Current logic on return value ('ret' variable) in main() is error
prone. The variable is initialized to EXIT_SUCCESS and then set
to EXIT_FAILURE on error paths. This makes it very easy to forget
to set the variable to indicate error when adding new error path,
as is demonstrated by handling of initialize_agent() failure.
It's simply lacking setting of the variable.

There's just one case where success should be indicated: when
dumping the config ('-D' cmd line argument).

To resolve this, initialize the variable to failure value and set
it explicitly to success value in that one specific case.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 qga/main.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/qga/main.c b/qga/main.c
index 4a695235f0..68ea7f275a 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -1579,7 +1579,7 @@ static void stop_agent(GAState *s, bool requested)
 
 int main(int argc, char **argv)
 {
-    int ret = EXIT_SUCCESS;
+    int ret = EXIT_FAILURE;
     GAState *s;
     GAConfig *config = g_new0(GAConfig, 1);
     int socket_activation;
@@ -1607,7 +1607,6 @@ int main(int argc, char **argv)
     socket_activation = check_socket_activation();
     if (socket_activation > 1) {
         g_critical("qemu-ga only supports listening on one socket");
-        ret = EXIT_FAILURE;
         goto end;
     }
     if (socket_activation) {
@@ -1631,7 +1630,6 @@ int main(int argc, char **argv)
 
         if (!config->method) {
             g_critical("unsupported listen fd type");
-            ret = EXIT_FAILURE;
             goto end;
         }
     } else if (config->channel_path == NULL) {
@@ -1643,13 +1641,13 @@ int main(int argc, char **argv)
             config->channel_path = g_strdup(QGA_SERIAL_PATH_DEFAULT);
         } else {
             g_critical("must specify a path for this channel");
-            ret = EXIT_FAILURE;
             goto end;
         }
     }
 
     if (config->dumpconf) {
         config_dump(config);
+        ret = EXIT_SUCCESS;
         goto end;
     }
 
@@ -1664,6 +1662,7 @@ int main(int argc, char **argv)
         SERVICE_TABLE_ENTRY service_table[] = {
             { (char *)QGA_SERVICE_NAME, service_main }, { NULL, NULL } };
         StartServiceCtrlDispatcher(service_table);
+        ret = EXIT_SUCCESS;
     } else {
         ret = run_agent(s);
     }
-- 
2.45.2

Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>

On Tue, Jan 7, 2025 at 4:52 PM Michal Privoznik <mprivozn@redhat.com> wrote:

> Current logic on return value ('ret' variable) in main() is error
> prone. The variable is initialized to EXIT_SUCCESS and then set
> to EXIT_FAILURE on error paths. This makes it very easy to forget
> to set the variable to indicate error when adding new error path,
> as is demonstrated by handling of initialize_agent() failure.
> It's simply lacking setting of the variable.
>
> There's just one case where success should be indicated: when
> dumping the config ('-D' cmd line argument).
>
> To resolve this, initialize the variable to failure value and set
> it explicitly to success value in that one specific case.
>
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> Reviewed-by: Ján Tomko <jtomko@redhat.com>
> ---
>  qga/main.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/qga/main.c b/qga/main.c
> index 4a695235f0..68ea7f275a 100644
> --- a/qga/main.c
> +++ b/qga/main.c
> @@ -1579,7 +1579,7 @@ static void stop_agent(GAState *s, bool requested)
>
>  int main(int argc, char **argv)
>  {
> -    int ret = EXIT_SUCCESS;
> +    int ret = EXIT_FAILURE;
>      GAState *s;
>      GAConfig *config = g_new0(GAConfig, 1);
>      int socket_activation;
> @@ -1607,7 +1607,6 @@ int main(int argc, char **argv)
>      socket_activation = check_socket_activation();
>      if (socket_activation > 1) {
>          g_critical("qemu-ga only supports listening on one socket");
> -        ret = EXIT_FAILURE;
>          goto end;
>      }
>      if (socket_activation) {
> @@ -1631,7 +1630,6 @@ int main(int argc, char **argv)
>
>          if (!config->method) {
>              g_critical("unsupported listen fd type");
> -            ret = EXIT_FAILURE;
>              goto end;
>          }
>      } else if (config->channel_path == NULL) {
> @@ -1643,13 +1641,13 @@ int main(int argc, char **argv)
>              config->channel_path = g_strdup(QGA_SERIAL_PATH_DEFAULT);
>          } else {
>              g_critical("must specify a path for this channel");
> -            ret = EXIT_FAILURE;
>              goto end;
>          }
>      }
>
>      if (config->dumpconf) {
>          config_dump(config);
> +        ret = EXIT_SUCCESS;
>          goto end;
>      }
>
> @@ -1664,6 +1662,7 @@ int main(int argc, char **argv)
>          SERVICE_TABLE_ENTRY service_table[] = {
>              { (char *)QGA_SERVICE_NAME, service_main }, { NULL, NULL } };
>          StartServiceCtrlDispatcher(service_table);
> +        ret = EXIT_SUCCESS;
>      } else {
>          ret = run_agent(s);
>      }
> --
> 2.45.2
>
>