Fix memory leak with redirect_link.

It should be duplicated by who's going to use it, otherwise the
duplicated string will simply leak. Add function to free it, because why
not.

This also fixes a compiler warning about losing the const qualifier.

files.c

@@ -1,4 +1,3 @@
-#define _XOPEN_SOURCE 500 /* strdup */
 #include <stdlib.h>
 #include <unistd.h>
 #include <assert.h>
@@ -125,7 +124,7 @@ size_t ssl_to_mmap(struct transmission_information ti)
                 meta++;
 
                 if (ti.header_callback) {
-                    ti.header_callback(first, strdup(meta));
+                    ti.header_callback(first, meta);
                 }
 
                 switch (first) {

gemi.c

@@ -180,7 +180,7 @@ int main(int argc, char **argv)
     // pager must always be closed before exec'ing into self
     // if redirect_link exists, should also kill pager
     // XXX: add some flag to not kill pager when performing redirection?
-    const char *redirect_link = get_gemini_redirect_link();
+    char *redirect_link = get_gemini_redirect_link();
     if (pager) wait_for_pager(pager_info, (bool)redirect_link);
 
     if (redirect_link) {
@@ -306,5 +306,6 @@ int main(int argc, char **argv)
     free(domain);
     free(path);
     free(port);
+    free_gemini_redirect_link();
     return rv;
 }

gemini.c

@@ -1,3 +1,4 @@
+#define _XOPEN_SOURCE 500 /* strdup */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -112,22 +113,30 @@ struct gemini_link_node *get_gemini_node_by_n(struct gemini_link_node *head, int
 
 static char *redirect_link = NULL;
 
-void store_gemini_redirect_link(int s, char *l)
+void store_gemini_redirect_link(int s, const char *l)
 {
     // only store URL if it is a redirect.
     // this comes from a header, so will always end with \r\n
     // cut \r
     if (s == '3') {
-        redirect_link = l;
-        *(strchr(redirect_link, '\r')) = 0;
+        redirect_link = strdup(l);
+        // if allocation fails, redirection simply won't be detected
+        if (redirect_link) {
+            *(strchr(redirect_link, '\r')) = 0;
+        }
     }
 }
 
-const char *get_gemini_redirect_link(void)
+char *get_gemini_redirect_link(void)
 {
     return redirect_link;
 }
 
+void free_gemini_redirect_link(void)
+{
+    free(redirect_link);
+}
+
 /*
  * This function joins two paths and resolves the "." ".." and "//" refs in them.
  *

gemini.h

@@ -16,8 +16,9 @@ struct gemini_link_node {
 int get_links_from_gmi(const char *, struct gemini_link_node **);
 void print_gemini_nodes(struct gemini_link_node *, FILE *);
 struct gemini_link_node *get_gemini_node_by_n(struct gemini_link_node *, int);
-void store_gemini_redirect_link(int, char *);
-const char *get_gemini_redirect_link(void);
+void store_gemini_redirect_link(int, const char *);
+char *get_gemini_redirect_link(void);
+void free_gemini_redirect_link(void);
 char *walk_gemini_path(const char *, const char *);
 
 #endif // __GEMINI_H_

purr.h

@@ -29,10 +29,13 @@ HTTP_CONN = 0,
 GEMINI_CONN
 };
 
-// callback for passing header information:
-// int - status
-// char * - relevant part of header
-typedef void (*header_callback_def)(int, char *);
+/*
+ * Callback for storing header information
+ * Args:
+ *   int status
+ *   const char *information_to_be_copied
+ */
+typedef void (*header_callback_def)(int, const char *);
 
 struct connection_information {
     br_sslio_context *ioc;