[PATCH cgi-io 01/12] Fix warnings reported by clang-10 static analyzer

[Petr Štetiar]

Fixes following warnings:

 testing/include/libubox/blobmsg.h:222:67: warning: Null pointer passed to 1st parameter expecting 'nonnull'
         return blobmsg_add_field(buf, BLOBMSG_TYPE_STRING, name, string, strlen(string) + 1);
                                                                         ^~~~~~~~~~~~~~
 cgi-io/main.c:407:4: warning: Null pointer passed to 1st parameter expecting 'nonnull'
                         unlink(st.filename);
                         ^~~~~~~~~~~~~~~~~~~

 cgi-io/main.c:876:26: warning: Null pointer passed to 1st parameter expecting 'nonnull'
         size_t plen = 0, clen = strlen(cmd) + 1;
                                 ^~~~~~~~~~~

Signed-off-by: Petr Štetiar <ynezz at true.cz>
---
 main.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/main.c b/main.c
index 549121f94488..64f474f9283d 100644
--- a/main.c
+++ b/main.c
@@ -109,7 +109,7 @@ session_access(const char *sid, const char *scope, const char *obj, const char *
 
 	ctx = ubus_connect(NULL);
 
-	if (!ctx || ubus_lookup_id(ctx, "session", &id))
+	if (!ctx || !obj || ubus_lookup_id(ctx, "session", &id))
 		goto out;
 
 	blob_buf_init(&req, 0);
@@ -403,7 +403,7 @@ response(bool success, const char *message)
 
 		printf("\t\"failure\": [ %u, \"%s\" ]\n", errno, strerror(errno));
 
-		if (st.filefd > -1)
+		if (st.filefd > -1 && st.filename)
 			unlink(st.filename);
 	}
 
@@ -873,11 +873,16 @@ main_backup(int argc, char **argv)
 static const char *
 lookup_executable(const char *cmd)
 {
-	size_t plen = 0, clen = strlen(cmd) + 1;
+	size_t plen = 0, clen;
 	static char path[PATH_MAX];
 	char *search, *p;
 	struct stat s;
 
+	if (!cmd)
+		return NULL;
+
+	clen = strlen(cmd) + 1;
+
 	if (!stat(cmd, &s) && S_ISREG(s.st_mode))
 		return cmd;