fmt: disable use of stdatomic on AIX XL C and old GCC

C11 is apparently too new for these systems.

Fixes #55.
This commit is contained in:
Russ Cox 2020-05-07 08:37:51 -04:00
parent acffdcb6ee
commit c3c9c7b6ae

View file

@ -1,7 +1,28 @@
/* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
#include <stdarg.h>
#include <string.h>
/*
* As of 2020, older systems like RHEL 6 and AIX still do not have C11 atomics.
* On those systems, make the code use volatile int accesses and hope for the best.
* (Most uses of fmtinstall are not actually racing with calls to print that lookup
* formats. The code used volatile here for years without too many problems,
* even though that's technically racy. A mutex is not OK, because we want to
* be able to call print from signal handlers.)
*
* RHEL is using an old GCC (atomics were added in GCC 4.8).
* AIX is using its own IBM compiler (XL C).
*/
#if __IBMC__ || !__clang__ && __GNUC__ && (__GNUC__ < 4 || (__GNUC__==4 && __GNUC_MINOR__<8))
#warning not using C11 stdatomic on legacy system
#define _Atomic volatile
#define atomic_load(x) (*(x))
#define atomic_store(x, y) (*(x)=(y))
#define ATOMIC_VAR_INIT(x) (x)
#else
#include <stdatomic.h>
#endif
#include "plan9.h"
#include "fmt.h"
#include "fmtdef.h"