Re: [Xen-devel] [PATCH v3] gcov: add new interface and 3.4 and 4.7 format support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.10.16 at 19:07, <wei.liu2@xxxxxxxxxx> wrote:
> On Wed, Oct 12, 2016 at 09:42:17AM -0600, Jan Beulich wrote:
>> >>> On 12.10.16 at 17:33, <wei.liu2@xxxxxxxxxx> wrote:
>> > On Wed, Oct 12, 2016 at 06:42:53AM -0600, Jan Beulich wrote:
>> >> >>> On 11.10.16 at 12:31, <wei.liu2@xxxxxxxxxx> wrote:
>> >> > --- /dev/null
>> >> > +++ b/xen/common/gcov/gcc_4_7.c
>> >> > @@ -0,0 +1,205 @@
>> >> > +/*
>> >> > + *  This code provides functions to handle gcc's profiling data format
>> >> > + *  introduced with gcc 4.7.
>> >> > + *
>> >> > + *  This file is based heavily on gcc_3_4.c file.
>> >> > + *
>> >> > + *  For a better understanding, refer to gcc source:
>> >> > + *  gcc/gcov-io.h
>> >> > + *  libgcc/libgcov.c
>> >> > + *
>> >> > + *  Uses gcc-internal data definitions.
>> >> > + *
>> >> > + *  Imported from Linux and modified for Xen by
>> >> > + *    Wei Liu <wei.liu2@xxxxxxxxxx>
>> >> > + */
>> >> > +
>> >> > +#include <xen/string.h>
>> >> > +
>> >> > +#include "gcov.h"
>> >> > +
>> >> > +#if GCC_VERSION < 40700
>> >> > +#error "Wrong version of GCC used to compile gcov"
>> >> > +#endif
>> >> > +
>> >> > +#if (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
>> >> > +#define GCOV_COUNTERS                   10
>> >> > +#elif __GNUC__ == 4 && __GNUC_MINOR__ >= 9
>> >> > +#define GCOV_COUNTERS                   9
>> >> > +#else
>> >> > +#define GCOV_COUNTERS                   8
>> >> > +#endif
>> >> 
>> >> I'm sorry for not having pointed this out on v2 (I had noticed it,
>> >> but then didn't finish analyzing the situation), but I'm afraid this
>> >> together with ...
>> >> 
>> >> > +struct gcov_info {
>> >> > +    unsigned int version;
>> >> > +    struct gcov_info *next;
>> >> > +    unsigned int stamp;
>> >> > +    const char *filename;
>> >> > +    void (*merge[GCOV_COUNTERS])(gcov_type *, unsigned int);
>> >> > +    unsigned int n_functions;
>> >> > +    struct gcov_fn_info **functions;
>> >> > +};
>> >> 
>> >> ... this structure's trailing fields actually getting used by the code
>> >> won't work well when changing compiler versions without cleaning
>> >> the tree. I think instead you need thin gcc_5.c and gcc_4_9.c
>> >> #define-ing their GCOV_COUNTERS and then #include-ing this
>> >> shared source file. Plus btw, I don't think gcc 5.0.x (the
>> >> development variant of 5.x) would use anything different from
>> >> 5.1.x or 5.2.x; in fact use of __GNUC_MINOR__ should not
>> >> normally be necessary anymore with gcc 5+.
>> >> 
>> > 
>> > I think you misread here: __GNUC_MINOR__ is the "x" part of 5.x.y, the
>> > "y" part is __GNUC_PATCHLEVEL__.
>> 
>> No, I didn't. From 5.x onwards the information previously carried in
>> __GNUC_PATCHLEVEL__ is now in __GNUC_MINOR__. And as much
>> as previously you would not normally need to look at the former,
>> with newer gcc you shouldn't need to look at the latter.
>> 
> 
> I can't find relevant information in GCC cpp manual.
> 
> Specifically, I look at 4.9.4 and 5.4.0 doc:
> 
> https://gcc.gnu.org/onlinedocs/gcc-4.9.4/cpp/Common-Predefined-Macros.html#Comm
>  
> on-Predefined-Macros
> https://gcc.gnu.org/onlinedocs/gcc-5.4.0/cpp/Common-Predefined-Macros.html#Comm
>  
> on-Predefined-Macros
> 
> The sections about __GNUC_* macros are identical, their semantics stay
> the same.
> 
> What did I miss?

Their change in how version numbers get used. I'm sure you've noticed
there never was a released 5.0.0 or 6.0.0, and that the stable updates
following 5.1.0 were 5.2.0, 5.3.0, etc.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel