[Toybox] [PATCH] tar: fix warn_unused_result error.

[enh]

On Thu, Sep 2, 2021 at 9:41 AM Rob Landley <rob at landley.net> wrote:

> On 9/1/21 11:34 AM, Rob Landley wrote:
> > I thought about typecasting it to (void) but decided to wait for a
> complaint
> > because A)
> >
> "CROSS_COMPILE=~/android/android-ndk-r21d/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android-
> > make distclean defconfig toybox" didn't warn about it (obviously -Wall
> doesn't
> > mean all, that would be silly),
>
> So looking into this, there isn't a -Wunused-result or similar, it's that
> you
> have to annotate every function you want to generate this warning for with
> __attribute__((warn_unused_result)) and the NDK headers don't.
>
> Well, there's a little annotation, via:
>
> sysroot/usr/include/sys/cdefs.h has
> #define __wur __attribute__((__warn_unused_result__))
>
> Which then appears in three other files:
>
> sysroot/usr/include/stdlib.h
> sysroot/usr/include/malloc.h
> sysroot/usr/include/sys/random.h
>
> I.E.
>
> sysroot/usr/include/stdlib.h:__wur char* realpath(const char* __path, char*
> __resolved);
> sysroot/usr/include/malloc.h:void* malloc(size_t __byte_count) __mallocfunc
> __BIONIC_ALLOC_SIZE(1) __wur;
> sysroot/usr/include/malloc.h:void* calloc(size_t __item_count, size_t
> __item_size) __mallocfunc __BIONIC_ALLOC_SIZE(1,2) __wur;
> sysroot/usr/include/malloc.h:void* realloc(void* __ptr, size_t
> __byte_count)
> __BIONIC_ALLOC_SIZE(2) __wur;
> sysroot/usr/include/malloc.h:void* reallocarray(void* __ptr, size_t
> __item_count, size_t __item_size) __BIONIC_ALLOC_SIZE(2, 3) __wur
> __INTRODUCED_IN(29);
> sysroot/usr/include/malloc.h:void* memalign(size_t __alignment, size_t
> __byte_count) __mallocfunc __BIONIC_ALLOC_SIZE(2) __wur;
> sysroot/usr/include/sys/random.h:int getentropy(void* __buffer, size_t
> __buffer_size) __wur __INTRODUCED_IN(28);
> sysroot/usr/include/sys/random.h:ssize_t getrandom(void* __buffer, size_t
> __buffer_size, unsigned int __flags) __wur __INTRODUCED_IN(28);
>
> None of which is write().
>
> That's why android-ndk-r21d isn't producing this warning.


yeah, sorry: this is for the _host_ toybox (so glibc right now).

adding more of these to bionic has been on the to-do list for years, but
turning up warnings is always a  hard slog... (see my comment about
updating the compiler in my previous response!)


> Would upgrading to a
> newer version get it,


not until i add more annotations to bionic, no :-)


> or is this more aosp-vs-ndk version skew? (And is there an
> easy way to build external packages with the AOSP prebuilt toolchain?)
>

if you actually find yourself in a situation where bionic has something
that isn't in the NDK yet, it's probably easier to update the sysroot
(which only requires an NDK manifest checkout, not a full AOSP manifest
checkout):

https://android.googlesource.com/platform/ndk/+/master/docs/PlatformApis.md#updating-the-sysroot


> Rob
> _______________________________________________
> Toybox mailing list
> Toybox at lists.landley.net
> http://lists.landley.net/listinfo.cgi/toybox-landley.net
>
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