_event++) {
@@ -192,7 +192,7 @@ static VALUE real_epwait(struct ep_per_thread *ept)
 
         do {
                 n = (long)rb_sp_fd_region(nogvl_wait, ept, ept->fd);
-        } while (n == -1 && epoll_resume_p(expire_at, ept));
+        } while (n < 0 && epoll_resume_p(expire_at, ept));
 
         return epwait_result(ept, (int)n);
 }
diff --git a/ext/sleepy_penguin/eventfd.c b/ext/sleepy_penguin/eventfd.c
index 1713fdd..4f95b0d 100644
--- a/ext/sleepy_penguin/eventfd.c
+++ b/ext/sleepy_penguin/eventfd.c
@@ -30,12 +30,12 @@ static VALUE s_new(int argc, VALUE *argv, VALUE klass)
         flags = rb_sp_get_flags(klass, _flags, RB_SP_CLOEXEC(EFD_CLOEXEC));
 
         fd = eventfd(initval, flags);
-        if (fd == -1) {
+        if (fd < 0) {
                 if (errno == EMFILE || errno == ENFILE || errno == ENOMEM) {
                         rb_gc();
                         fd = eventfd(initval, flags);
                 }
-                if (fd == -1)
+                if (fd < 0)
                         rb_sys_fail("eventfd");
         }
 
@@ -88,7 +88,7 @@ static VALUE incr(int argc, VALUE *argv, VALUE self)
         x.val = (uint64_t)NUM2ULL(value);
 retry:
         w = (ssize_t)rb_sp_fd_region(efd_write, &x, x.fd);
-        if (w == -1) {
+        if (w < 0) {
                 if (errno == EAGAIN && RTEST(nonblock))
                         return Qfalse;
                 if (rb_sp_wait(rb_io_wait_writable, self, &x.fd))
@@ -124,7 +124,7 @@ static VALUE getvalue(int argc, VALUE *argv, VALUE self)
         RTEST(nonblock) ? rb_sp_set_nonblock(x.fd) : blocking_io_prepare(x.fd);
 retry:
         w = (ssize_t)rb_sp_fd_region(efd_read, &x, x.fd);
-        if (w == -1) {
+        if (w < 0) {
                 if (errno == EAGAIN && RTEST(nonblock))
                         return Qnil;
                 if (rb_sp_wait(rb_io_wait_readable, self, &x.fd))
diff --git a/ext/sleepy_penguin/inotify.c b/ext/sleepy_penguin/inotify.c
index 6155507..4e771a2 100644
--- a/ext/sleepy_penguin/inotify.c
+++ b/ext/sleepy_penguin/inotify.c
@@ -30,12 +30,12 @@ static VALUE s_new(int argc, VALUE *argv, VALUE klass)
         flags = rb_sp_get_flags(klass, _flags, RB_SP_CLOEXEC(IN_CLOEXEC));
 
         fd = inotify_init1(flags);
-        if (fd == -1) {
+        if (fd < 0) {
                 if (errno == EMFILE || errno == ENFILE || errno == ENOMEM) {
                         rb_gc();
                         fd = inotify_init1(flags);
                 }
-                if (fd == -1)
+                if (fd < 0)
                         rb_sys_fail("inotify_init1");
         }
 
@@ -93,7 +93,7 @@ static VALUE add_watch(VALUE self, VALUE path, VALUE vmask)
         uint32_t mask = rb_sp_get_uflags(self, vmask);
         int rc = inotify_add_watch(fd, pathname, mask);
 
-        if (rc == -1)
+        if (rc < 0)
                 rb_sys_fail("inotify_add_watch");
 
         return UINT2NUM((uint32_t)rc);
@@ -112,7 +112,7 @@ static VALUE rm_watch(VALUE self, VALUE vwd)
         int fd = rb_sp_fileno(self);
         int rc = inotify_rm_watch(fd, wd);
 
-        if (rc == -1)
+        if (rc < 0)
                 rb_sys_fail("inotify_rm_watch");
         return INT2NUM(rc);
 }
diff --git a/ext/sleepy_penguin/missing_epoll.h b/ext/sleepy_penguin/missing_epoll.h
index 09b19d3..aa55d3a 100644
--- a/ext/sleepy_penguin/missing_epoll.h
+++ b/ext/sleepy_penguin/missing_epoll.h
@@ -15,7 +15,7 @@ static int my_epoll_create1(int flags)
         if (fd < 0 || flags == 0)
                 return fd;
 
-        if ((flags & EPOLL_CLOEXEC) && (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1))
+        if ((flags & EPOLL_CLOEXEC) && (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0))
                 goto err;
         return fd;
 err:
diff --git a/ext/sleepy_penguin/missing_inotify.h b/ext/sleepy_penguin/missing_inotify.h
index 49b324e..e22250e 100644
--- a/ext/sleepy_penguin/missing_inotify.h
+++ b/ext/sleepy_penguin/missing_inotify.h
@@ -36,13 +36,13 @@ static int my_inotify_init1(int flags)
 
         if (fd < 0)
                 return fd;
-        if ((flags & IN_CLOEXEC) && (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1))
+        if ((flags & IN_CLOEXEC) && (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0))
                 goto fcntl_err;
         if (flags & IN_NONBLOCK) {
                 tmp = fcntl(fd, F_GETFL);
                 if (tmp == -1)
                         goto fcntl_err;
-                if ((fcntl(fd, F_SETFL, tmp | O_NONBLOCK) != 0))
+                if ((fcntl(fd, F_SETFL, tmp | O_NONBLOCK) < 0))
                         goto fcntl_err;
         }
 
diff --git a/ext/sleepy_penguin/signalfd.c b/ext/sleepy_penguin/signalfd.c
index ac5db68..511745c 100644
--- a/ext/sleepy_penguin/signalfd.c
+++ b/ext/sleepy_penguin/signalfd.c
@@ -97,7 +97,7 @@ static VALUE update_bang(int argc, VALUE *argv, VALUE self)
         value2sigset(&mask, vmask);
 
         rc = signalfd(fd, &mask, flags);
-        if (rc == -1)
+        if (rc < 0)
                 rb_sys_fail("signalfd");
         return self;
 }
@@ -133,12 +133,12 @@ static VALUE s_new(int argc, VALUE *argv, VALUE klass)
         value2sigset(&mask, vmask);
 
         fd = signalfd(-1, &mask, flags);
-        if (fd == -1) {
+        if (fd < 0) {
                 if (errno == EMFILE || errno == ENFILE || errno == ENOMEM) {
                         rb_gc();
                         fd = signalfd(-1, &mask, flags);
                 }
-                if (fd == -1)
+                if (fd < 0)
                         rb_sys_fail("signalfd");
         }
 
@@ -196,7 +196,7 @@ static VALUE sfd_take(int argc, VALUE *argv, VALUE self)
 retry:
         ssi->ssi_fd = fd;
         r = (ssize_t)rb_sp_fd_region(sfd_read, ssi, fd);
-        if (r == -1) {
+        if (r < 0) {
                 if (errno == EAGAIN && RTEST(nonblock))
                         return Qnil;
                 if (rb_sp_wait(rb_io_wait_readable, self, &fd))
diff --git a/ext/sleepy_penguin/timerfd.c b/ext/sleepy_penguin/timerfd.c
index 33ef8a7..a4f5c7d 100644
--- a/ext/sleepy_penguin/timerfd.c
+++ b/ext/sleepy_penguin/timerfd.c
@@ -30,12 +30,12 @@ static VALUE s_new(int argc, VALUE *argv, VALUE klass)
         flags = rb_sp_get_flags(klass, fl, RB_SP_CLOEXEC(TFD_CLOEXEC));
 
         fd = timerfd_create(clockid, flags);
-        if (fd == -1) {
+        if (fd < 0) {
                 if (errno == EMFILE || errno == ENFILE || errno == ENOMEM) {
                         rb_gc();
                         fd = timerfd_create(clockid, flags);
                 }
-                if (fd == -1)
+                if (fd < 0)
                         rb_sys_fail("timerfd_create");
         }
 
@@ -72,7 +72,7 @@ static VALUE settime(VALUE self, VALUE fl, VALUE interval, VALUE value)
         value2timespec(&new.it_interval, interval);
         value2timespec(&new.it_value, value);
 
-        if (timerfd_settime(fd, flags, &new, &old) == -1)
+        if (timerfd_settime(fd, flags, &new, &old) < 0)
                 rb_sys_fail("timerfd_settime");
 
         return itimerspec2ary(&old);
@@ -89,7 +89,7 @@ static VALUE gettime(VALUE self)
         int fd = rb_sp_fileno(self);
         struct itimerspec curr;
 
-        if (timerfd_gettime(fd, &curr) == -1)
+        if (timerfd_gettime(fd, &curr) < 0)
                 rb_sys_fail("timerfd_gettime");
 
         return itimerspec2ary(&curr);
@@ -126,7 +126,7 @@ static VALUE expirations(int argc, VALUE *argv, VALUE self)
                 blocking_io_prepare(fd);
 retry:
         r = (ssize_t)rb_sp_fd_region(tfd_read, &buf, fd);
-        if (r == -1) {
+        if (r < 0) {
                 if (errno == EAGAIN && RTEST(nonblock))
                         return Qnil;
                 if (rb_sp_wait(rb_io_wait_readable, self, &fd))
diff --git a/ext/sleepy_penguin/util.c b/ext/sleepy_penguin/util.c
index 2423af6..11a1b13 100644
--- a/ext/sleepy_penguin/util.c
+++ b/ext/sleepy_penguin/util.c
@@ -131,7 +131,7 @@ void rb_sp_set_nonblock(int fd)
          * anything.
          */
         flags = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
-        if (flags == -1)
+        if (flags < 0)
                 rb_sys_fail("fcntl(F_SETFL)");
 }