Re: git: d5c01e1124ff - main - cdefs.h: Remove pre gcc 5.0 support

 I do welcome the cleanup, of course, just I would have defined GCC 4.2 as the breaking point instead of 5.0.
Due basically to the licensing issues, GCC 4.2 became a natural reference for GCC versions.  At some point there were vendors actually shipping FreeBSD with GCC 4.2, and it was not a huge cost to keep GCC versions above 4.2 properly discriminated.
But then you are right that it doesn't really matter that much. At least the alloc_size attributes are only defined for the FORTIFY_SOURCE in some linux libc implementation that I looked at. We define them unconditionally but I don't recall them being useful.
Just my $0.02.
Pedro.
    On Sunday, June 23, 2024 at 06:45:42 PM GMT-5, Warner Losh <imp@bsdimp.com> wrote:  
 
 Indeed. But none of the ones that I removed are affected by this quirk since they are true for clang all versions.
Warner
On Sat, Jun 22, 2024 at 12:47 PM Pedro Giffuni <pfg@freebsd.org> wrote:

 It was long ago when I last touched this but FWIW ...

clang used to report itself as GCC 4.2 and kept it's GCC extension support level consistent with that version so these version numbers were relevant.
Pedro.
    On Thursday, June 20, 2024 at 09:41:34 PM GMT-5, Warner Losh <imp@freebsd.org> wrote:  
 
 The branch main has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=d5c01e1124ffa4adb2513e7e8d708d7072dbfc75

commit d5c01e1124ffa4adb2513e7e8d708d7072dbfc75
Author:    Warner Losh <imp@FreeBSD.org>
AuthorDate: 2024-06-20 23:03:15 +0000
Commit:    Warner Losh <imp@FreeBSD.org>
CommitDate: 2024-06-21 02:41:09 +0000

    cdefs.h: Remove pre gcc 5.0 support
    
    Reviewed by:            brooks
    Differential Revision:  https://reviews.freebsd.org/D45656
    Sponsored by:          Netflix
---
 sys/sys/cdefs.h | 54 ------------------------------------------------------
 1 file changed, 54 deletions(-)

diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index a6ecdca5d8b9..43d179b82020 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -164,18 +164,9 @@
 #define    __aligned(x)    __attribute__((__aligned__(x)))
 #define    __section(x)    __attribute__((__section__(x)))
 #define    __writeonly    __unused
-#if __GNUC_PREREQ__(4, 3) || __has_attribute(__alloc_size__)
 #define    __alloc_size(x)    __attribute__((__alloc_size__(x)))
 #define    __alloc_size2(n, x)    __attribute__((__alloc_size__(n, x)))
-#else
-#define    __alloc_size(x)
-#define    __alloc_size2(n, x)
-#endif
-#if __GNUC_PREREQ__(4, 9) || __has_attribute(__alloc_align__)
 #define    __alloc_align(x)    __attribute__((__alloc_align__(x)))
-#else
-#define    __alloc_align(x)
-#endif
 
 /*
  * Keywords added in C11.
@@ -199,15 +190,6 @@
 #define    _Alignof(x)        __alignof(x)
 #endif
 
-#if !defined(__cplusplus) && !__has_extension(c_atomic) && \
-    !__has_extension(cxx_atomic) && !__GNUC_PREREQ__(4, 7)
-/*
- * No native support for _Atomic(). Place object in structure to prevent
- * most forms of direct non-atomic access.
- */
-#define    _Atomic(T)        struct { T volatile __val; }
-#endif
-
 #if defined(__cplusplus) && __cplusplus >= 201103L
 #define    _Noreturn        [[noreturn]]
 #else
@@ -218,15 +200,6 @@
 #if (defined(__cplusplus) && __cplusplus >= 201103L) || \
    __has_extension(cxx_static_assert)
 #define    _Static_assert(x, y)    static_assert(x, y)
-#elif __GNUC_PREREQ__(4,6) && !defined(__cplusplus)
-/* Nothing, gcc 4.6 and higher has _Static_assert built-in */
-#elif defined(__COUNTER__)
-#define    _Static_assert(x, y)    __Static_assert(x, __COUNTER__)
-#define    __Static_assert(x, y)    ___Static_assert(x, y)
-#define    ___Static_assert(x, y)    typedef char __assert_ ## y[(x) ? 1 : -1] \
-                __unused
-#else
-#define    _Static_assert(x, y)    struct __hack
 #endif
 #endif
 
@@ -276,7 +249,6 @@
  * void bar(int myArray[__min_size(10)]);
  */
 #if !defined(__cplusplus) && \
-    (defined(__clang__) || __GNUC_PREREQ__(4, 6)) && \
    (!defined(__STDC_VERSION__) || (__STDC_VERSION__ >= 199901))
 #define __min_size(x)    static (x)
 #else
@@ -302,17 +274,9 @@
 #define    __result_use_or_ignore_check
 #endif /* !__clang__ */
 
-#if __GNUC_PREREQ__(4, 1)
 #define    __returns_twice    __attribute__((__returns_twice__))
-#else
-#define    __returns_twice
-#endif
 
-#if __GNUC_PREREQ__(4, 6) || __has_builtin(__builtin_unreachable)
 #define    __unreachable()    __builtin_unreachable()
-#else
-#define    __unreachable()    ((void)0)
-#endif
 
 #if !defined(__STRICT_ANSI__) || __STDC_VERSION__ >= 199901
 #define    __LONG_LONG_SUPPORTED
@@ -353,33 +317,15 @@
 #define    __predict_true(exp)    __builtin_expect((exp), 1)
 #define    __predict_false(exp)    __builtin_expect((exp), 0)
 
-#if __GNUC_PREREQ__(4, 0)
 #define    __null_sentinel    __attribute__((__sentinel__))
 #define    __exported    __attribute__((__visibility__("default")))
 #define    __hidden    __attribute__((__visibility__("hidden")))
-#else
-#define    __null_sentinel
-#define    __exported
-#define    __hidden
-#endif
 
 /*
  * We define this here since <stddef.h>, <sys/queue.h>, and <sys/types.h>
  * require it.
  */
-#if __GNUC_PREREQ__(4, 1)
 #define    __offsetof(type, field)    __builtin_offsetof(type, field)
-#else
-#ifndef __cplusplus
-#define    __offsetof(type, field) \
-    ((__size_t)(__uintptr_t)((const volatile void *)&((type *)0)->field))
-#else
-#define    __offsetof(type, field)                    \
-  (__offsetof__ (reinterpret_cast <__size_t>            \
-                (&reinterpret_cast <const volatile char &>    \
-                  (static_cast<type *> (0)->field))))
-#endif
-#endif
 #define    __rangeof(type, start, end) \
     (__offsetof(type, end) - __offsetof(type, start))