[libcamera-devel] [PATCH] uvcvideo: Use auto variable to avoid range loop warnings

[Laurent Pinchart]

Hi Khem,

On Thu, Mar 04, 2021 at 02:00:37AM +0200, Laurent Pinchart wrote:
> On Wed, Mar 03, 2021 at 03:21:26PM -0800, Khem Raj wrote:
> > With c++17 loop range bases are defined where copy is obvious since
> > iterator returns a copy and not reference, gcc11 will emit a warning
> > about this
> > 
> > uvcvideo.cpp:432:33: error: loop variable 'name' of type 'const string&' {aka 'const std::__cxx11::basic_string<cha
> > r>&'} binds to a temporary constructed from type 'const char* const' [-Werror=range-loop-construct]
> > |   432 |         for (const std::string &name : { "idVendor", "idProduct" }) {
> > |       |                                 ^~~~
> 
> Looks like I should add gcc 11 to my build tests :-)
> 
> > Therefore making it explicit is better
> > 
> > Signed-off-by: Khem Raj <raj.khem at gmail.com>
> > ---
> >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > index 031f96e2..ef23ece7 100644
> > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > @@ -429,7 +429,7 @@ std::string PipelineHandlerUVC::generateId(const UVCCameraData *data)
> >  
> >  	/* Creata a device ID from the USB devices vendor and product ID. */
> >  	std::string deviceId;
> > -	for (const std::string &name : { "idVendor", "idProduct" }) {
> > +	for (const auto name : { "idVendor", "idProduct" }) {
> 
> What would you think about making this
> 
> 	for (const char *name : { "idVendor", "idProduct" }) {
> 
> ? We tend to only use auto when the explicit type is either impossible
> to type, or would be too long, as an explicit type makes it easier for
> the reader to know the type of the variable. I however have to say that
> using auto here since the beginning would have prevented this bug from
> happening in the first place. I'll let you decide what you think is
> best, and if you opt for const char *name, I can change this when
> applying, there's no need to resend the patch.

Would this change be OK for you ?

> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> >  		std::ifstream file(path + "/../" + name);
> >  
> >  		if (!file.is_open())

-- 
Regards,

Laurent Pinchart