Am Montag, 5. August 2024 um 17:54:53 MESZ hat Pali Rohár <pali.ro...@gmail.com> Folgendes geschrieben:
> On Monday 05 August 2024 23:04:21 LIU Hao wrote: > > 在 2024-08-05 20:14, Antonin Décimo 写道: > > > C99 in Annex J.5.7 Function pointer casts states: > > > 1 A pointer to an object or to void may be cast to a pointer to a > > > function, allowing data to be invoked as a function (6.5.4). > > > 2 A pointer to a function may be cast to a pointer to an object or to > > > void, allowing a function to be inspected or modified (for example, by > > > a debugger) (6.5.4) > > > > > > and MSVC, clang, and GCC implement this extension. > > > > GCC warns about it if `-Wpedantic` is specified: > > (https://gcc.godbolt.org/z/e4bh3jcvs) > > ``` > > <source>:6:12: warning: ISO C forbids conversion of function pointer > > to object pointer type [-Wpedantic] > > 6 | return (void*) fn; > > | ^ > > ``` > > > > And that's the reason for not doing that. On a system with segmented memory, > > a pointer to code may assume a different segment from a pointer to data, so > > even they may appear to hold the same numeric value, they don't point to the > > same identity. > > Ok, but if the C99 standard even defines (u)intptr_t for object pointers > only (as Antonin wrote) then compiler can throw warning also for casting > function pointer to (u)intptr_t type. Or can do it in future version... > > But now I see that casting function pointer to integer and back looks to > be more safe than casting function pointer to object pointer (and back). I thought the 'correct' way to do this is by casting to (void(*)(void)), at least that's how the gcc docu says this warning should be suppressed: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wcast-function-type Hannes _______________________________________________ Mingw-w64-public mailing list Mingw-w64-public@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mingw-w64-public
