fixed a number of crashes due to empty string arguments or uninitialized registers

* An empty but valid teco_string_t can contain NULL pointers.
  More precisely, a state's done_cb() can be invoked with such empty strings
  in case of empty string arguments.
  Also a registers get_string() can return the NULL pointer
  for existing registers with uninitialized string parts.
* In all of these cases, the language should treat "uninitialized" strings
  exactly like empty strings.
* Not doing so, resulted in a number of vulnerabilities.
  * EN$$ crashed if "_" was uninitialized
  * The ^E@q and ^ENq string building constructs would crash for existing but
    uninitialized registers q.
  * ?$ would crash
  * ESSETILEXER$$ would crash
* This is now fixed.
  Test cases have been added.
* I cannot guarantee that I have found all such cases.
  Generally, it might be wise to change our definitions and make sure that
  every teco_string_t must have an associated heap object to be valid.
  All functions returning pointer+length pairs should consequently also never
  return NULL pointers.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/glob.c b/src/glob.c
index e67df7b..6aea02f 100644
--- a/src/glob.c
+++ b/src/glob.c
@@ -46,6 +46,9 @@ TECO_DECLARE_STATE(teco_state_glob_filename);
 void
 teco_globber_init(teco_globber_t *ctx, const gchar *pattern, GFileTest test)
 {
+	if (!pattern)
+		pattern = "";
+
 	memset(ctx, 0, sizeof(*ctx));
 	ctx->test = test;
 
@@ -114,6 +117,9 @@ teco_globber_clear(teco_globber_t *ctx)
 gchar *
 teco_globber_escape_pattern(const gchar *pattern)
 {
+	if (!pattern)
+		return g_strdup("");
+
 	gsize escaped_len = 1;
 	gchar *escaped, *pout;