diff --git a/src/ezstream.c b/src/ezstream.c
index 5069b49..3be3d33 100644
--- a/src/ezstream.c
+++ b/src/ezstream.c
@@ -133,11 +133,6 @@ urlParse(const char *url, char **hostname, unsigned short *port,
 	size_t		 hostsiz, mountsiz;
 	const char	*errstr;
 
-	if (hostname == NULL || port == NULL || mountname == NULL) {
-		log_alert("urlParse: bad arguments");
-		abort();
-	}
-
 	if (strncmp(url, "http://", strlen("http://")) != 0) {
 		log_error("invalid <url>: not an HTTP address");
 		return (0);
@@ -385,11 +380,6 @@ getMetadataString(const char *format, metadata_t *mdata)
 {
 	char	*tmp, *str;
 
-	if (mdata == NULL) {
-		log_alert("getMetadataString: bad argument");
-		abort();
-	}
-
 	if (format == NULL)
 		return (NULL);
 
@@ -457,11 +447,6 @@ setMetadata(shout_t *shout, metadata_t *mdata, char **mdata_copy)
 	const char		*artist, *title;
 	int			 ret = SHOUTERR_SUCCESS;
 
-	if (shout == NULL) {
-		log_alert("setMetadata: bad argument");
-		abort();
-	}
-
 	if (cfg_no_metadata_updates())
 		return (SHOUTERR_SUCCESS);
 
@@ -727,11 +712,6 @@ sendStream(shout_t *shout, FILE *filepstream, const char *fileName,
 	struct timeval	 timeStamp, *startTime = tv;
 	struct timeval	 callTime, currentTime;
 
-	if (startTime == NULL) {
-		log_alert("sendStream: bad argument");
-		abort();
-	}
-
 	ez_gettimeofday((void *)&callTime);
 
 	timeStamp.tv_sec = startTime->tv_sec;
diff --git a/src/metadata.c b/src/metadata.c
index ba8890d..c0870b1 100644
--- a/src/metadata.c
+++ b/src/metadata.c
@@ -30,6 +30,8 @@
 #endif /* HAVE_VORBISFILE */
 #include <shout/shout.h>
 
+#include <assert.h>
+
 #include "log.h"
 #include "metadata.h"
 #include "util.h"
@@ -62,16 +64,16 @@ struct ID3Tag {
 	char genre;
 };
 
-metadata_t *	metadata_create(const char *);
-void		metadata_use_taglib(metadata_t *, FILE **);
-void		metadata_use_self(metadata_t *, FILE **);
-void    	metadata_clean_md(metadata_t *);
-void		metadata_get_extension(char *, size_t, const char *);
-char *		metadata_get_name(const char *);
-void		metadata_process_md(metadata_t *);
-void		metadata_normalize_string(char **);
+static metadata_t *	metadata_create(const char *);
+static void		metadata_use_taglib(metadata_t *, FILE **);
+static void		metadata_use_self(metadata_t *, FILE **);
+static void		metadata_clean_md(metadata_t *);
+static void		metadata_get_extension(char *, size_t, const char *);
+static char *		metadata_get_name(const char *);
+static void		metadata_process_md(metadata_t *);
+static void		metadata_normalize_string(char **);
 
-metadata_t *
+static metadata_t *
 metadata_create(const char *filename)
 {
 	metadata_t	*md;
@@ -83,7 +85,7 @@ metadata_create(const char *filename)
 	return (md);
 }
 
-void
+static void
 metadata_use_taglib(metadata_t *md, FILE **filep)
 #ifdef HAVE_TAGLIB
 {
@@ -92,11 +94,6 @@ metadata_use_taglib(metadata_t *md, FILE **filep)
 	const TagLib_AudioProperties	*ta;
 	char				*str;
 
-	if (md == NULL || md->filename == NULL) {
-		log_alert("metadata_use_taglib: bad arguments");
-		abort();
-	}
-
 	if (filep != NULL)
 		fclose(*filep);
 
@@ -149,7 +146,7 @@ metadata_use_taglib(metadata_t *md, FILE **filep)
 }
 #endif /* HAVE_TAGLIB */
 
-void
+static void
 metadata_use_self(metadata_t *md, FILE **filep)
 #ifdef HAVE_TAGLIB
 {
@@ -164,12 +161,6 @@ metadata_use_self(metadata_t *md, FILE **filep)
 	char		extension[25];
 	struct ID3Tag	id3tag;
 
-	if (md == NULL || filep == NULL || *filep == NULL ||
-	    md->filename == NULL) {
-		log_alert("metadata_use_self: bad arguments");
-		abort();
-	}
-
 	metadata_clean_md(md);
 	metadata_get_extension(extension, sizeof(extension), md->filename);
 
@@ -244,14 +235,9 @@ metadata_use_self(metadata_t *md, FILE **filep)
 }
 #endif /* HAVE_TAGLIB */
 
-void
+static void
 metadata_clean_md(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_clean_md: bad argument");
-		abort();
-	}
-
 	if (md->string != NULL) {
 		xfree(md->string);
 		md->string = NULL;
@@ -266,16 +252,11 @@ metadata_clean_md(metadata_t *md)
 	}
 }
 
-void
+static void
 metadata_get_extension(char *buf, size_t siz, const char *filename)
 {
 	char	 *p;
 
-	if (buf == NULL || siz == 0 || filename == NULL) {
-		log_alert("metadata_get_extension: bad arguments");
-		abort();
-	}
-
 	if ((p = strrchr(filename, '.')) != NULL)
 		strlcpy(buf, p, siz);
 	else
@@ -284,17 +265,12 @@ metadata_get_extension(char *buf, size_t siz, const char *filename)
 		*p = tolower((int)*p);
 }
 
-char *
+static char *
 metadata_get_name(const char *file)
 {
 	char	*filename = xstrdup(file);
 	char	*p1, *p2, *name;
 
-	if (file == NULL) {
-		log_alert("metadata_get_name: bad arguments");
-		abort();
-	}
-
 	if ((p1 = basename(filename)) == NULL) {
 		log_alert("basename: unexpected failure with input: %s",
 		    filename);
@@ -313,14 +289,9 @@ metadata_get_name(const char *file)
 	return (name);
 }
 
-void
+static void
 metadata_process_md(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_process_md: bad arguments");
-		abort();
-	}
-
 	if (md->string == NULL)
 		md->string = metadata_assemble_string(md);
 
@@ -331,7 +302,7 @@ metadata_process_md(metadata_t *md)
 	}
 }
 
-void
+static void
 metadata_normalize_string(char **s)
 {
 	char	*str, *cp, *tmpstr, *tp;
@@ -367,11 +338,6 @@ metadata_file(const char *filename, int normalize)
 {
 	metadata_t	*md;
 
-	if (filename == NULL || strlen(filename) == 0) {
-		log_alert("metadata_file: bad arguments");
-		abort();
-	}
-
 	md = metadata_create(filename);
 	if (!metadata_file_update(md)) {
 		metadata_free(&md);
@@ -393,11 +359,6 @@ metadata_program(const char *program, int normalize)
 	FILE		*filep;
 #endif
 
-	if (program == NULL || strlen(program) == 0) {
-		log_alert("metadata_program: bad arguments");
-		abort();
-	}
-
 	md = metadata_create(program);
 	md->program = 1;
 	md->string = xstrdup("");
@@ -456,15 +417,7 @@ metadata_file_update(metadata_t *md)
 {
 	FILE	*filep;
 
-	if (md == NULL) {
-		log_alert("metadata_file_update: bad argument");
-		abort();
-	}
-
-	if (md->program) {
-		log_alert("metadata_file_update: called with program handle");
-		abort();
-	}
+	assert(!md->program);
 
 	if ((filep = fopen(md->filename, "rb")) == NULL) {
 		log_error("%s: %s", md->filename, strerror(errno));
@@ -489,15 +442,7 @@ metadata_program_update(metadata_t *md, enum metadata_request md_req)
 	char	 buf[METADATA_MAX + 1];
 	char	 command[PATH_MAX + sizeof(" artist")];
 
-	if (md == NULL) {
-		log_alert("metadata_program_update: bad argument");
-		abort();
-	}
-
-	if (!md->program) {
-		log_alert("metadata_program_update: called with file handle");
-		abort();
-	}
+	assert(md->program);
 
 	switch (md_req) {
 	case METADATA_ALL:
@@ -600,27 +545,13 @@ metadata_program_update(metadata_t *md, enum metadata_request md_req)
 const char *
 metadata_get_string(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_get_string: bad argument");
-		abort();
-	}
-
-	if (md->string == NULL) {
-		log_alert("metadata_get_string: md->string is NULL");
-		abort();
-	}
-
+	assert(md->string);
 	return (md->string);
 }
 
 const char *
 metadata_get_artist(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_get_artist: bad argument");
-		abort();
-	}
-
 	if (md->artist == NULL)
 		return (blankString);
 	else
@@ -630,11 +561,6 @@ metadata_get_artist(metadata_t *md)
 const char *
 metadata_get_title(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_get_title: bad argument");
-		abort();
-	}
-
 	if (md->title == NULL)
 		return (blankString);
 	else
@@ -644,11 +570,6 @@ metadata_get_title(metadata_t *md)
 const char *
 metadata_get_filename(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_get_filename: bad argument");
-		abort();
-	}
-
 	if (md->filename == NULL)
 		/* Should never happen: */
 		return (blankString);
@@ -659,11 +580,6 @@ metadata_get_filename(metadata_t *md)
 int
 metadata_get_length(metadata_t *md)
 {
-	if (md == NULL) {
-		log_alert("metadata_get_length: bad argument");
-		abort();
-	}
-
 	return (md->songLen);
 }
 
@@ -673,11 +589,6 @@ metadata_assemble_string(metadata_t *md)
 	size_t	  len;
 	char	 *str;
 
-	if (md == NULL) {
-		log_alert("metadata_assemble_string: bad argument");
-		abort();
-	}
-
 	if (md->artist == NULL && md->title == NULL && md->program == 0)
 		return (metadata_get_name(md->filename));
 
diff --git a/src/playlist.c b/src/playlist.c
index e8765d2..845fc95 100644
--- a/src/playlist.c
+++ b/src/playlist.c
@@ -39,12 +39,12 @@ struct playlist {
 	char	 *prog_track;
 };
 
-playlist_t *	playlist_create(const char *);
-int		playlist_add(playlist_t *, const char *);
-unsigned int	playlist_random(void);
-const char *	playlist_run_program(playlist_t *);
+static playlist_t *	playlist_create(const char *);
+static int		playlist_add(playlist_t *, const char *);
+static unsigned int	playlist_random(void);
+static const char *	playlist_run_program(playlist_t *);
 
-playlist_t *
+static playlist_t *
 playlist_create(const char *filename)
 {
 	playlist_t	*pl;
@@ -55,16 +55,11 @@ playlist_create(const char *filename)
 	return (pl);
 }
 
-int
+static int
 playlist_add(playlist_t *pl, const char *entry)
 {
 	size_t	num;
 
-	if (pl == NULL || entry == NULL) {
-		log_alert("playlist_add: bad arguments");
-		abort();
-	}
-
 	num = pl->num + 1;
 
 	if (pl->size == 0) {
@@ -88,7 +83,7 @@ playlist_add(playlist_t *pl, const char *entry)
 	return (1);
 }
 
-unsigned int
+static unsigned int
 playlist_random(void)
 {
 	unsigned int	ret = 0;
@@ -104,6 +99,63 @@ playlist_random(void)
 	return (ret);
 }
 
+static const char *
+playlist_run_program(playlist_t *pl)
+{
+	FILE	*filep;
+	char	 buf[PATH_MAX];
+
+	if (!pl->program)
+		return (NULL);
+
+	fflush(NULL);
+	errno = 0;
+	log_debug("running command: %s", pl->filename);
+	if ((filep = popen(pl->filename, "r")) == NULL) {
+		/* popen() does not set errno reliably ... */
+		if (errno)
+			log_error("execution error: %s: %s", pl->filename,
+			    strerror(errno));
+		else
+			log_error("execution error: %s", pl->filename);
+		return (NULL);
+	}
+
+	if (fgets(buf, (int)sizeof(buf), filep) == NULL) {
+		int	errnum = errno;
+
+		pclose(filep);
+
+		if (ferror(filep)) {
+			log_alert("%s: output read error: %s", pl->filename,
+			    strerror(errnum));
+			exit(1);
+		}
+
+		/* No output (end of playlist.) */
+		return (NULL);
+	}
+
+	pclose(filep);
+
+	if (strlen(buf) == sizeof(buf) - 1) {
+		log_error("%s: output too long", pl->filename);
+		return (NULL);
+	}
+
+	buf[strcspn(buf, "\n")] = '\0';
+	buf[strcspn(buf, "\r")] = '\0';
+	if (buf[0] == '\0')
+		/* Empty line (end of playlist.) */
+		return (NULL);
+
+	if (pl->prog_track != NULL)
+		xfree(pl->prog_track);
+	pl->prog_track = xstrdup(buf);
+
+	return ((const char *)pl->prog_track);
+}
+
 void
 playlist_init(void)
 {
@@ -279,11 +331,6 @@ playlist_free(playlist_t **pl_p)
 const char *
 playlist_get_next(playlist_t *pl)
 {
-	if (pl == NULL) {
-		log_alert("playlist_get_next: bad argument");
-		abort();
-	}
-
 	if (pl->program)
 		return (playlist_run_program(pl));
 
@@ -296,11 +343,6 @@ playlist_get_next(playlist_t *pl)
 const char *
 playlist_peek_next(playlist_t *pl)
 {
-	if (pl == NULL) {
-		log_alert("playlist_peek_next: bad argument");
-		abort();
-	}
-
 	if (pl->program || pl->num == 0)
 		return (NULL);
 
@@ -310,11 +352,6 @@ playlist_peek_next(playlist_t *pl)
 void
 playlist_skip_next(playlist_t *pl)
 {
-	if (pl == NULL) {
-		log_alert("playlist_skip_next: bad argument");
-		abort();
-	}
-
 	if (pl->program || pl->num == 0)
 		return;
 
@@ -325,11 +362,6 @@ playlist_skip_next(playlist_t *pl)
 unsigned long
 playlist_get_num_items(playlist_t *pl)
 {
-	if (pl == NULL) {
-		log_alert("playlist_get_position: bad argument");
-		abort();
-	}
-
 	if (pl->program)
 		return (0);
 
@@ -339,11 +371,6 @@ playlist_get_num_items(playlist_t *pl)
 unsigned long
 playlist_get_position(playlist_t *pl)
 {
-	if (pl == NULL) {
-		log_alert("playlist_get_position: bad argument");
-		abort();
-	}
-
 	if (pl->program)
 		return (0);
 
@@ -353,11 +380,6 @@ playlist_get_position(playlist_t *pl)
 int
 playlist_set_position(playlist_t *pl, unsigned long idx)
 {
-	if (pl == NULL) {
-		log_alert("playlist_set_position: bad argument");
-		abort();
-	}
-
 	if (pl->program || idx > pl->num - 1)
 		return (0);
 
@@ -371,11 +393,6 @@ playlist_goto_entry(playlist_t *pl, const char *entry)
 {
 	unsigned long	i;
 
-	if (pl == NULL || entry == NULL) {
-		log_alert("playlist_goto_entry: bad arguments");
-		abort();
-	}
-
 	if (pl->program)
 		return (0);
 
@@ -392,11 +409,6 @@ playlist_goto_entry(playlist_t *pl, const char *entry)
 void
 playlist_rewind(playlist_t *pl)
 {
-	if (pl == NULL) {
-		log_alert("playlist_rewind: bad argument");
-		abort();
-	}
-
 	if (pl->program)
 		return;
 
@@ -408,11 +420,6 @@ playlist_reread(playlist_t **plist)
 {
 	playlist_t	*new_pl, *pl;
 
-	if (plist == NULL || *plist == NULL) {
-		log_alert("playlist_reread: bad argument");
-		abort();
-	}
-
 	pl = *plist;
 
 	if (pl->program)
@@ -436,11 +443,6 @@ playlist_shuffle(playlist_t *pl)
 	size_t	 d, i, range;
 	char	*temp;
 
-	if (pl == NULL) {
-		log_alert("playlist_shuffle: bad argument");
-		abort();
-	}
-
 	if (pl->program || pl->num < 2)
 		return;
 
@@ -466,65 +468,3 @@ playlist_shuffle(playlist_t *pl)
 		pl->list[i] = temp;
 	}
 }
-
-const char *
-playlist_run_program(playlist_t *pl)
-{
-	FILE	*filep;
-	char	 buf[PATH_MAX];
-
-	if (pl == NULL) {
-		log_alert("playlist_run_program: bad argument");
-		abort();
-	}
-
-	if (!pl->program)
-		return (NULL);
-
-	fflush(NULL);
-	errno = 0;
-	log_debug("running command: %s", pl->filename);
-	if ((filep = popen(pl->filename, "r")) == NULL) {
-		/* popen() does not set errno reliably ... */
-		if (errno)
-			log_error("execution error: %s: %s", pl->filename,
-			    strerror(errno));
-		else
-			log_error("execution error: %s", pl->filename);
-		return (NULL);
-	}
-
-	if (fgets(buf, (int)sizeof(buf), filep) == NULL) {
-		int	errnum = errno;
-
-		pclose(filep);
-
-		if (ferror(filep)) {
-			log_alert("%s: output read error: %s", pl->filename,
-			    strerror(errnum));
-			exit(1);
-		}
-
-		/* No output (end of playlist.) */
-		return (NULL);
-	}
-
-	pclose(filep);
-
-	if (strlen(buf) == sizeof(buf) - 1) {
-		log_error("%s: output too long", pl->filename);
-		return (NULL);
-	}
-
-	buf[strcspn(buf, "\n")] = '\0';
-	buf[strcspn(buf, "\r")] = '\0';
-	if (buf[0] == '\0')
-		/* Empty line (end of playlist.) */
-		return (NULL);
-
-	if (pl->prog_track != NULL)
-		xfree(pl->prog_track);
-	pl->prog_track = xstrdup(buf);
-
-	return ((const char *)pl->prog_track);
-}