hw/nvram/fw_cfg: Let fw_cfg_add_from_generator() return boolean value

Commits b6d7e9b66f..a43770df5d simplified the error propagation.
Similarly to commit 6fd5bef10b "qom: Make functions taking Error**
return bool, not void", let fw_cfg_add_from_generator() return a
boolean value, not void.
This allow to simplify parse_fw_cfg() and fixes the error handling
issue reported by Coverity (CID 1430396):

  In parse_fw_cfg():

    Variable assigned once to a constant guards dead code.

    Local variable local_err is assigned only once, to a constant
    value, making it effectively constant throughout its scope.
    If this is not the intent, examine the logic to see if there
    is a missing assignment that would make local_err not remain
    constant.

It's the call of fw_cfg_add_from_generator():

        Error *local_err = NULL;

        fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp);
        if (local_err) {
            error_propagate(errp, local_err);
            return -1;
        }
        return 0;

If it fails, parse_fw_cfg() sets an error and returns 0, which is
wrong. Harmless, because the only caller passes &error_fatal.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Fixes: Coverity CID 1430396: 'Constant' variable guards dead code (DEADCODE)
Fixes: 6552d87c48 ("softmmu/vl: Let -fw_cfg option take a 'gen_id' argument")
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200721131911.27380-3-philmd@redhat.com>

1 files changed, 1 insertions, 5 deletions

diff --git a/softmmu/vl.c b/softmmu/vl.c
index f476ef89ed..3416241557 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2070,11 +2070,7 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)
         size = strlen(str); /* NUL terminator NOT included in fw_cfg blob */
         buf = g_memdup(str, size);
     } else if (nonempty_str(gen_id)) {
-        Error *local_err = NULL;
-
-        fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp);
-        if (local_err) {
-            error_propagate(errp, local_err);
+        if (!fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp)) {
             return -1;
         }
         return 0;