[PATCH RFC v1] caif: Use common error handling code in cfdgml_receive()

[SF Markus Elfring]

From: Markus Elfring <elfr...@users.sourceforge.net>
Date: Tue, 7 Nov 2017 11:30:25 +0100

* Adjust jump targets so that a bit of exception handling can be better
  reused at the end of this function.

* Adjust two condition checks.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfr...@users.sourceforge.net>
---

v1 - Request for comments:
I can offer another bit of information for a software development discussion. 💭

The affected source file can be compiled for the processor architecture “x86_64”
by a tool like “GCC 6.4.1+r251631-1.3” from the software distribution
“openSUSE Tumbleweed” with the following command example.

my_cc=/usr/bin/gcc-6 \
&& my_module=net/caif/cfdgml.o \
&& for XYZ in 0 s 3; do echo "   _____ $XYZ _____" \
&& my_extra="-O$XYZ" \
&& git checkout next-20171102 \
&& make -j4 CC="${my_cc}" HOSTCC="${my_cc}" EXTRA_CFLAGS="${my_extra}" 
allmodconfig "${my_module}" \
&& size "${my_module}" \
&& git checkout ':/^caif: Use common error handling code in cfdgml_receive' \
&& make -j4 CC="${my_cc}" HOSTCC="${my_cc}" EXTRA_CFLAGS="${my_extra}" 
allmodconfig "${my_module}" \
&& size "${my_module}"; done


🔮 Do you find the following differences worth for further clarification?

╔═════════╤══════╗
║ setting │ text ║
╠═════════╪══════╣
║   O0    │ -59  ║
║   Os    │ +24  ║
║   O3    │ +36  ║
╚═════════╧══════╝


 net/caif/cfdgml.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/net/caif/cfdgml.c b/net/caif/cfdgml.c
index 3bdddb32d55a..cc7b2c944bb2 100644
--- a/net/caif/cfdgml.c
+++ b/net/caif/cfdgml.c
@@ -47,18 +47,13 @@ static int cfdgml_receive(struct cflayer *layr, struct 
cfpkt *pkt)
        caif_assert(layr->receive != NULL);
        caif_assert(layr->ctrlcmd != NULL);
 
-       if (cfpkt_extr_head(pkt, &cmd, 1) < 0) {
-               pr_err("Packet is erroneous!\n");
-               cfpkt_destroy(pkt);
-               return -EPROTO;
-       }
+       if (cfpkt_extr_head(pkt, &cmd, 1))
+               goto report_packet_failure;
 
        if ((cmd & DGM_CMD_BIT) == 0) {
-               if (cfpkt_extr_head(pkt, &dgmhdr, 3) < 0) {
-                       pr_err("Packet is erroneous!\n");
-                       cfpkt_destroy(pkt);
-                       return -EPROTO;
-               }
+               if (cfpkt_extr_head(pkt, &dgmhdr, 3))
+                       goto report_packet_failure;
+
                ret = layr->up->receive(layr->up, pkt);
                return ret;
        }
@@ -66,17 +61,23 @@ static int cfdgml_receive(struct cflayer *layr, struct 
cfpkt *pkt)
        switch (cmd) {
        case DGM_FLOW_OFF:      /* FLOW OFF */
                layr->ctrlcmd(layr, CAIF_CTRLCMD_FLOW_OFF_IND, 0);
-               cfpkt_destroy(pkt);
-               return 0;
+               ret = 0;
+               goto destroy_packet;
        case DGM_FLOW_ON:       /* FLOW ON */
                layr->ctrlcmd(layr, CAIF_CTRLCMD_FLOW_ON_IND, 0);
-               cfpkt_destroy(pkt);
-               return 0;
+               ret = 0;
+               goto destroy_packet;
        default:
-               cfpkt_destroy(pkt);
                pr_info("Unknown datagram control %d (0x%x)\n", cmd, cmd);
-               return -EPROTO;
+               goto e_proto;
        }
+report_packet_failure:
+       pr_err("Packet is erroneous!\n");
+e_proto:
+       ret = -EPROTO;
+destroy_packet:
+       cfpkt_destroy(pkt);
+       return ret;
 }
 
 static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt)
-- 
2.15.0