error: Avoid unnecessary error_propagate() after error_setg()

Replace

    error_setg(&err, ...);
    error_propagate(errp, err);

by

    error_setg(errp, ...);

Related pattern:

    if (...) {
        error_setg(&err, ...);
        goto out;
    }
    ...
 out:
    error_propagate(errp, err);
    return;

When all paths to label out are that way, replace by

    if (...) {
        error_setg(errp, ...);
        return;
    }

and delete the label along with the error_propagate().

When we have at most one other path that actually needs to propagate,
and maybe one at the end that where propagation is unnecessary, e.g.

    foo(..., &err);
    if (err) {
        goto out;
    }
    ...
    bar(..., &err);
 out:
    error_propagate(errp, err);
    return;

move the error_propagate() to where it's needed, like

    if (...) {
        foo(..., &err);
        error_propagate(errp, err);
        return;
    }
    ...
    bar(..., errp);
    return;

and transform the error_setg() as above.

In some places, the transformation results in obviously unnecessary
error_propagate().  The next few commits will eliminate them.

Bonus: the elimination of gotos will make later patches in this series
easier to review.

Candidates for conversion tracked down with this Coccinelle script:

    @@
    identifier err, errp;
    expression list args;
    @@
    -    error_setg(&err, args);
    +    error_setg(errp, args);
         ... when != err
         error_propagate(errp, err);

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200707160613.848843-34-armbru@redhat.com>

1 files changed, 6 insertions, 13 deletions

diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 5ba5632..0f49110 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -278,13 +278,10 @@ out:
 static void execute_async(DWORD WINAPI (*func)(LPVOID), LPVOID opaque,
                           Error **errp)
 {
-    Error *local_err = NULL;
-
     HANDLE thread = CreateThread(NULL, 0, func, opaque, 0, NULL);
     if (!thread) {
-        error_setg(&local_err, QERR_QGA_COMMAND_FAILED,
+        error_setg(errp, QERR_QGA_COMMAND_FAILED,
                    "failed to dispatch asynchronous command");
-        error_propagate(errp, local_err);
     }
 }
 
@@ -1270,35 +1267,31 @@ typedef enum {
 static void check_suspend_mode(GuestSuspendMode mode, Error **errp)
 {
     SYSTEM_POWER_CAPABILITIES sys_pwr_caps;
-    Error *local_err = NULL;
 
     ZeroMemory(&sys_pwr_caps, sizeof(sys_pwr_caps));
     if (!GetPwrCapabilities(&sys_pwr_caps)) {
-        error_setg(&local_err, QERR_QGA_COMMAND_FAILED,
+        error_setg(errp, QERR_QGA_COMMAND_FAILED,
                    "failed to determine guest suspend capabilities");
-        goto out;
+        return;
     }
 
     switch (mode) {
     case GUEST_SUSPEND_MODE_DISK:
         if (!sys_pwr_caps.SystemS4) {
-            error_setg(&local_err, QERR_QGA_COMMAND_FAILED,
+            error_setg(errp, QERR_QGA_COMMAND_FAILED,
                        "suspend-to-disk not supported by OS");
         }
         break;
     case GUEST_SUSPEND_MODE_RAM:
         if (!sys_pwr_caps.SystemS3) {
-            error_setg(&local_err, QERR_QGA_COMMAND_FAILED,
+            error_setg(errp, QERR_QGA_COMMAND_FAILED,
                        "suspend-to-ram not supported by OS");
         }
         break;
     default:
-        error_setg(&local_err, QERR_INVALID_PARAMETER_VALUE, "mode",
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "mode",
                    "GuestSuspendMode");
     }
-
-out:
-    error_propagate(errp, local_err);
 }
 
 static DWORD WINAPI do_suspend(LPVOID opaque)