Add a check for seemingly unreachable condition found by scan-build

The logic of finding the event that happend just before the created one

config.c

@@ -35,7 +35,7 @@ load_nodes_section(const config_setting_t *config_section)
 	if (length <= 0) {
 		return result;
 	}
-	result.items = calloc(length, sizeof(GraphNodeConfig));
+	result.items = T_ALLOC(length, GraphNodeConfig);
 	if (!result.items) {
 		return result;
 	}
@@ -112,7 +112,7 @@ load_channels_section(const config_setting_t *config_section)
 	if (length <= 0) {
 		return result;
 	}
-	result.items = calloc(length, sizeof(GraphChannelConfig));
+	result.items = T_ALLOC(length, GraphChannelConfig);
 	if (!result.items) {
 		return result;
 	}

defs.h

@@ -6,11 +6,12 @@
 #include <stdlib.h>
 #include <stddef.h>
 
+#define lengthof(arr) (sizeof(arr) / sizeof(*arr))
 #define containerof(ptr, contype, membpath) ((contype*)(0 ? (void)(((contype*)NULL)->membpath = *(ptr)) : (void)0, ((char *)(ptr)) - offsetof(contype, membpath)))
 // Assuming child type has a field for the base type
 // So for structs it is usually actual downcast, but for unions it is an upcast
 #define DOWNCAST(contype, basename, ptr) containerof(ptr, contype, as_##basename)
-#define lengthof(arr) (sizeof(arr) / sizeof(*arr))
+#define T_ALLOC(count, T) ((T*)calloc(count, sizeof(T)))
 
 #define DEBUG_PRINT_VALUE(x, fmt) fprintf(stderr, #x " = " fmt "\n", x); fflush(stderr)
 

events.c

@@ -1,3 +1,5 @@
+#include <stdio.h>
+#include <stdlib.h>
 #include "events.h"
 
 EventNode
@@ -32,7 +34,7 @@ event_replicate(EventNode * source, size_t count)
 EventNode *
 event_create(const EventData * content)
 {
-	EventNode * event = calloc(1, sizeof(EventNode));
+	EventNode * event = T_ALLOC(1, EventNode);
 	if (content) {
 		event->data = *content;
 		event->data.modifiers = modifier_set_copy(content->modifiers);
@@ -49,6 +51,10 @@ event_create(const EventData * content)
 		list_pos = &other->next->prev;
 	}
 	EventNode * prev = *list_pos;
+	if (!prev) {
+		fprintf(stderr, "*list_pos is NULL\n");
+		abort();
+	}
 	event->next = prev->next;
 	event->prev = prev;
 	prev->next->prev = event;

filters.c

@@ -23,7 +23,7 @@ event_filter_list_extend(EventFilterList * lst)
 	if (lst->values) {
 		new_values = reallocarray(lst->values, capacity, sizeof(EventFilter));
 	} else {
-		new_values = calloc(capacity, sizeof(EventFilter));
+		new_values = T_ALLOC(capacity, EventFilter);
 	}
 	if (!new_values) {
 		return false;

main.c

@@ -32,7 +32,7 @@ main(int argc, char ** argv)
 		exit(1);
 	}
 
-	GraphNode **nodes = calloc(loaded_config.nodes.length, sizeof(GraphNode*));
+	GraphNode **nodes = T_ALLOC(loaded_config.nodes.length, GraphNode*);
 	for (size_t i = 0; i < loaded_config.nodes.length; ++i) {
 		const char* type_name = loaded_config.nodes.items[i].type;
 		if (!type_name) {
@@ -57,7 +57,7 @@ main(int argc, char ** argv)
 		}
 	}
 
-	GraphChannel *channels = calloc(loaded_config.channels.length, sizeof(GraphChannel));
+	GraphChannel *channels = T_ALLOC(loaded_config.channels.length, GraphChannel);
 	for (size_t i = 0; i < loaded_config.channels.length; ++i) {
 		const char *node_names[2];
 		GraphNode *end_nodes[2] = {NULL, NULL};

nodes/evdev.c

@@ -70,7 +70,7 @@ handle_io(EventPositionBase * self, int fd, bool is_output)
 static GraphNode *
 create(GraphNodeSpecification * spec, GraphNodeConfig * config)
 {
-	EvdevGraphNode * node = calloc(1, sizeof(EvdevGraphNode));
+	EvdevGraphNode * node = T_ALLOC(1, EvdevGraphNode);
 	if (!node) {
 		return NULL;
 	}

nodes/getchar.c

@@ -50,7 +50,7 @@ handle_io(EventPositionBase * self, int fd, bool is_output)
 static GraphNode *
 create(GraphNodeSpecification * spec, GraphNodeConfig * config)
 {
-	GetcharGraphNode * node = calloc(1, sizeof(GetcharGraphNode));
+	GetcharGraphNode * node = T_ALLOC(1, GetcharGraphNode);
 	if (!node) {
 		return NULL;
 	}

nodes/print.c

@@ -30,7 +30,7 @@ static GraphNode *
 create(GraphNodeSpecification * spec, GraphNodeConfig * config)
 {
 	(void) config;
-	GraphNode * node = calloc(1, sizeof(GraphNode));
+	GraphNode * node = T_ALLOC(1, GraphNode);
 	if (!node) {
 		return node;
 	}

processing.c

@@ -35,8 +35,8 @@ io_subscription_list_init(IOSubscriptionList * lst, size_t capacity)
 		.fds = NULL,
 		.subscribers = NULL,
 	};
-	result.fds = calloc(capacity, sizeof(int));
+	result.fds = T_ALLOC(capacity, int);
-	result.subscribers = calloc(capacity, sizeof(IOHandling*));
+	result.subscribers = T_ALLOC(capacity, IOHandling*);
 	if (!result.fds || !result.subscribers)
 		capacity = 0;
 	result.capacity = capacity;