[libvirt] [PATCH] tests: Do not ignore mode parameter in mocked open()

[Daniel P. Berrange]

On Tue, Oct 03, 2017 at 02:07:18PM +0200, Jiri Denemark wrote:
> From: Luyao Huang <lhuang at redhat.com>
> 
> This is normally not an issue since the tests which use mocked open() do
> not create files. But once coverage build is enabled, gcov_open will use
> O_CREATE and real_open will read random data rather than the actual mode
> argument.
> 
> Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
> ---
>  tests/virfilewrapper.c | 13 ++++++++++++-
>  tests/virusbmock.c     | 15 ++++++++++++++-
>  2 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/virfilewrapper.c b/tests/virfilewrapper.c
> index fede7b2e89..1d1d182708 100644
> --- a/tests/virfilewrapper.c
> +++ b/tests/virfilewrapper.c
> @@ -257,10 +257,21 @@ int open(const char *path, int flags, ...)
>  {
>      int ret = -1;
>      char *newpath = NULL;
> +    va_list ap;
> +    mode_t mode = 0;
>  
>      PATH_OVERRIDE(newpath, path);
>  
> -    ret = real_open(newpath, flags);
> +    /* The mode argument is mandatory when O_CREAT is set in flags,
> +     * otherwise the argument is ignored.
> +     */
> +    if (flags & O_CREAT) {
> +        va_start(ap, flags);
> +        mode = va_arg(ap, mode_t);
> +        va_end(ap);
> +    }

This breaks the build with clang due to use of mode_t type

virfilewrapper.c:270:27: error: second argument to 'va_arg' is of promotable type 'mode_t' (aka 'unsigned short'); this va_arg has undefined behavior because arguments will be promoted to 'int' [-Werror,-Wvarargs]

        mode = va_arg(ap, mode_t);

                          ^~~~~~

I guess we should use 'int' as the arg to va_arg(), and then cast the
result back to mode_t ?


Regards,
Daniel
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