executor: prevent non-null expected warnings

The added test triggers warnings like these:

<stdin>: In function ‘syz_mount_image.constprop’:
<stdin>:298:3: error: argument 1 null where non-null expected [-Werror=nonnull]
In file included from <stdin>:26:0:
/usr/include/x86_64-linux-gnu/sys/stat.h:320:12: note: in a call to function ‘mkdir’ declared here
 extern int mkdir (const char *__path, __mode_t __mode)
            ^~~~~
cc1: all warnings being treated as errors

<stdin>: In function ‘syz_open_procfs.constprop’:
<stdin>:530:41: error: ‘%s’ directive argument is null [-Werror=format-truncation=]
<stdin>:85:110: note: in definition of macro ‘NONFAILING’
<stdin>:532:41: error: ‘%s’ directive argument is null [-Werror=format-truncation=]
<stdin>:85:110: note: in definition of macro ‘NONFAILING’
<stdin>:534:41: error: ‘%s’ directive argument is null [-Werror=format-truncation=]
<stdin>:85:110: note: in definition of macro ‘NONFAILING’

Use volatile for all arguments of syz_ functions to prevent
compiler from treating the arguments as constants in reproducers.

Popped up during bisection that used a repro that previously worked.
Update #501

0 files changed, 0 insertions, 0 deletions