fc_sort: memory leakages

Avoid memory leakages in the fc_sort executable (now passes
all valgrind AND Clang static analyzer tests fine).

Some NULL pointer checks with or without associated error
reporting.

Some white space and comment formatting fixes.

Optimization: avoid unnecessary operations (unnecessary
memory allocation/deallocation and list copying).

Reverts 7821eb6f37 as such
trick is no longer needed, given that all memory leakages
have now been fixed.

This is the sixth version of this patch. Please do not use
the first version as it introduces a serious bug.

For reference, the original issue reported by the Cland
static analyzer is as follows:

support/fc_sort.c:494:6: warning: Potential leak of memory
pointed to by 'head'
            malloc(sizeof(file_context_bucket_t));

Signed-off-by: Guido Trentalancia <guido@trentalancia.com>
Acked-by: William Roberts <william.c.roberts@intel.com>

support/fc_sort.c

@@ -46,6 +46,9 @@ typedef struct file_context_node {
 
 void file_context_node_destroy(file_context_node_t *x)
 {
+	if (!x)
+		return;
+
 	free(x->path);
 	free(x->file_type);
 	free(x->context);
@@ -135,8 +138,6 @@ file_context_node_t *fc_merge(file_context_node_t *a,
 	file_context_node_t *temp;
 	file_context_node_t *jumpto;
 
-
-
 	/* If a is a empty list, and b is not,
 	 *  set a as b and proceed to the end. */
 	if (!a && b)
@@ -164,7 +165,6 @@ file_context_node_t *fc_merge(file_context_node_t *a,
 			       fc_compare(a_current->next,
 					  b_current) != -1) {
 
-
 				temp = a_current->next;
 				a_current->next = b_current;
 				b_current = b_current->next;
@@ -177,7 +177,6 @@ file_context_node_t *fc_merge(file_context_node_t *a,
 			a_current = jumpto;
 		}
 
-
 		/* if there is anything left in b to be inserted,
 		   put it on the end */
 		if (b_current) {
@@ -209,11 +208,12 @@ file_context_node_t *fc_merge(file_context_node_t *a,
  */
 void fc_merge_sort(file_context_bucket_t *master)
 {
-
-
 	file_context_bucket_t *current;
 	file_context_bucket_t *temp;
 
+	if (!master)
+		return;
+
 	/* Loop until master is the only bucket left
 	 * so that this will stop when master contains
 	 * the sorted list. */
@@ -222,28 +222,20 @@ void fc_merge_sort(file_context_bucket_t *master)
 
 		/* This loop merges buckets two-by-two. */
 		while (current) {
-
 			if (current->next) {
-
 				current->data =
 				    fc_merge(current->data,
 					     current->next->data);
 
-
-
 				temp = current->next;
 				current->next = current->next->next;
 
 				free(temp);
-
 			}
 
-
 			current = current->next;
 		}
 	}
-
-
 }
 
 
@@ -307,6 +299,25 @@ void fc_fill_data(file_context_node_t *fc_node)
 	}
 }
 
+
+
+/* fc_free_file_context_node_list
+ * Free the memory allocated to the linked list and its elements.
+ */
+void fc_free_file_context_node_list(struct file_context_node *node)
+{
+	struct file_context_node *next;
+
+	while (node) {
+		next = node->next;
+		file_context_node_destroy(node);
+		free(node);
+		node = next;
+	}
+}
+
+
+
 /* main
  * This program takes in two arguments, the input filename and the
  *  output filename. The input file should be syntactically correct.
@@ -328,7 +339,6 @@ int main(int argc, char *argv[])
 
 	FILE *in_file, *out_file;
 
-
 	/* Check for the correct number of command line arguments. */
 	if (argc < 2 || argc > 3) {
 		fprintf(stderr, "Usage: %s <infile> [<outfile>]\n",argv[0]);
@@ -348,24 +358,33 @@ int main(int argc, char *argv[])
 
 	/* Initialize the head of the linked list. */
 	head = current = (file_context_node_t*)malloc(sizeof(file_context_node_t));
+	if (!head) {
+		fprintf(stderr, "Error: failure allocating memory.\n");
+		return 1;
+	}
 	head->next = NULL;
+	head->path = NULL;
+	head->file_type = NULL;
+	head->context = NULL;
 
 	/* Parse the file into a file_context linked list. */
 	line_buf = NULL;
 
 	while ( getline(&line_buf, &buf_len, in_file) != -1 ){
 		line_len = strlen(line_buf);
+
 		if( line_len == 0 || line_len == 1)
 			continue;
+
 		/* Get rid of whitespace from the front of the line. */
 		for (i = 0; i < line_len; i++) {
 			if (!isspace(line_buf[i]))
 				break;
 		}
 
-
 		if (i >= line_len)
 			continue;
+
 		/* Check if the line isn't empty and isn't a comment */
 		if (line_buf[i] == '#')
 			continue;
@@ -373,7 +392,9 @@ int main(int argc, char *argv[])
 		/* We have a valid line - allocate a new node. */
 		temp = (file_context_node_t *)malloc(sizeof(file_context_node_t));
 		if (!temp) {
+			free(line_buf);
 			fprintf(stderr, "Error: failure allocating memory.\n");
+			fc_free_file_context_node_list(head);
 			return 1;
 		}
 		temp->next = NULL;
@@ -382,19 +403,15 @@ int main(int argc, char *argv[])
 		/* Parse out the regular expression from the line. */
 		start = i;
 
-
 		while (i < line_len && (!isspace(line_buf[i])))
 			i++;
 		finish = i;
 
-
 		regex_len = finish - start;
 
 		if (regex_len == 0) {
 			file_context_node_destroy(temp);
 			free(temp);
-
-
 			continue;
 		}
 
@@ -402,13 +419,14 @@ int main(int argc, char *argv[])
 		if (!temp->path) {
 			file_context_node_destroy(temp);
 			free(temp);
+			free(line_buf);
 			fprintf(stderr, "Error: failure allocating memory.\n");
+			fc_free_file_context_node_list(head);
 			return 1;
 		}
 
 		/* Get rid of whitespace after the regular expression. */
 		for (; i < line_len; i++) {
-
 			if (!isspace(line_buf[i]))
 				break;
 		}
@@ -424,14 +442,17 @@ int main(int argc, char *argv[])
 		if (line_buf[i] == '-') {
 			temp->file_type = (char *)malloc(sizeof(char) * 3);
 			if (!(temp->file_type)) {
+				file_context_node_destroy(temp);
+				free(temp);
+				free(line_buf);
 				fprintf(stderr, "Error: failure allocating memory.\n");
+				fc_free_file_context_node_list(head);
 				return 1;
 			}
 
 			if( i + 2 >= line_len ) {
 				file_context_node_destroy(temp);
 				free(temp);
-
 				continue;
 			}
 
@@ -448,7 +469,6 @@ int main(int argc, char *argv[])
 			}
 
 			if (i == line_len) {
-
 				file_context_node_destroy(temp);
 				free(temp);
 				continue;
@@ -467,7 +487,9 @@ int main(int argc, char *argv[])
 		if (!temp->context) {
 			file_context_node_destroy(temp);
 			free(temp);
+			free(line_buf);
 			fprintf(stderr, "Error: failure allocating memory.\n");
+			fc_free_file_context_node_list(head);
 			return 1;
 		}
 
@@ -480,11 +502,8 @@ int main(int argc, char *argv[])
 		current->next = temp;
 		current = current->next;
 		lines++;
-
-
-		free(line_buf);
-		line_buf = NULL;
 	}
+	free(line_buf);
 	fclose(in_file);
 
 	/* Create the bucket linked list from the earlier linked list. */
@@ -492,6 +511,12 @@ int main(int argc, char *argv[])
 	bcurrent = master =
 	    (file_context_bucket_t *)
 	    malloc(sizeof(file_context_bucket_t));
+	if (!bcurrent) {
+		printf
+		    ("Error: failure allocating memory.\n");
+		fc_free_file_context_node_list(head);
+		return -1;
+	}
 	bcurrent->next = NULL;
 	bcurrent->data = NULL;
 
@@ -512,7 +537,12 @@ int main(int argc, char *argv[])
 			if (!(bcurrent->next)) {
 				printf
 				    ("Error: failure allocating memory.\n");
-				exit(-1);
+				free(head);
+				fc_free_file_context_node_list(current);
+				fc_merge_sort(master);
+				fc_free_file_context_node_list(master->data);
+				free(master);
+				return -1;
 			}
 
 			/* Make sure the new bucket thinks it's the end of the
@@ -521,16 +551,19 @@ int main(int argc, char *argv[])
 
 			bcurrent = bcurrent->next;
 		}
-
 	}
 
 	/* Sort the bucket list. */
 	fc_merge_sort(master);
 
+	free(head);
+
 	/* Open the output file. */
 	if (output_name) {
 		if (!(out_file = fopen(output_name, "w"))) {
 			printf("Error: failure opening output file for write.\n");
+			fc_free_file_context_node_list(master->data);
+			free(master);
 			return -1;
 		}
 	} else {
@@ -539,6 +572,7 @@ int main(int argc, char *argv[])
 
 	/* Output the sorted file_context linked list to the output file. */
 	current = master->data;
+
 	while (current) {
 		/* Output the path. */
 		fprintf(out_file, "%s\t\t", current->path);
@@ -551,14 +585,10 @@ int main(int argc, char *argv[])
 		/* Output the context. */
 		fprintf(out_file, "%s\n", current->context);
 
-		/* Remove the node. */
-		temp = current;
 		current = current->next;
-
-		file_context_node_destroy(temp);
-		free(temp);
-
 	}
+
+	fc_free_file_context_node_list(master->data);
 	free(master);
 
 	if (output_name) {