diff --git a/expr.c b/expr.c
index ae9cd87..3eec5ae 100644
--- a/expr.c
+++ b/expr.c
@@ -182,6 +182,7 @@ static struct num compatible_sum(struct num *a, struct num *b)
 	}
 	res.type = a->type;
 	res.exponent = a->exponent;
+	res.n = 0; /* keep gcc happy */
 	return res;
 }
 
@@ -203,6 +204,7 @@ static struct num compatible_mult(struct num *a, struct num *b,
 	}
 	res.type = a->type;
 	res.exponent = exponent;
+	res.n = 0; /* keep gcc happy */
 	return res;
 }
 
diff --git a/gui.c b/gui.c
index 31e77d2..daab3cb 100644
--- a/gui.c
+++ b/gui.c
@@ -576,7 +576,7 @@ static void build_frames(GtkWidget *vbox)
 {
 	struct frame *frame;
 	GtkWidget *tab, *label, *refs, *vars;
-	int n;
+	int n = 0;
 
 	destroy_all_children(GTK_CONTAINER(vbox));
 	for (frame = frames; frame; frame = frame->next)
diff --git a/inst.c b/inst.c
index 2670247..993762f 100644
--- a/inst.c
+++ b/inst.c
@@ -126,7 +126,8 @@ int inst_select(const struct draw_ctx *ctx, struct coord pos)
 {
 	enum inst_prio prio;
 	struct inst *inst;
-	int best_dist, dist;
+	int best_dist = 0; /* keep gcc happy */
+	int dist;
 
 	deselect_outside();
 	edit_nothing();
diff --git a/util.c b/util.c
index ec2b9d6..18204f5 100644
--- a/util.c
+++ b/util.c
@@ -29,7 +29,7 @@ char *stralloc_vprintf(const char *fmt, va_list ap)
 	int n;
 
 	va_copy(aq, ap);
-	n = snprintf(NULL, 0, fmt, aq);
+	n = vsnprintf(NULL, 0, fmt, aq);
 	va_end(aq);
 	buf = alloc_size(n+1);
 	vsnprintf(buf, n+1, fmt, ap);