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build: ditch ages-old atomic compatibility foo

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It's 2025, we can assume ISO C11 support in the compiler.  Just retain
the few lines needed for C++.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
This commit is contained in:
David Lamparter 2025-05-21 13:45:03 +02:00
parent 10666fb6c4
commit 78c09232e3
2 changed files with 3 additions and 246 deletions
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50
configure.ac
View file

@ -1134,10 +1134,7 @@ AC_CHECK_HEADERS([stropts.h sys/ksym.h \
AC_CHECK_LIB([atomic], [main], [LIBS="$LIBS -latomic"], [], [])
ac_stdatomic_ok=false
AC_DEFINE([FRR_AUTOCONF_ATOMIC], [1], [did autoconf checks for atomic funcs])
AC_CHECK_HEADER([stdatomic.h],[
AC_MSG_CHECKING([whether _Atomic qualifier works])
AC_LINK_IFELSE([AC_LANG_SOURCE([[
#include <stdatomic.h>
@ -1151,52 +1148,7 @@ int main(int argc, char **argv) {
ac_stdatomic_ok=true
], [
AC_MSG_RESULT([no])
])
])
AS_IF([$ac_stdatomic_ok], [true], [
AC_MSG_CHECKING([for __atomic_* builtins])
AC_LINK_IFELSE([AC_LANG_SOURCE([[
int main(int argc, char **argv) {
volatile int i = 1;
__atomic_store_n (&i, 0, __ATOMIC_RELEASE);
return __atomic_load_n (&i, __ATOMIC_ACQUIRE);
}
]])], [
AC_DEFINE([HAVE___ATOMIC], [1], [found __atomic builtins])
AC_MSG_RESULT([yes])
], [
AC_MSG_RESULT([no])
dnl FreeBSD 9 has a broken stdatomic.h where _Atomic doesn't work
AC_MSG_CHECKING([for __sync_* builtins])
AC_LINK_IFELSE([AC_LANG_SOURCE([[
int main(int argc, char **argv) {
volatile int i = 1;
__sync_fetch_and_sub (&i, 1);
return __sync_val_compare_and_swap (&i, 0, 1);
}
]])], [
AC_DEFINE([HAVE___SYNC], [1], [found __sync builtins])
AC_MSG_RESULT([yes])
AC_MSG_CHECKING([for __sync_swap builtin])
AC_LINK_IFELSE([AC_LANG_SOURCE([[
int main(int argc, char **argv) {
volatile int i = 1;
return __sync_swap (&i, 2);
}
]])], [
AC_DEFINE([HAVE___SYNC_SWAP], 1, [found __sync_swap builtin])
AC_MSG_RESULT([yes])
], [
AC_MSG_RESULT([no])
])
], [
AC_MSG_RESULT([no])
AC_MSG_FAILURE([stdatomic.h unavailable and $CC has neither __atomic nor __sync builtins])
])
AC_MSG_ERROR([building FRR requires an ISO C11 compliant compiler with atomics support])
])
])

199
lib/frratomic.h
View file

@ -6,15 +6,7 @@
#ifndef _FRRATOMIC_H
#define _FRRATOMIC_H
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#ifndef FRR_AUTOCONF_ATOMIC
#error autoconf checks for atomic functions were not properly run
#endif
/* ISO C11 */
/* C++ compatibility */
#ifdef __cplusplus
#include <stdint.h>
#include <atomic>
@ -32,195 +24,8 @@ typedef std::atomic<size_t> atomic_size_t;
typedef std::atomic<uint_fast32_t> atomic_uint_fast32_t;
typedef std::atomic<uintptr_t> atomic_uintptr_t;
#elif defined(HAVE_STDATOMIC_H)
#else
#include <stdatomic.h>
/* These are available in gcc, but not in stdatomic */
#define atomic_add_fetch_explicit __atomic_add_fetch
#define atomic_sub_fetch_explicit __atomic_sub_fetch
#define atomic_and_fetch_explicit __atomic_and_fetch
#define atomic_or_fetch_explicit __atomic_or_fetch
/* gcc 4.7 and newer */
#elif defined(HAVE___ATOMIC)
#define _Atomic volatile
#define _ATOMIC_WANT_TYPEDEFS
#define memory_order_relaxed __ATOMIC_RELAXED
#define memory_order_consume __ATOMIC_CONSUME
#define memory_order_acquire __ATOMIC_ACQUIRE
#define memory_order_release __ATOMIC_RELEASE
#define memory_order_acq_rel __ATOMIC_ACQ_REL
#define memory_order_seq_cst __ATOMIC_SEQ_CST
#define atomic_load_explicit __atomic_load_n
#define atomic_store_explicit __atomic_store_n
#define atomic_exchange_explicit __atomic_exchange_n
#define atomic_fetch_add_explicit __atomic_fetch_add
#define atomic_fetch_sub_explicit __atomic_fetch_sub
#define atomic_fetch_and_explicit __atomic_fetch_and
#define atomic_fetch_or_explicit __atomic_fetch_or
#define atomic_add_fetch_explicit __atomic_add_fetch
#define atomic_sub_fetch_explicit __atomic_sub_fetch
#define atomic_and_fetch_explicit __atomic_and_fetch
#define atomic_or_fetch_explicit __atomic_or_fetch
#define atomic_compare_exchange_weak_explicit(atom, expect, desire, mem1, \
mem2) \
__atomic_compare_exchange_n(atom, expect, desire, 1, mem1, mem2)
#define atomic_compare_exchange_strong_explicit(atom, expect, desire, mem1, \
mem2) \
__atomic_compare_exchange_n(atom, expect, desire, 0, mem1, mem2)
/* gcc 4.1 and newer,
* clang 3.3 (possibly older)
*
* __sync_swap isn't in gcc's documentation, but clang has it
*
* note __sync_synchronize()
*/
#elif defined(HAVE___SYNC)
#define _Atomic volatile
#define _ATOMIC_WANT_TYPEDEFS
#define memory_order_relaxed 0
#define memory_order_consume 0
#define memory_order_acquire 0
#define memory_order_release 0
#define memory_order_acq_rel 0
#define memory_order_seq_cst 0
#define atomic_load_explicit(ptr, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_fetch_and_add((ptr), 0); \
__sync_synchronize(); \
rval; \
})
#define atomic_store_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
*(ptr) = (val); \
__sync_synchronize(); \
(void)0; \
})
#ifdef HAVE___SYNC_SWAP
#define atomic_exchange_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_swap((ptr, val), 0); \
__sync_synchronize(); \
rval; \
})
#else /* !HAVE___SYNC_SWAP */
#define atomic_exchange_explicit(ptr, val, mem) \
({ \
typeof(ptr) _ptr = (ptr); \
typeof(val) _val = (val); \
__sync_synchronize(); \
typeof(*ptr) old1, old2 = __sync_fetch_and_add(_ptr, 0); \
do { \
old1 = old2; \
old2 = __sync_val_compare_and_swap(_ptr, old1, _val); \
} while (old1 != old2); \
__sync_synchronize(); \
old2; \
})
#endif /* !HAVE___SYNC_SWAP */
#define atomic_fetch_add_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_fetch_and_add((ptr), (val)); \
__sync_synchronize(); \
rval; \
})
#define atomic_fetch_sub_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_fetch_and_sub((ptr), (val)); \
__sync_synchronize(); \
rval; \
})
#define atomic_compare_exchange_strong_explicit(atom, expect, desire, mem1, \
mem2) \
({ \
typeof(atom) _atom = (atom); \
typeof(expect) _expect = (expect); \
typeof(desire) _desire = (desire); \
__sync_synchronize(); \
typeof(*atom) rval = \
__sync_val_compare_and_swap(_atom, *_expect, _desire); \
__sync_synchronize(); \
bool ret = (rval == *_expect); \
*_expect = rval; \
ret; \
})
#define atomic_compare_exchange_weak_explicit \
atomic_compare_exchange_strong_explicit
#define atomic_fetch_and_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_fetch_and_and(ptr, val); \
__sync_synchronize(); \
rval; \
})
#define atomic_fetch_or_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_fetch_and_or(ptr, val); \
__sync_synchronize(); \
rval; \
})
#define atomic_add_fetch_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_add_and_fetch((ptr), (val)); \
__sync_synchronize(); \
rval; \
})
#define atomic_sub_fetch_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_sub_and_fetch((ptr), (val)); \
__sync_synchronize(); \
rval; \
})
#define atomic_and_fetch_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_and_and_fetch(ptr, val); \
__sync_synchronize(); \
rval; \
})
#define atomic_or_fetch_explicit(ptr, val, mem) \
({ \
__sync_synchronize(); \
typeof(*ptr) rval = __sync_or_and_fetch(ptr, val); \
__sync_synchronize(); \
rval; \
})
#else /* !HAVE___ATOMIC && !HAVE_STDATOMIC_H */
#error no atomic functions...
#endif
#ifdef _ATOMIC_WANT_TYPEDEFS
#undef _ATOMIC_WANT_TYPEDEFS
#include <stdint.h>
#include <stdbool.h>
typedef _Atomic bool atomic_bool;
typedef _Atomic size_t atomic_size_t;
typedef _Atomic uint_fast32_t atomic_uint_fast32_t;
typedef _Atomic uintptr_t atomic_uintptr_t;
#endif
#endif /* _FRRATOMIC_H */