musl/src/unistd/readlink.c

#include <unistd.h>
#include <fcntl.h>
#include "syscall.h"

ssize_t readlink(const char *restrict path, char *restrict buf, size_t bufsize)
{
#ifdef SYS_readlink
	return syscall(SYS_readlink, path, buf, bufsize);
#else
	return syscall(SYS_readlinkat, AT_FDCWD, path, buf, bufsize);
#endif
}
initial check-in, version 0.5.0 2011-02-12 05:22:29 +00:00			`#include <unistd.h>`
support linux kernel apis (new archs) with old syscalls removed such archs are expected to omit definitions of the SYS_* macros for syscalls their kernels lack from arch/$ARCH/bits/syscall.h. the preprocessor is then able to select the an appropriate implementation for affected functions. two basic strategies are used on a case-by-case basis: where the old syscalls correspond to deprecated library-level functions, the deprecated functions have been converted to wrappers for the modern function, and the modern function has fallback code (omitted at the preprocessor level on new archs) to make use of the old syscalls if the new syscall fails with ENOSYS. this also improves functionality on older kernels and eliminates the incentive to program with deprecated library-level functions for the sake of compatibility with older kernels. in other situations where the old syscalls correspond to library-level functions which are not deprecated but merely lack some new features, such as the *at functions, the old syscalls are still used on archs which support them. this may change at some point in the future if or when fallback code is added to the new functions to make them usable (possibly with reduced functionality) on old kernels. 2014-05-30 01:01:32 +00:00			`#include <fcntl.h>`
initial check-in, version 0.5.0 2011-02-12 05:22:29 +00:00			`#include "syscall.h"`

use restrict everywhere it's required by c99 and/or posix 2008 to deal with the fact that the public headers may be used with pre-c99 compilers, __restrict is used in place of restrict, and defined appropriately for any supported compiler. we also avoid the form [restrict] since older versions of gcc rejected it due to a bug in the original c99 standard, and instead use the form *restrict. 2012-09-07 02:44:55 +00:00			`ssize_t readlink(const char restrict path, char restrict buf, size_t bufsize)`
initial check-in, version 0.5.0 2011-02-12 05:22:29 +00:00			`{`
support linux kernel apis (new archs) with old syscalls removed such archs are expected to omit definitions of the SYS_* macros for syscalls their kernels lack from arch/$ARCH/bits/syscall.h. the preprocessor is then able to select the an appropriate implementation for affected functions. two basic strategies are used on a case-by-case basis: where the old syscalls correspond to deprecated library-level functions, the deprecated functions have been converted to wrappers for the modern function, and the modern function has fallback code (omitted at the preprocessor level on new archs) to make use of the old syscalls if the new syscall fails with ENOSYS. this also improves functionality on older kernels and eliminates the incentive to program with deprecated library-level functions for the sake of compatibility with older kernels. in other situations where the old syscalls correspond to library-level functions which are not deprecated but merely lack some new features, such as the *at functions, the old syscalls are still used on archs which support them. this may change at some point in the future if or when fallback code is added to the new functions to make them usable (possibly with reduced functionality) on old kernels. 2014-05-30 01:01:32 +00:00			`#ifdef SYS_readlink`
global cleanup to use the new syscall interface 2011-03-20 04:16:43 +00:00			`return syscall(SYS_readlink, path, buf, bufsize);`
support linux kernel apis (new archs) with old syscalls removed such archs are expected to omit definitions of the SYS_* macros for syscalls their kernels lack from arch/$ARCH/bits/syscall.h. the preprocessor is then able to select the an appropriate implementation for affected functions. two basic strategies are used on a case-by-case basis: where the old syscalls correspond to deprecated library-level functions, the deprecated functions have been converted to wrappers for the modern function, and the modern function has fallback code (omitted at the preprocessor level on new archs) to make use of the old syscalls if the new syscall fails with ENOSYS. this also improves functionality on older kernels and eliminates the incentive to program with deprecated library-level functions for the sake of compatibility with older kernels. in other situations where the old syscalls correspond to library-level functions which are not deprecated but merely lack some new features, such as the *at functions, the old syscalls are still used on archs which support them. this may change at some point in the future if or when fallback code is added to the new functions to make them usable (possibly with reduced functionality) on old kernels. 2014-05-30 01:01:32 +00:00			`#else`
			`return syscall(SYS_readlinkat, AT_FDCWD, path, buf, bufsize);`
			`#endif`
initial check-in, version 0.5.0 2011-02-12 05:22:29 +00:00			`}`