Bug 1053: Fix crash when download ends.

ELinks attempted to display a message box on file_download.term, but
it had already closed that terminal and freed the struct terminal.  To
fix this, reset file_download.term pointers to NULL when the terminal
is about to be destroyed.  Also, assert in download_data_store() that
file_download.term is either NULL or in the global "terminals" list.

Reported by أحمد المحمودي.
(cherry picked from commit 6e2476ea4d)

NEWS

@@ -8,7 +8,8 @@ file for details.
 ELinks 0.12pre2.GIT now:
 ------------------------
 
-To be released as 0.12pre3, 0.12rc1, or even 0.12.0.
+To be released as 0.12pre3, 0.12rc1, or even 0.12.0.  This branch also
+includes the changes listed under ``ELinks 0.11.5.GIT'' below.
 
 * Perl scripts can use modules that dynamically load C libraries, like
   XML::LibXML::SAX does.
@@ -17,7 +18,7 @@ ELinks 0.12pre2:
 ----------------
 
 Released on 2008-09-21.  This release also included the changes listed
-under "ELinks 0.11.5" below.
+under ``ELinks 0.11.5'' below.
 
 * bug 954, enhancement 952: Keep track of ECMAScript form and input
   objects instead of constructing new ones on every access.  When the
@@ -73,8 +74,8 @@ Bugs that should be removed from NEWS before the 0.12.0 release:
 ELinks 0.12pre1:
 ----------------
 
-Released on 2008-07-01.  This release also included all the bug fixes
+Released on 2008-07-01.  This release also included the changes listed
-of ELinks 0.11.4, but not the ones made in 0.11.4.GIT.
+under ``ELinks 0.11.4'' below.
 
 Notable new features:
 
@@ -227,6 +228,14 @@ Changes in the experimental SGML/DOM implementation:
 * enhancement: incremental parsing
 * and more.
 
+ELinks 0.11.5.GIT now:
+----------------------
+
+To be released as 0.11.6.
+
+* critical bug 1053: fix crash if a download finishes after ELinks has
+  closed the terminal from which the download was started
+
 ELinks 0.11.5:
 --------------
 

src/session/download.c

@@ -219,6 +219,29 @@ destroy_downloads(struct session *ses)
 	}
 }
 
+void
+detach_downloads_from_terminal(struct terminal *term)
+{
+	struct file_download *file_download, *next;
+
+	assert(term != NULL);
+	if_assert_failed return;
+
+	foreachsafe (file_download, next, downloads) {
+		if (file_download->term != term)
+			continue;
+
+		if (!file_download->external_handler) {
+			file_download->term = NULL;
+			if (file_download->ses
+			    && file_download->ses->tab->term == term)
+				file_download->ses = NULL;
+			continue;
+		}
+
+		abort_download(file_download);
+	}
+}
 
 static void
 download_error_dialog(struct file_download *file_download, int saved_errno)
@@ -306,6 +329,9 @@ download_data_store(struct download *download, struct file_download *file_downlo
 {
 	struct terminal *term = file_download->term;
 
+	assert_terminal_ptr_not_dangling(term);
+	if_assert_failed term = file_download->term = NULL;
+
 	if (!term) {
 		/* No term here, so no beep. --Zas */
 		abort_download(file_download);

src/session/download.h

@@ -108,6 +108,7 @@ void create_download_file(struct terminal *, unsigned char *, unsigned char **,
 
 void abort_all_downloads(void);
 void destroy_downloads(struct session *);
+void detach_downloads_from_terminal(struct terminal *);
 
 int setup_download_handler(struct session *, struct download *, struct cache_entry *, int);
 

src/terminal/terminal.c

@@ -118,6 +118,7 @@ destroy_terminal(struct terminal *term)
 #ifdef CONFIG_BOOKMARKS
 	bookmark_auto_save_tabs(term);
 #endif
+	detach_downloads_from_terminal(term);
 
 	/* delete_window doesn't update term->current_tab, but it
 	   calls redraw_terminal, which requires term->current_tab
@@ -206,6 +207,23 @@ unblock_terminal(struct terminal *term)
 		textarea_edit(1, NULL, NULL, NULL, NULL);
 }
 
+#ifndef CONFIG_FASTMEM
+void
+assert_terminal_ptr_not_dangling(const struct terminal *suspect)
+{
+	struct terminal *term;
+
+	if (suspect == NULL)
+		return;
+
+	foreach (term, terminals) {
+		if (term == suspect)
+			return;
+	}
+
+	assertm(0, "Dangling pointer to struct terminal");
+}
+#endif /* !CONFIG_FASTMEM */
 
 static void
 exec_on_master_terminal(struct terminal *term,

src/terminal/terminal.h

@@ -178,6 +178,12 @@ void destroy_all_terminals(void);
 void exec_thread(unsigned char *, int);
 void close_handle(void *);
 
+#ifdef CONFIG_FASTMEM
+#define assert_terminal_ptr_not_dangling(suspect) ((void) 0)
+#else  /* assert() does something */
+void assert_terminal_ptr_not_dangling(const struct terminal *);
+#endif
+
 /** Operations that can be requested with do_terminal_function().
  * The interlink protocol passes these values as one byte in a
  * null-terminated string, so zero cannot be used.  */