On 12/18/20 3:42 AM, Alejandro Colomar (man-pages) wrote:
Hi Martin,
I sent you an email, but I received a "delivery failure".
If you're reading this from a list, could you answer, please?
Thanks,
Alex
On 12/14/20 11:34 PM, Alejandro Colomar (man-pages) wrote:
Hello Martin,
Thanks for the correction!
Then the prototypes that changes from 'char *' to 'void *' in r269082
were not exposed to the user, right?
I guess then those are just internal implementation where GCC did use
'char *'.
__builtin___clear_cache was added to GCC in r126535 (the __builtin_
prefix is added by the macro):
+DEF_EXT_LIB_BUILTIN (BUILT_IN_CLEAR_CACHE, "__clear_cache",
BT_FN_VOID_PTR_PTR, ATTR_NOTHROW_LIST)
The BT_FN_VOID_PTR_PTR macro describes its signature as returning
void and taking two void pointer arguments. AFAIK, this has never
changed. Contrary to that, the manual entry for the built-in added
in the same revision documented it as taking two char*. That was
corrected to void* in r269082 to match.
There's a GCC internal declaration of __clear_cache (apparently
provided in libgcc for VxWorks). It was added in r264479 and
it also used char*. This was also changed to void* in r269082
to match the built-in. Looks like this __clear_cache has just
been removed from libgcc in GCC 11:
https://gcc.gnu.org/pipermail/gcc-cvs/2020-December/338478.html
Where is the actual prototype exposed to the user declared?
Built-in functions are declared implicitly by GCC. They have no
explicit declarations like user-defined functions. The implicit
internal "declarations" are specified in the GCC internal file
gcc/builtins.def, where they are hidden behind layers of macros.
For example, on the GCC 10 branch, the declaration for
__builtin___clear_cache is here:
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/builtins.def;h=fa8b0641ab13b36f983c591a7020f6b432e5fb3d;hb=refs/heads/releases/gcc-10#l837
Martin
Thanks,
Alex
P.S.: Michael, wait for a patch revision (v6).
On 12/14/20 10:13 PM, Martin Sebor wrote:
On 12/11/20 11:14 AM, Alejandro Colomar (man-pages) via Gcc wrote:
It looks like GCC recently moved from 'char *' to 'void *'.
This SO question[1] (4 years ago) quotes the GCC docs
and they had 'char *'.
__builtin___clear_cache in GCC has always been declared to take
void*. The signature in the manual was recently corrected to match
the implementation, i.e., from char* to void*, in r269082.
Martin
Maybe Clang hasn't noticed the change.
I'll report a bug.
[1]: https://stackoverflow.com/q/35741814/6872717
On 12/9/20 8:15 PM, Alejandro Colomar (man-pages) wrote:
Hi Heinrich,
It looks like a bug (or at least an undocumented divergence from GCC) in
Clang/LLVM. Or I couldn't find the documentation for it.
Clang uses 'char *':
https://github.com/llvm/llvm-project/blob/7faf62a80bfc3a9dfe34133681fcc31f8e8d658b/clang/include/clang/Basic/Builtins.def#L583
GCC uses 'void *':
https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
I CCd Clang and GCC lists; maybe they know about that divergence.
Cheers,
Alex
On 12/9/20 7:48 PM, Heinrich Schuchardt wrote:
On 12/9/20 7:34 PM, Alejandro Colomar (man-pages) wrote:
Hi Heinrich & Michael,
What about the following?:
[
NOTES
GCC provides a similar function, which may be useful on
archi‐
tectures that lack this system call:
void __builtin___clear_cache(void *begin, void *end);
]
I just checked building with Clang/LLVM. There the arguments are of
type
(char *). See the following error output:
+arch/sandbox/cpu/cache.c:19:26: error: passing 'uint8_t *' (aka
'unsigned char *') to parameter of type 'char *' converts between
pointers to integer types with different sign [-Werror,-Wpointer-sign]
+ __builtin___clear_cache(state->ram_buf,
+ ^~~~~~~~~~~~~~
+arch/sandbox/cpu/cache.c:20:12: error: passing 'uint8_t *' (aka
'unsigned char *') to parameter of type 'char *' converts between
pointers to integer types with different sign [-Werror,-Wpointer-sign]
+ state->ram_buf + state->ram_size);
+ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Best regards
Heinrich
Cheers,
Alex
On 12/9/20 7:04 PM, Heinrich Schuchardt wrote:
Hello Michael,
function cacheflush() does not exist on many architectures.
It would have saved me a lot of time if the man-page had referenced
GCC's
void __builtin___clear_cache(void *begin, void *end)
Maybe you can add it to NOTES.
Best regards
heirnich
