[Qemu-devel] [PATCH 1/2] ahci: avoid #ifdef DEBUG_AHCI bitrot

[Stefan Hajnoczi <stefanha@redhat.com>]

Debug code using #ifdef is susceptible to bitrot because the compiler
never checks the debug code.

This is easy to avoid, change the DPRINTF() macro to use if (DEBUG_AHCI)
and always give it a 0 or 1 value.

This also allows us to drop an #ifdef DEBUG_AHCI in ahci_start_dma()
since the compiler can now see the local variable is used.

The motivation for this change is a recent DEBUG_AHCI build failure due
to an outdated DPRINTF() format string.  From now on the compiler will
catch these errors.

Cc: John Snow <jsnow@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/ide/ahci.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index 61dbed1..3f1e39e 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -34,15 +34,15 @@
 #include <hw/ide/pci.h>
 #include <hw/ide/ahci.h>
 
-/* #define DEBUG_AHCI */
+#define DEBUG_AHCI 0
 
-#ifdef DEBUG_AHCI
 #define DPRINTF(port, fmt, ...) \
-do { fprintf(stderr, "ahci: %s: [%d] ", __FUNCTION__, port); \
-     fprintf(stderr, fmt, ## __VA_ARGS__); } while (0)
-#else
-#define DPRINTF(port, fmt, ...) do {} while(0)
-#endif
+do { \
+    if (DEBUG_AHCI) { \
+        fprintf(stderr, "ahci: %s: [%d] ", __func__, port); \
+        fprintf(stderr, fmt, ## __VA_ARGS__); \
+    } \
+} while (0)
 
 static void check_cmd(AHCIState *s, int port);
 static int handle_cmd(AHCIState *s,int port,int slot);
@@ -551,7 +551,7 @@ static void ahci_reset_port(AHCIState *s, int port)
 
 static void debug_print_fis(uint8_t *fis, int cmd_len)
 {
-#ifdef DEBUG_AHCI
+#if DEBUG_AHCI
     int i;
 
     fprintf(stderr, "fis:");
@@ -1126,9 +1126,7 @@ out:
 static void ahci_start_dma(IDEDMA *dma, IDEState *s,
                            BlockCompletionFunc *dma_cb)
 {
-#ifdef DEBUG_AHCI
     AHCIDevice *ad = DO_UPCAST(AHCIDevice, dma, dma);
-#endif
     DPRINTF(ad->port_no, "\n");
     s->io_buffer_offset = 0;
     dma_cb(s, 0);
-- 
2.1.0