On Fri, 5 Aug 2022, Martin Storsjö wrote:

On Wed, 27 Jul 2022, Andreas Rheinhardt wrote:

Swinney, Jonathan:
This patch looks good to me. I would appreciate its merging.


 } while (0)
 #define PERF_STOP(t) do {                               \
+    int ret;                                            \
     ioctl(sysfd, PERF_EVENT_IOC_DISABLE, 0);            \
-    read(sysfd, &t, sizeof(t));                         \
+    ret = read(sysfd, &t, sizeof(t));                   \
+    (void)ret;                                          \
 } while (0)

Why do you use this extra variable instead of just casting the return
value of read to void?

Because if I just cast the return value of read to void, it still warns about it being unused, at least with GCC 9. I believe the rules for "used vs unused" for variables (where you can cast it to void to mark it as used) and "must not ignore return value" (-Wunused-result) differ. Apparently, in order to appease the compiler for a return value to not be ignored, it either has to be stored or compared.

Pushed this now.

// Martin
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