Re: [RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
Hi Rasmus, On Fri, Nov 2, 2018 at 11:43 AM Rasmus Villemoes wrote: > > On 2018-11-02 11:36, Miguel Ojeda wrote: > > Hi Rasmus, > > > > On Sat, Oct 27, 2018 at 2:06 PM Miguel Ojeda > > wrote: > >> > >> I did quick check and gcc >= 4.1, clang >= 3.0, icc >= 13 compilers > >> seem to support it (or at least recognize it, even if they just ignore > >> it), so we do not need to make it optional, no? Did I miss some case? > > > > compiler-attributes landed -- do you want to do the v2 of this (i.e. > > #defining it unconditionally) or you prefer I simply fix up the patch? > > I'll wait a few more days for comments on fmtcheck(), and allow you to > do the 'optional'/'required' clarification in the meantime. I hope to > get fmtcheck() picked up for -next around -rc3 or so. Any news about fmtcheck()? The "Optional" clarification landed a few weeks ago, in case you wanted to know. Hopefully it is more clear now. Cheers, Miguel
Re: [RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
On 2018-11-02 11:36, Miguel Ojeda wrote: > Hi Rasmus, > > On Sat, Oct 27, 2018 at 2:06 PM Miguel Ojeda > wrote: >> >> I did quick check and gcc >= 4.1, clang >= 3.0, icc >= 13 compilers >> seem to support it (or at least recognize it, even if they just ignore >> it), so we do not need to make it optional, no? Did I miss some case? > > compiler-attributes landed -- do you want to do the v2 of this (i.e. > #defining it unconditionally) or you prefer I simply fix up the patch? I'll wait a few more days for comments on fmtcheck(), and allow you to do the 'optional'/'required' clarification in the meantime. I hope to get fmtcheck() picked up for -next around -rc3 or so. Rasmus
Re: [RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
Hi Rasmus, On Sat, Oct 27, 2018 at 2:06 PM Miguel Ojeda wrote: > > I did quick check and gcc >= 4.1, clang >= 3.0, icc >= 13 compilers > seem to support it (or at least recognize it, even if they just ignore > it), so we do not need to make it optional, no? Did I miss some case? compiler-attributes landed -- do you want to do the v2 of this (i.e. #defining it unconditionally) or you prefer I simply fix up the patch? (I will improve the docs as well in another patch about the "optional" naming). Cheers, Miguel
Re: [RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
On Mon, Oct 29, 2018 at 11:20 AM Rasmus Villemoes wrote: > > No idea. I think I didn't really know what was meant by > required/optional. Yeah, no worries, "optional" here is intended to mean "we cannot define it unconditionally (yet)". The word leads to confusion, I agree. I will improve the wording of the comment in the top and/or change the word after this lands. Cheers, Miguel
Re: [RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
On 2018-10-27 14:06, Miguel Ojeda wrote: > Hi Rasmus, > > On Sat, Oct 27, 2018 at 1:24 AM Rasmus Villemoes > wrote: >> >> +/* >> + * Optional > > I did quick check and gcc >= 4.1, clang >= 3.0, icc >= 13 compilers > seem to support it (or at least recognize it, even if they just ignore > it), so we do not need to make it optional, no? Did I miss some case? No idea. I think I didn't really know what was meant by required/optional. E.g. something like __aligned must be supported and honoured for correctness, while format_arg is just about getting some diagnostics, and assume_aligned just allows for certain optimizations, so it doesn't really matter whether every single compiler understands them. It does seem that both icc and clang understand format_arg and issues warnings when the template doesn't match the varargs, so in that sense we can make it "required", though it seems a little backwards to define required in terms of what the current range of compilers support. Rasmus
Re: [RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
Hi Rasmus, On Sat, Oct 27, 2018 at 1:24 AM Rasmus Villemoes wrote: > > diff --git a/include/linux/compiler_attributes.h > b/include/linux/compiler_attributes.h > index 6b28c1b7310c..08264df52322 100644 > --- a/include/linux/compiler_attributes.h > +++ b/include/linux/compiler_attributes.h > @@ -32,6 +32,7 @@ > # define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9) > # define __GCC4_has_attribute___designated_init__ 0 > # define __GCC4_has_attribute___externally_visible__ 1 > +# define __GCC4_has_attribute___format_arg__ 1 Thank you Rasmus for doing this already on top of this tree! > # define __GCC4_has_attribute___noclone__ 1 > # define __GCC4_has_attribute___optimize__1 > # define __GCC4_has_attribute___nonstring__ 0 > @@ -140,6 +141,18 @@ > #define __printf(a, b) __attribute__((__format__(printf, a, > b))) > #define __scanf(a, b) __attribute__((__format__(scanf, a, > b))) > > +/* > + * Optional I did quick check and gcc >= 4.1, clang >= 3.0, icc >= 13 compilers seem to support it (or at least recognize it, even if they just ignore it), so we do not need to make it optional, no? Did I miss some case? Thanks! Cheers, Miguel
[RFC PATCH 1/7] compiler_attributes.h: add __attribute__((format_arg)) shorthand
The __format_arg attribute tells gcc that it can use a specific argument to the annotated function as the format string for the purpose of type-checking a surrounding __printf function call. For example, assuming one has a fmtcheck function declared as const char *fmtcheck(const char *, const char *, unsigned) __format_arg(2); and this is used in sprintf(buf, fmtcheck(what->ever, "%d %lx", 0), i, m) gcc checks that the varargs (i and m) matches the second argument to the fmtcheck function, i.e. that they are (int, long). With sprintf(buf, what->ever, i, m) the compiler cannot do any type checking. Even a static inline fmtcheck() that just returns its first argument would provide documentation for which specifiers what->ever is supposed to contain, but we'll implement an actual run-time check later. Signed-off-by: Rasmus Villemoes --- include/linux/compiler_attributes.h | 13 + 1 file changed, 13 insertions(+) diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 6b28c1b7310c..08264df52322 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -32,6 +32,7 @@ # define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9) # define __GCC4_has_attribute___designated_init__ 0 # define __GCC4_has_attribute___externally_visible__ 1 +# define __GCC4_has_attribute___format_arg__ 1 # define __GCC4_has_attribute___noclone__ 1 # define __GCC4_has_attribute___optimize__1 # define __GCC4_has_attribute___nonstring__ 0 @@ -140,6 +141,18 @@ #define __printf(a, b) __attribute__((__format__(printf, a, b))) #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) +/* + * Optional + * + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format_005farg-function-attribute + * clang: apparently supported, but undocumented + */ +#if __has_attribute(__format_arg__) +# define __format_arg(n) __attribute__((__format_arg__(n))) +#else +# define __format_arg(n) +#endif + /* * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline -- 2.19.1.6.gbde171bbf5
