diff --git a/src/os_unix.c b/src/os_unix.c
index a6d1a12..0ec48a1 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -2447,7 +2447,8 @@
 #endif
 
 /*
- * Get name of current directory into buffer 'buf' of length 'len' bytes.
+ * Get name of current directory into buffer "buf" of length "len" bytes.
+ * "len" must be at least PATH_MAX.
  * Return OK for success, FAIL for failure.
  */
     int
@@ -2516,7 +2517,7 @@
     {
 	/*
 	 * If the file name has a path, change to that directory for a moment,
-	 * and then do the getwd() (and get back to where we were).
+	 * and then get the directory (and get back to where we were).
 	 * This will get the correct path name with "../" things.
 	 */
 	if (p != NULL)
@@ -3124,7 +3125,7 @@
     p = (char_u *)getenv("PATH");
     if (p == NULL || *p == NUL)
 	return -1;
-    buf = alloc((unsigned)(STRLEN(name) + STRLEN(p) + 2));
+    buf = alloc(STRLEN(name) + STRLEN(p) + 2);
     if (buf == NULL)
 	return -1;
 
@@ -4323,7 +4324,7 @@
 
 	/* Break 'shellcmdflag' into white separated parts.  This doesn't
 	 * handle quoted strings, they are very unlikely to appear. */
-	*shcf_tofree = alloc((unsigned)STRLEN(p_shcf) + 1);
+	*shcf_tofree = alloc(STRLEN(p_shcf) + 1);
 	if (*shcf_tofree == NULL)    /* out of memory */
 	    return FAIL;
 	s = *shcf_tofree;
@@ -6899,7 +6900,7 @@
 		    && !mch_can_exe((*file)[i], NULL, !(flags & EW_SHELLCMD)))
 	    continue;
 
-	p = alloc((unsigned)(STRLEN((*file)[i]) + 1 + dir));
+	p = alloc(STRLEN((*file)[i]) + 1 + dir);
 	if (p)
 	{
 	    STRCPY(p, (*file)[i]);