From: "shyouhei (Shyouhei Urabe)" <noreply@...>
Date: 2022-07-19T00:40:52+00:00
Subject: [ruby-core:109238] [Ruby master Misc#18921] Remove workaround for some fixed bug (llvm.4898 & 38095)?

Issue #18921 has been updated by shyouhei (Shyouhei Urabe).


Well I'm not against deleting those parts someday, but our CI still have clang-3.9 coverage.  It seems we still need them.

We need to define supported versions of clang first.  We do so for GCC (>=4). See #18839 

----------------------------------------
Misc #18921: Remove workaround for some fixed bug (llvm.4898 & 38095)?
https://bugs.ruby-lang.org/issues/18921#change-98372

* Author: Chandler (Chandler Hen)
* Status: Open
* Priority: Normal
----------------------------------------
I notice a workaround for llvm.4898 in constant_p.h:
https://github.com/ruby/ruby/blob/master/include/ruby/internal/constant_p.h 
``` c
* Note that __builtin_constant_p can be applicable inside of inline functions,
 * according to GCC manual.  Clang lacks that feature, though.
 *
 * @see https://bugs.llvm.org/show_bug.cgi?id=4898
 * @see https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
 */
#include "ruby/internal/has/builtin.h"

/** Wraps (or simulates) `__builtin_constant_p` */
#if RBIMPL_HAS_BUILTIN(__builtin_constant_p)
# define RBIMPL_CONSTANT_P(expr) __builtin_constant_p(expr)
#else
# define RBIMPL_CONSTANT_P(expr) 0
#endif

#endif /* RBIMPL_CONSTANT_P_H */
```
and a workaround for llvm.38095 in scan_args.h:
https://github.com/ruby/ruby/blob/master/include/ruby/internal/scan_args.h
``` c
/* NOTE: Use `char *fmt` instead of `const char *fmt` because of clang's bug*/
/* https://bugs.llvm.org/show_bug.cgi?id=38095 */
# define rb_scan_args0(argc, argv, fmt, varc, vars) \
    rb_scan_args_set(RB_SCAN_ARGS_PASS_CALLED_KEYWORDS, argc, argv, \
                     rb_scan_args_n_lead(fmt), \
                     rb_scan_args_n_opt(fmt), \
                     rb_scan_args_n_trail(fmt), \
                     rb_scan_args_f_var(fmt), \
                     rb_scan_args_f_hash(fmt), \
                     rb_scan_args_f_block(fmt), \
                     (rb_scan_args_verify(fmt, varc), vars), (char *)fmt, varc)
...
```
These bugs are already marked as fixed:
bugs.llvm.org/show_bug.cgi?id=4898
bugs.llvm.org/show_bug.cgi?id=38095
Shall they be removed? 



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