diff --git a/build/GNUmakefile.example b/build/GNUmakefile.example
index f2653865..31be42ca 100644
--- a/build/GNUmakefile.example
+++ b/build/GNUmakefile.example
@@ -37,6 +37,9 @@ ifeq ($(TOOLCHAIN),gcc)
 	else
 		LDFLAGS += -Wl,-rpath,'$$ORIGIN'
 	endif
+	ifneq ($(findstring cpp-,$(EXAMPLE)),)
+		LDFLAGS += -pthread
+	endif
 else
 	# TODO is there an equivalent to -L?
 	LDFLAGS += $(OUTDIR)/libui.lib
diff --git a/common/uipriv.h b/common/uipriv.h
index e39bcf86..2c6756bd 100644
--- a/common/uipriv.h
+++ b/common/uipriv.h
@@ -19,7 +19,7 @@ extern void realbug(const char *file, const char *line, const char *func, const
 extern void _implbug(const char *file, const char *line, const char *func, const char *format, ...);
 #define implbug(...) _implbug(__FILE__, _ns(__LINE__), __func__, __VA_ARGS__)
 extern void _userbug(const char *file, const char *line, const char *func, const char *format, ...);
-#define userbug(...) _implbug(__FILE__, _ns(__LINE__), __func__, __VA_ARGS__)
+#define userbug(...) _userbug(__FILE__, _ns(__LINE__), __func__, __VA_ARGS__)
 
 // control.c
 extern uiControl *newControl(size_t size, uint32_t OSsig, uint32_t typesig, const char *typenamestr);
diff --git a/darwin/alloc.m b/darwin/alloc.m
index 9f0531ba..0ce46404 100644
--- a/darwin/alloc.m
+++ b/darwin/alloc.m
@@ -43,6 +43,7 @@ void uninitAlloc(void)
 		[str appendString:[NSString stringWithFormat:@"%p %s\n", ptr, *TYPE(ptr)]];
 	}
 	userbug("Some data was leaked; either you left a uiControl lying around or there's a bug in libui itself. Leaked data:\n%s", [str UTF8String]);
+	[str release];
 }
 
 void *uiAlloc(size_t size, const char *type)
diff --git a/darwin/area.m b/darwin/area.m
index ada4ae6d..3caf1599 100644
--- a/darwin/area.m
+++ b/darwin/area.m
@@ -335,7 +335,7 @@ int sendAreaEvents(NSEvent *e)
 void uiAreaSetSize(uiArea *a, intmax_t width, intmax_t height)
 {
 	if (!a->scrolling)
-		userbug("You cannot call uiAreaSetSize() on a non-scrolling uiArea. (uiArea: %p)", a);
+		userbug("You cannot call uiAreaSetSize() on a non-scrolling uiArea. (area: %p)", a);
 	[a->area setFrameSize:NSMakeSize(width, height)];
 }
 
@@ -347,7 +347,7 @@ void uiAreaQueueRedrawAll(uiArea *a)
 void uiAreaScrollTo(uiArea *a, double x, double y, double width, double height)
 {
 	if (!a->scrolling)
-		userbug("You cannot call uiAreaScrollTo() on a non-scrolling uiArea. (uiArea: %p)", a);
+		userbug("You cannot call uiAreaScrollTo() on a non-scrolling uiArea. (area: %p)", a);
 	[a->area scrollRectToVisible:NSMakeRect(x, y, width, height)];
 	// don't worry about the return value; it just says whether scrolling was needed
 }
diff --git a/darwin/debug.m b/darwin/debug.m
index 87467add..de6d9406 100644
--- a/darwin/debug.m
+++ b/darwin/debug.m
@@ -9,7 +9,7 @@ void realbug(const char *file, const char *line, const char *func, const char *p
 	NSString *formatted;
 
 	str = [NSMutableString new];
-	[str appendString:[NSString stringWithFormat:@"[libui] %s:%s:%s %s", file, line, func, prefix]];
+	[str appendString:[NSString stringWithFormat:@"[libui] %s:%s:%s() %s", file, line, func, prefix]];
 	formatted = [[NSString alloc] initWithFormat:[NSString stringWithUTF8String:format] arguments:ap];
 	[str appendString:formatted];
 	[formatted release];
diff --git a/unix/GNUfiles.mk b/unix/GNUfiles.mk
index 4987f177..ef83c13f 100644
--- a/unix/GNUfiles.mk
+++ b/unix/GNUfiles.mk
@@ -10,6 +10,7 @@ CFILES += \
 	unix/combobox.c \
 	unix/control.c \
 	unix/datetimepicker.c \
+	unix/debug.c \
 	unix/draw.c \
 	unix/drawmatrix.c \
 	unix/drawpath.c \
diff --git a/unix/alloc.c b/unix/alloc.c
index cb37fa10..3c43ee25 100644
--- a/unix/alloc.c
+++ b/unix/alloc.c
@@ -20,18 +20,27 @@ void initAlloc(void)
 
 static void uninitComplain(gpointer ptr, gpointer data)
 {
-	fprintf(stderr, "[libui] %p %s\n", ptr, *TYPE(ptr));
+	char **str = (char **) data;
+	char *str2;
+
+	if (*str == NULL)
+		*str = g_strdup_printf("");
+	str2 = g_strdup_printf("%s%p %s\n", *str, ptr, *TYPE(ptr));
+	g_free(*str);
+	*str = str2;
 }
 
 void uninitAlloc(void)
 {
+	char *str = NULL;
+
 	if (allocations->len == 0) {
 		g_ptr_array_free(allocations, TRUE);
 		return;
 	}
-	fprintf(stderr, "[libui] leaked allocations:\n");
-	g_ptr_array_foreach(allocations, uninitComplain, NULL);
-	complain("either you left something around or there's a bug in libui");
+	g_ptr_array_foreach(allocations, uninitComplain, &str);
+	userbug("Some data was leaked; either you left a uiControl lying around or there's a bug in libui itself. Leaked data:\n%s", str);
+	g_free(str);
 }
 
 void *uiAlloc(size_t size, const char *type)
@@ -59,7 +68,7 @@ void *uiRealloc(void *p, size_t new, const char *type)
 		memset(((uint8_t *) DATA(out)) + *s, 0, new - *s);
 	*s = new;
 	if (g_ptr_array_remove(allocations, p) == FALSE)
-		complain("%p not found in allocations array in uiRealloc()", p);
+		implbug("%p not found in allocations array in uiRealloc()", p);
 	g_ptr_array_add(allocations, out);
 	return DATA(out);
 }
@@ -67,9 +76,9 @@ void *uiRealloc(void *p, size_t new, const char *type)
 void uiFree(void *p)
 {
 	if (p == NULL)
-		complain("attempt to uiFree(NULL); there's a bug somewhere");
+		implbug("attempt to uiFree(NULL); there's a bug somewhere");
 	p = BASE(p);
 	g_free(p);
 	if (g_ptr_array_remove(allocations, p) == FALSE)
-		complain("%p not found in allocations array in uiFree()", p);
+		implbug("%p not found in allocations array in uiFree()", p);
 }
diff --git a/unix/area.c b/unix/area.c
index ee4e081c..3a420f00 100644
--- a/unix/area.c
+++ b/unix/area.c
@@ -485,7 +485,7 @@ uiUnixControlAllDefaults(uiArea)
 void uiAreaSetSize(uiArea *a, intmax_t width, intmax_t height)
 {
 	if (!a->scrolling)
-		complain("attempt to call uiAreaSetSize() on a non-scrolling uiArea");
+		userbug("You cannot call uiAreaSetSize() on a non-scrolling uiArea. (area: %p)", a);
 	a->scrollWidth = width;
 	a->scrollHeight = height;
 	gtk_widget_queue_resize(a->areaWidget);
diff --git a/unix/debug.c b/unix/debug.c
new file mode 100644
index 00000000..20a4e2d0
--- /dev/null
+++ b/unix/debug.c
@@ -0,0 +1,14 @@
+// 13 may 2016
+#include "uipriv_unix.h"
+
+// TODO don't halt on release builds
+
+void realbug(const char *file, const char *line, const char *func, const char *prefix, const char *format, va_list ap)
+{
+	char *a, *b;
+
+	a = g_strdup_printf("[libui] %s:%s:%s() %s", file, line, func, prefix);
+	b = g_strdup_vprintf(format, ap);
+	g_critical("%s%s", a, b);
+	G_BREAKPOINT();
+}
diff --git a/unix/draw.c b/unix/draw.c
index 388de7be..2d7a6367 100644
--- a/unix/draw.c
+++ b/unix/draw.c
@@ -37,7 +37,7 @@ static cairo_pattern_t *mkbrush(uiDrawBrush *b)
 //	case uiDrawBrushTypeImage:
 	}
 	if (cairo_pattern_status(pat) != CAIRO_STATUS_SUCCESS)
-		complain("error creating pattern in mkbrush(): %s",
+		implbug("error creating pattern in mkbrush(): %s",
 			cairo_status_to_string(cairo_pattern_status(pat)));
 	switch (b->Type) {
 	case uiDrawBrushTypeLinearGradient:
diff --git a/unix/drawpath.c b/unix/drawpath.c
index 1204315b..acfcc953 100644
--- a/unix/drawpath.c
+++ b/unix/drawpath.c
@@ -43,7 +43,7 @@ void uiDrawFreePath(uiDrawPath *p)
 static void add(uiDrawPath *p, struct piece *piece)
 {
 	if (p->ended)
-		complain("path ended in add()");
+		userbug("You cannot modify a uiDrawPath that has been ended. (path: %p)", p);
 	g_array_append_vals(p->pieces, piece, 1);
 }
 
@@ -145,7 +145,7 @@ void runPath(uiDrawPath *p, cairo_t *cr)
 	void (*arc)(cairo_t *, double, double, double, double, double);
 
 	if (!p->ended)
-		complain("path not ended in runPath()");
+		userbug("You cannot draw with a uiDrawPath that has not been ended. (path: %p)", p);
 	cairo_new_path(cr);
 	for (i = 0; i < p->pieces->len; i++) {
 		piece = &g_array_index(p->pieces, struct piece, i);
diff --git a/unix/menu.c b/unix/menu.c
index cf276dac..5ccb4a51 100644
--- a/unix/menu.c
+++ b/unix/menu.c
@@ -109,7 +109,7 @@ void uiMenuItemDisable(uiMenuItem *item)
 void uiMenuItemOnClicked(uiMenuItem *item, void (*f)(uiMenuItem *, uiWindow *, void *), void *data)
 {
 	if (item->type == typeQuit)
-		complain("attempt to call uiMenuItemOnClicked() on a Quit item; use uiOnShouldQuit() instead");
+		userbug("You cannot call uiMenuItemOnClicked() on a Quit item; use uiOnShouldQuit() instead.");
 	item->onClicked = f;
 	item->onClickedData = data;
 }
@@ -135,7 +135,7 @@ static uiMenuItem *newItem(uiMenu *m, int type, const char *name)
 	uiMenuItem *item;
 
 	if (menusFinalized)
-		complain("attempt to create a new menu item after menus have been finalized");
+		userbug("You cannot create a new menu item after menus have been finalized.");
 
 	item = uiNew(uiMenuItem);
 
@@ -196,7 +196,7 @@ uiMenuItem *uiMenuAppendCheckItem(uiMenu *m, const char *name)
 uiMenuItem *uiMenuAppendQuitItem(uiMenu *m)
 {
 	if (hasQuit)
-		complain("attempt to add multiple Quit menu items");
+		userbug("You cannot have multiple Quit menu items in the same program.");
 	hasQuit = TRUE;
 	newItem(m, typeSeparator, NULL);
 	return newItem(m, typeQuit, NULL);
@@ -205,7 +205,7 @@ uiMenuItem *uiMenuAppendQuitItem(uiMenu *m)
 uiMenuItem *uiMenuAppendPreferencesItem(uiMenu *m)
 {
 	if (hasPreferences)
-		complain("attempt to add multiple Preferences menu items");
+		userbug("You cannot have multiple Preferences menu items in the same program.");
 	hasPreferences = TRUE;
 	newItem(m, typeSeparator, NULL);
 	return newItem(m, typePreferences, NULL);
@@ -214,7 +214,7 @@ uiMenuItem *uiMenuAppendPreferencesItem(uiMenu *m)
 uiMenuItem *uiMenuAppendAboutItem(uiMenu *m)
 {
 	if (hasAbout)
-		complain("attempt to add multiple About menu items");
+		userbug("You cannot have multiple About menu items in the same program.");
 	hasAbout = TRUE;
 	newItem(m, typeSeparator, NULL);
 	return newItem(m, typeAbout, NULL);
@@ -230,7 +230,7 @@ uiMenu *uiNewMenu(const char *name)
 	uiMenu *m;
 
 	if (menusFinalized)
-		complain("attempt to create a new menu after menus have been finalized");
+		userbug("You cannot create a new menu after menus have been finalized.");
 	if (menus == NULL)
 		menus = g_array_new(FALSE, TRUE, sizeof (uiMenu *));
 
@@ -308,7 +308,7 @@ static void freeMenuItem(GtkWidget *widget, gpointer data)
 	item = g_array_index(fmi->items, uiMenuItem *, fmi->i);
 	w = (struct menuItemWindow *) g_hash_table_lookup(item->windows, widget);
 	if (g_hash_table_remove(item->windows, widget) == FALSE)
-		complain("GtkMenuItem %p not in menu item's item/window map", widget);
+		implbug("GtkMenuItem %p not in menu item's item/window map", widget);
 	uiFree(w);
 	fmi->i++;
 }
@@ -353,7 +353,8 @@ void uninitMenus(void)
 		for (j = 0; j < m->items->len; j++) {
 			item = g_array_index(m->items, uiMenuItem *, j);
 			if (g_hash_table_size(item->windows) != 0)
-				complain("menu item %p (%s) still has uiWindows attached; did you forget to destroy some windows?", item, item->name);
+				// TODO is this really a userbug()?
+				implbug("menu item %p (%s) still has uiWindows attached; did you forget to destroy some windows?", item, item->name);
 			g_free(item->name);
 			g_hash_table_destroy(item->windows);
 			uiFree(item);
diff --git a/unix/progressbar.c b/unix/progressbar.c
index 587bc8ad..40306e6c 100644
--- a/unix/progressbar.c
+++ b/unix/progressbar.c
@@ -12,7 +12,7 @@ uiUnixControlAllDefaults(uiProgressBar)
 void uiProgressBarSetValue(uiProgressBar *p, int value)
 {
 	if (value < 0 || value > 100)
-		complain("value %d out of range in progressbarSetValue()", value);
+		userbug("Value %d is out of range for a uiProgressBar.", value);
 	gtk_progress_bar_set_fraction(p->pbar, ((gdouble) value) / 100);
 }
 
diff --git a/unix/spinbox.c b/unix/spinbox.c
index 0f1a4f5e..433c3965 100644
--- a/unix/spinbox.c
+++ b/unix/spinbox.c
@@ -49,8 +49,9 @@ uiSpinbox *uiNewSpinbox(intmax_t min, intmax_t max)
 {
 	uiSpinbox *s;
 
+	// TODO just swap?
 	if (min >= max)
-		complain("error: min >= max in uiNewSpinbox()");
+		userbug("min >= max not allowed in uiNewSpinbox().");
 
 	uiUnixNewControl(uiSpinbox, s);
 
diff --git a/unix/util.c b/unix/util.c
index 86d89a3e..7f4f43fb 100644
--- a/unix/util.c
+++ b/unix/util.c
@@ -1,17 +1,6 @@
 // 18 april 2015
 #include "uipriv_unix.h"
 
-void complain(const char *fmt, ...)
-{
-	va_list ap;
-	char *msg;
-
-	va_start(ap, fmt);
-	msg = g_strdup_vprintf(fmt, ap);
-	va_end(ap);
-	g_error("[libui] %s\n", msg);
-}
-
 void setMargined(GtkContainer *c, int margined)
 {
 	if (margined)