options: fix specifying string options without parameter

Specifying a string option with no parameter, as in "--dumpfile" with
no '=', erroneously set the corresponding variable to NULL. Fix this
to give an error about missing parameter instead.

Suboption parsing explicitly treated empty option values as if the
option had been specified with no value (no '='). Thus it was not
possible to specify empty strings as values. I think this behavior was
originally added only because of other limitations in the old
implementation. Remove it, so that suboptions now behave the same as
top-level ones in this regard.

Document the NULL-distinguishing property of bstrdup0() that the code
depends on, and also make bstrdup() behave consistently.

1 files changed, 5 insertions, 1 deletions

diff --git a/bstr.h b/bstr.h
index b3f942535e..99b7eea578 100644
--- a/bstr.h
+++ b/bstr.h
@@ -36,14 +36,18 @@ struct bstr {
 
 // demux_rtp.cpp (live555) C++ compilation workaround
 #ifndef __cplusplus
+// If str.start is NULL, return NULL.
 static inline char *bstrdup0(void *talloc_ctx, struct bstr str)
 {
     return talloc_strndup(talloc_ctx, (char *)str.start, str.len);
 }
 
+// Return start = NULL iff that is true for the original.
 static inline struct bstr bstrdup(void *talloc_ctx, struct bstr str)
 {
-    struct bstr r = { talloc_strndup(talloc_ctx, str.start, str.len), str.len };
+    struct bstr r = { NULL, str.len };
+    if (str.start)
+        r.start = talloc_memdup(talloc_ctx, str.start, str.len);
     return r;
 }