[PATCH] json: Avoid calling strlen(NULL)

[Anthony Towns]

On Tue, Apr 6, 2010 at 17:25, David Edmondson <dme at dme.org> wrote:
>    json: Avoid calling strlen(NULL)
>    MIME parts may have no filename, which previously resulted in calling
>    strlen(NULL).
>  char *
>  json_quote_str(const void *ctx, const char *str)
>  {
> +    if (str == NULL)
> +       return (char *)"\"\"";
> +
>     return (json_quote_chararray (ctx, str, strlen (str)));
>  }

There's already a check in json_quote_chararray for len==0, so it
might be sensible to say:

    return (json_quote_chararray (ctx, str, str != NULL ? strlen (str) : 0));

OTOH, the code in json_quote_array to deal with that does the same
thing (returns a literal string containing two quote marks), which
seems wrong -- the normal code path is to talloc to get a newly
allocated, editable string, that might be talloc_free'd later,
wouldn't it make more sense just to let the str==NULL / len==0
behaviour fall through into the normal case code?

FWIW:

commit 5b93a488221b50c02db18d86a550cb3c038c00da
Author: Anthony <aj at erisian.com.au>
Date:   Tue Apr 6 18:10:39 2010 +1000

    json: Avoid calling strlen(NULL), and always return a newly talloced array.

    MIME parts may have a no filename, which causes json_quote_str()
to be invoked
    with NULL instead of a string.

diff --git a/json.c b/json.c
index f90b0fa..5e379ef 100644
--- a/json.c
+++ b/json.c
@@ -57,9 +57,6 @@ json_quote_chararray(const void *ctx, const char
*str, const size_t len)
     size_t loop;
     size_t required;

-    if (len == 0)
-	return (char *)"\"\"";
-
     for (loop = 0, required = 0, ptr = str;
 	 loop < len;
 	 loop++, required++, ptr++) {
@@ -105,5 +102,8 @@ json_quote_chararray(const void *ctx, const char
*str, const size_t len)
 char *
 json_quote_str(const void *ctx, const char *str)
 {
+    if (str == NULL)
+        str = "";
+
     return (json_quote_chararray (ctx, str, strlen (str)));
 }



-- 
Anthony Towns <aj at erisian.com.au>