From: "nobu (Nobuyoshi Nakada)" <noreply@...>
Date: 2022-07-05T05:37:25+00:00
Subject: [ruby-core:109139] [Ruby master Bug#18893] Don't redefine memcpy(3)

Issue #18893 has been updated by nobu (Nobuyoshi Nakada).


Do we need to force the function to be inlined? 

```patch
diff --git a/include/ruby/internal/memory.h b/include/ruby/internal/memory.h
index aa3464465da..0c9fa17ee92 100644
--- a/include/ruby/internal/memory.h
+++ b/include/ruby/internal/memory.h
@@ -649,6 +649,7 @@ RBIMPL_SYMBOL_EXPORT_BEGIN()
 RBIMPL_ATTR_NOALIAS()
 RBIMPL_ATTR_NONNULL((1))
 RBIMPL_ATTR_RETURNS_NONNULL()
+RBIMPL_ATTR_FORCEINLINE()
 /* At least since 2004, glibc's <string.h> annotates memcpy to be
  * __attribute__((__nonnull__(1, 2))).  However it is safe to pass NULL to the
  * source pointer, if n is 0.  Let's wrap memcpy. */
@@ -664,7 +665,7 @@ ruby_nonempty_memcpy(void *dest, const void *src, size_t n)
 }
 RBIMPL_SYMBOL_EXPORT_END()
 #undef memcpy
-#define memcpy ruby_nonempty_memcpy
+#define memcpy(dest, src, n) ruby_nonempty_memcpy(dest, src, n)
 #endif
 
 #endif /* RBIMPL_MEMORY_H */
```

----------------------------------------
Bug #18893: Don't redefine memcpy(3)
https://bugs.ruby-lang.org/issues/18893#change-98280

* Author: alx (Alejandro Colomar)
* Status: Open
* Priority: Normal
* Assignee: shyouhei (Shyouhei Urabe)
* ruby -v: ruby 3.0.4p208 (2022-04-12 revision 3fa771dded) [x86_64-linux-gnu]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
It is Undefined Behavior, by any standard ever issued.


See what I have in my system right now:


```
alx@asus5775:/usr/include$ grepc memcpy
./string.h:43:
extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
		     size_t __n) __THROW __nonnull ((1, 2));


./x86_64-linux-gnu/ruby-3.0.0/rb_mjit_min_header-3.0.4.h:1520:
extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
       size_t __n) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__nonnull__ (1, 2)));


./x86_64-linux-gnu/ruby-3.0.0/rb_mjit_min_header-3.0.4.h:1670:
extern __inline __attribute__ ((__always_inline__)) __attribute__ ((__gnu_inline__)) __attribute__ ((__artificial__)) void *
__attribute__ ((__nothrow__ , __leaf__)) memcpy (void *__restrict __dest, const void *__restrict __src, size_t __len)
{
  return __builtin___memcpy_chk (__dest, __src, __len,
     __builtin_object_size (__dest, 0));
}


./ruby-3.0.0/ruby/internal/memory.h:278:
#define memcpy ruby_nonempty_memcpy


./x86_64-linux-gnu/ruby-3.0.0/rb_mjit_min_header-3.0.4.h:22679:
#define memcpy ruby_nonempty_memcpy


$ grepc ruby_nonempty_memcpy
./ruby-3.0.0/ruby/internal/memory.h:266:
static inline void *
ruby_nonempty_memcpy(void *dest, const void *src, size_t n)
{
    if (n) {
        return memcpy(dest, src, n);
    }
    else {
        return dest;
    }
}


./x86_64-linux-gnu/ruby-3.0.0/rb_mjit_min_header-3.0.4.h:5673:
__attribute__((__nonnull__ (1)))
__attribute__((__returns_nonnull__))
static inline void *
ruby_nonempty_memcpy(void *dest, const void *src, size_t n)
{
    if (n) {
        return memcpy(dest, src, n);
    }
    else {
        return dest;
    }
}
```

Some code that I maintain includes some ruby headers, which end up defining memcpy(3) to that thing.  Then, my code calls memcpy(3) from a function, which happens to be inline (yes, inline, not static inline, which is a horrible thing), and I get an error from the compiler, for using a static function within a non-static inline function.

So, I'd like you to please remove that definition from public headers, and refrain from redefining any ISO C functions.
If not, please define it to something not broken (and yes, static inline is broken, as it produces duplicated code when not inlined; you could use [[gnu::always_inline]] if you want to keep static, but don't).  Just C99 inline would be reasonable.  See also: <https://www.greenend.org.uk/rjk/tech/inline.html>

Thanks,

Alex



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